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v Order of a reaction: meaning, relation between order and stoichiometric coefficients in balanced equations, order as an experimental quantity, rate equation for zero order reaction

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Strictly based on the latest CISCE Curriculum

CHEMISTRY

Includes:

• ISC Solved Paper, 2018

• Solved Specimen Question Paper, 2018 issued by CISCE

• ISC Examination Paper, 2017 with Marking Scheme

(Qualitative Analysis), Issued by CISCE

• Latest Handwritten Toppers' Answers

• Previous Years' Solved Papers upto 2018

• Previous Years' Board Questions modified as per the

latest CISCE pattern for Academic Year 2018-19

• Suggestions for students by CISCE

• Topics and Concepts found Difficult/Confusing by

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• •

• •

Latest Syllabus issued by CISCE for Academic Year 2018-19 9 - 16

ISC Examination Paper, 2017 with Marking Scheme (Qualitative Analysis)

Topic 1 Classification of Solids, Crystal

Lattices and Unit Cells

Topic 2 Packing in Solids and Calculation

of Density of Unit Cell

Topic 3 Defects in Solids, Electrical and

Magnetic Properties, Band Theory

of Metal

Solutions 18-37

Topic 1 Solution, Different Measures of

Concentration of Solids in Liquids,

Solubility of Gases in Liquids, Solids

Solutions

Topic 2 Raoult's Law, Ideal and Non-ideal

Solutions

Topic 3 Colligative Properties,

Determination of Molecular Mass

of Solute, Abnormal Molecular

Mass and Van't Hoff Factor

3 Electro Chemistry 38 - 54

Topic 1 Electrochemical Cells, Redox

Reactions, Galvanic Cells, Emf

of a Cell, Standard Electrode

Potential, Nernst Equation and Electrochemical Series

Topic 2 Conductance and Kohlrausch's Law

Topic 3 Faraday's Laws of Electrolysis,

Batteries and Corrosion

4 Chemical Kinetics 55-68

Topic 1 Rate of a Chemical Reaction and

Factors Affecting Rate of Reaction

Topic 2 Order of a Reaction, Integrated

Rate Equations and Half Life of

a Reaction

Topic 3 Concept of Energy, Collision

Theory and Arrhenius Equation

5 Surface Chemistry 69 - 82

Topic 1 Adsorption, Factors Affecting

Adsorption and Absorption

Topic 2 Catalysis, its Types and Enzyme

Catalysis

Topic 3 Colloidal State

6 General Principles and Process

of Isolation of Elements 83 - 99

Topic 1 Principles and Methods of Extraction

Topic 2 Metallurgy of Aluminium, Copper,

Zinc, Iron and Silver and Uses of

Metals and their Alloys

Topic 1 Group 15 Elements (Nitrogen Family)

Topic 2 Group 16 Elements (Oxygen Family)

Topic 3 Group 17 Elements (Halogen Family)

Topic 4 Group 18 Elements (Noble Gases)

d-And f-Biock Elements 124 - 136

Topic 1 d-Biock.: 3d, 4d and Sd Series

Topic 2 f-Biock Elements

Topic 3 Preparation and Properties of

Potassium Permanganate and Potassium Dichromate

9 Coordination Compounds 137 - 148

Topic1 ConceptofComplexes, Ligands,

IU PAC Nomenclature of Mononuclear Coordination Compounds

Topic 2 Isomerism, Werner's Theory, VBT,

CFT, Stability and Importance of Coordination Compounds

10 Haloalkanesand Haloarenes 149 -166

Topic 1 Haloalk.anes

Topic 2 Haloarenes

11 Alcohols, Phenols and Ethers 167 - 188

Topic 1 Alcohols and Phenols: Methods of

Preparation, Properties and Uses

Topic 2 Ethers: Methods of Preparation,

Properties and Uses

12 Aldehydes, Ketones and Carboxylic Acids 189- 217

Topic 1 Aldehydes and Ketones: Methods

of Preparation, Properties and Uses

Topic 2 Carboxylic Acids : Methods of

Preparation, Properties and Uses

13 Organic Compounds Containing Nitrogen 218- 233

14 Biomolecules 234 - 248

Topic 1 Carbohydrates

Topic 2 Proteins, Hormones, Vitamins

and Nucleic Acids

15 Polymers

16 Chemistry in Everyday Life

249-258 259-264

DO

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(21 Oct., 1833 - 10 Dec., 1896) Business Leader, Engineer, Chemist, Scientist, Inventor, Philanthropist

Born in Stockholm, Sweden, Alfred Nobel worked at his father's arms factory as a young man Intellectually curious, he went on to experiment with chemistry and explosives In 1864, a deadly explosion killed his younger brother Deeply affected, Nobel developed a safer explosive: dynamite Nobel used his vast fortune to establish the Nobel Prizes, which has come to be known for awarding the greatest achievements throughout the world He died of a stroke in 1896.

Information in this section is sourced from various available sources Though all efforts have been made

to make sure it is trustworthy, Oswaal Books shall not be responsible for mistakes, if any

Alfred B Nobel

( 4 )

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The Indian School Certificate Examination has been designed as an examination, through the medium of English, in accordance with the recommendations of the New Education Policy 1986.

It is pursued after a two-year course of studies beyond the Indian Certificate of Secondary Education (Class 10) Examination or its equivalent.

The Council for the Indian School Certificate Examination is committed to serving the nation's children, through high quality educational endeavours, with a commitment to excellence.

'We can not always build the future for our youth, but we can build our youth for the future.'

nd

-Franklin Delano Roosevelt (32 President of USA)

With this objective in mind, we at Oswaal Books have tried to design this help-book to provide the students with a logical and easy to use tool for learning Self-study and traditional classroom learning complement one another When used together, they help students learn and retain information better We hope that this book will surely function as an excellent supplement to the existing course books and the students will be able to confidently confront the examinations.

Questions incorporated in this book follow the pattern and Marking Guidelines of the Council to guide the candidates to answer with precision This will aid students to get familiar with the examination techniques.

This book contains the content as per the prescribed Syllabus and Pattern outlined by the Council and the topics have been covered elaborately and accordingly It contains brief description of chapters and more than sufficient questions The remarkable feature is the inclusion of Answering Tips and Examiner's Comments at the end of every question, which will empower the students to comprehend their mistakes and rectify them.

This book would not have taken shape without the support of our authors and editors We would like to extend our heartfelt gratitude to them There is always a scope for improvement and any constructive suggestion will be heartily considered Together we can make this book stand in the category as 'One of the Best' Wish you Happy Learning!

-Team Oswaal

PREFACE

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( 6 )

Examination Paper 2017

l Concepts of molarity based on (grams/litre)/ molecular weight for pure

substances and morality based on titre value.

l Difference between precipitate and solution.

l Principles of formal group analysis.

l Chemical equilibrium, Le Chatelier's principle

l Electrolytic conductance, calculation of emf of the cell and cell representation, Nernst equation

l Ionic equilibria, calculation of pH value, solubility and solubility product

l Bronsted-Lowry's concept for acid and base Buffer action of basic buffer

l Preparation of inorganic compounds

l General electronic configuration of inner transition elements

l Conversion of organic compounds, balancing of equations and named organic reactions

l Chemical tests to distinguish between organic compounds



Examination Paper 2015

l Relative molecular mass and mole (numerical problems), abnormal molecular weights.

l Solid state, voids and defects in solid state.

l Ionic equilibria (numerical problems) concept of solubility product, ionic product and common ion effect.

l Electrolytic conductance, electrode potential and Nernst equation.

l Nomenclature, isomerism, hybridization and geometry of coordination

compounds.

l Balancing of equations for inorganic compounds.

l Organic conversions, named reactions and balancing of equations.

l Organic conversions and balanced equations

l Named organic reactions (Balz-Schiemann’s reaction)

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( 7 )

Examination Paper 2017

l Certain colours like buff precipitate

l Solubility of mixture or preparation of original solution for group separation

l Use of neutralized sodium carbonate extract for confirmatory test of anion

l Identification of gases

l Systematic analysis from group zero to IV and reporting absence and presence of groups

Examination Paper 2016

l Van't Hoff factor and molecular weight

l Anisotropic and isotropic

l Common ion effect and solubility product

l Total number of particles in bcc and fcc unit cell and their relationship

l Paramagnetic and diamagnetic

l Edge length (a) and radius (r) of various types of cubic unit cell and their

relationship

l Buffer action of acidic and basic buffer

l Concept of oxidation and reduction of SO2

l Gibb's free energy and emf of cell in terms of spontaneity

l Types of polymerization and polymer

Examination Paper 2015

l Vant Hoff factor, calculation of degree of dissociation.

l Azeotropic mixtures, ideal and non-ideal solutions.

l Order and molecularity of reaction, calculation of time period for the

st

decomposition of radioactive elements by 1 order kinetics.

l Le Chatelier’s principle, change in equilibrium with change in pressure and temperature.

l Van Hoff factor and colligative properties

l Raoult’s Law and elevation of boiling point

l Calculation of activation by using slope of the graph

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ð Read questions carefully and understand what is required before attempting the question

Practice numerical problems regularly, solve the numerical stepwise with correct

ð

formula and write the answer with correct unit

ð Learn complete and balanced equations along with the conditions, in inorganic and organic compounds

Avoid selective study

ð Learn the shapes and hybridization of molecules with diagram

While solving numerical problems, proper steps should be followed, i.e formula,

ð

substitution and correct answer with units

ð Avoid selective study, give equal importance to all the topics.

ð Practice more numerical problems Solve the problems step-wise with correct formula and units.

ð Learn both positive and negative chemical tests in organic reactions as it will help

in distinguishing between organic compounds.

ð Learn the reactions both organic and inorganic with proper conditions Always write the correct balanced equations.

ð Do not give dual statements for any answer.

Learn to write the key words in the answer.

ð

ð Numericals should be practiced regularly

Practice organic conversions with correct conditions Write the correct balanced

ð

chemical equations.

ð Read the question carefully and understand what is required before

attempting the answers.

ð Study chemical tests to distinguish between organic compounds.

ð Write the formula then substitute the values and calculate the answers

with correct units.

( 8 )

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( 9 )

LATEST SYLLABUS

CHEMISTRY

CLASS 12

There will be two papers in the subject

Paper I: Theory 3 hours 70 marks Paper II: Practical : 3 hours 20 marks

Practical File 3 marks

PAPER 1 (THEORY) - 70 Marks

There will be no overall choice in the paper Candidates will be required to answer all questions Internal choice will be available in two questions of 2 marks each, two questions of 3 marks each and all the three questions of 5 marks each.

11 Alcohols, Phenols and Ethers

12 Aldehydes, Ketones and Carboxylic Acids

13 Organic Compounds containing Nitrogen

Solids: their classification based on different binding

forces such as: ionic, covalent molecular; amorphous

and crystalline solids (difference), metals Type of

unit cell in two dimensional and three dimensional

lattices, number of atoms per unit cell (all types)

Calculation of density of unit cell, packing in solids,

packing efficiency, voids, point defects, electrical and

magnetic properties

Band theory of metals Conductors, semiconductors

(n and p type) and insulators.

(i) Crystalline and amorphous solids.

(ii) Definition of crystal lattice, unit cell; types of unit cell

(scc, fcc, bcc); calculation of the number of atoms per unit

cell; relationship between radius, edge length and nearest

neighbour distance Calculation of density of unit cell,

formula of the compound – numericals based on it; packing

in 3 – D, packing fraction in scc, fcc, bcc with derivation;

voids – types, location, formation (derivation of radius of

voids).

(iii) Characteristics of crystalline solids; ionic (NaCl), metallic

(Cu), atomic (diamond and graphite).

(iv) Point defects: Stoichiometric, nonstoichiometric and impurity defects (F- centres).

(v) Electrical properties: Conductors, semiconductors (n & p

types) and insulators (Band Theory), piezoelectricity and pyroelectricity.

(vi) Magnetic properties: diamagnetic, paramagnetic, ferromagnetic, ferrimagnetic and antiferromagnetic.

2 Solutions :

Study of concentration of solutions of solids in liquids, liquid in liquid, solubility of gases in liquids, solid solutions, Colligative properties Raoult's law

of relative lowering of vapour pressure (1st & 2nd), elevation of boiling point, depression of freezing point, osmotic pressure Use of colligative properties

in determining molecular masses of solutes, abnormal molecular mass association and dissociation, van't Hoff factor

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( 10 )

Normality, molality, molarity, mole fraction, ppm, as

measures of concentration Definition of the above with

examples Simple problems based on the above

(i) Solubility of gases in liquids – Henry’s Law, simple

numericals based on the above

(ii) Raoult’s Law for volatile solutes and nonvolatile

solutes, ideal solution, non-ideal solution Azeotropic

mixtures – definition, types, graphical representation,

fractional distillation with examples

(iii) Colligative properties – definition and examples, and

its use in determination of molecular mass.

(a) Relative lowering of vapour pressure:

Definition and mathematical expression of

Raoult’s Law Determination of relative

molecular mass by measurement of lowering of

vapour pressure

(b) Depression in freezing point: molal depression

constant (cryoscopic constant) – definition and

mathematical expression (derivation included)

(c) Elevation in boiling point method: molal

elevation constant (ebullioscopic constant)

definition and mathematical expression

(derivation included).

(d) Osmotic pressure: definition and explanation

Natural and chemical semipermeable membranes,

reverse osmosis, isotonic, hypotonic and

hypertonic solutions Comparison between

diffusion and osmosis Application of osmotic

pressure in the determination of relative

molecular mass

van’t Hoff- Boyle’s Law, van’t Hoff – Charles’

Law, van’t Hoff - Avogadro’s law

(e) Abnormal molecular mass: Dissociation and

Association with suitable examples

(f) van’t Hoff factor for the electrolytes which

dissociate and the molecules which associate

in solution Modification of the formula of

colligative properties based on van’t Hoff factor

Simple problems Calculation of degree of

dissociation and association Experimental

details not required.

Numerical problems based on all the above methods

Experimental details not required.

3 Electrochemistry

Electrolytic and electrochemical cells Redox reactions

in electrochemical cells Electromotive Force (emf) of

a cell, standard electrode potential, Nernst equation

and its application to chemical cells Relation between

Gibbs energy change and emf of a cell

Conductance in electrolytic solutions, specific,

equivalent and molar conductivity, variationsof

conductivity with concentration, graphs; Kohlrausch's

Law of electrolysis and Faraday’s Laws of electrolysis

Dry cell and lead accumulator, fuel cells,corrosion

(i) Electrochemical cells: introduction, redox reactions

(principle of oxidation and reduction in a cell) (ii) Galvanic cells - introduction; representation, principle

– oxidation reduction Mechanism of production of electric current in a galvanic cell

(iii) Measurement of potential Single electrode potentials

Standard hydrogen electrode (E°) - definition, preparation, application and limitations

Standard electrode potential - Measurement of

standard electrode potential of Zn ++ / Zn, Cu ++ / Cu, half cell (using standard hydrogen electrode)

Cell notation – representation

Factors affecting electrode potential with explanation

- main emphasis on the temperature, concentration and nature of the electrode

(iv) Electrochemical series Its explanation on the basis of

standard reduction potential Prediction of the feasibility of a reaction.

(v) Nernst equation and correlation with the free energy

of the reaction with suitable examples

Prediction of spontaneity of a reaction based on the

cell emf Numericals on standard electrode potential

of half-cells, cell emf, relationship between free energy and equilibrium constant, standard electrode potential and free energy

(vi) Comparison of metallic conductance and electrolytic

conductance Relationship between conductance and resistance Specific resistance and specific conductance Cell constant: Calculation of cell constant Meaning

of equivalent conductance Meaning of molar conductance General relationship between specific conductance, molar conductance and equivalent conductance (units and graphs) Units, numericals Molar conductance of a weak electrolyte at a given concentration and at infinite dilution Kohlrausch’s Law – definition, applications and numericals

(vii) Faraday’s laws of Electrolysis

Faraday’s First Law of electrolysis Statement,

mathematical form Simple problems

Faraday’s Second Law of electrolysis: Statement,

mathematical form Simple problems

Relation between Faraday, Avogadro’s number and charge on an electron F = N Ae should be given (no details of Millikan’s experiment are required)

(viii)Batteries: Primary and Secondary Cells: Leclanche

cell, mercury cell, Lead storage battery and fuel cell – structure, reactions and uses

(ix) Corrosion: Concept, mechanism of electrochemical

reaction, factors affecting it and its prevention.

4 Chemical Kinetics

Meaning of Chemical Kinetics – slow and fast reactions Rate of a reaction - average and instantaneous rate (graphical representation) Factors affecting rate of reaction: surface area, nature of reactants, concentration, temperature, catalyst and radiation Order and molecularity of a reaction, rate law and specific rate constant Integrated rate equations and

.contd.

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( 11 )

half-life (only for zero and first order reactions),

concept of collision theory (elementary idea, no

mathematical treatment) Concept of threshold and

activation energy, Arrhenious equation

(i) Meaning of chemical kinetics, Scope and importance

of Kinetics of the reaction, slow and fast reactions –

explanation in terms of bonds.

(ii) Rate of Reaction: definition, representation of rate of

reaction in terms of reactants and products,

determination of rate of reactions graphically,

instantaneous and average rate of reaction Factors

affecting rate of reaction.

(iii) Law of mass Action: statement and meaning of

active mass Explanation with an example – general

reactions

(iv) Effect of concentration of reactants on the rate of a

reaction: Qualitative treatment, based on the law

of mass Action, statement of rate law, General rate

equation – Rate = k(concentration of the reactant)

n, where k is rate constant and n is the order of the

reaction, relationship between the rate of the reaction

with rate constant with respect to various reactants.

(v) Order of a reaction: meaning, relation between order

and stoichiometric coefficients in balanced equations,

order as an experimental quantity, rate equation

for zero order reaction and its unit, mathematical

derivation of rate equation for first order reaction,

characteristics of first order reaction – rate constant

is independent of the initial concentration, units to

be derived, definition of half-life period, derivation

of expression of half-life period from first order rate

equation.

Problems based on first order rate equation and

half-life period

(vi) Molecularity of the reaction: Meaning – physical

picture, Relation between order, molecularity and

the rate of a reaction, Differences between order and

molecularity of a reaction.

(vii) The concept of energy: Exothermic and endothermic

reactions, concept of energy barrier, threshold and

activation energy, formation of activated complex,

effect of catalyst on activation energy and reaction

rate

(viii) Collision Theory: Condition for a chemical change

– close contact, particles should collide Collisions to

be effective – optimum energy and proper orientation

during collision Energy barrier built-up when the

collision is about to take place, Activated complex

formation, difference in energy of the reactant and the

product – exothermic and endothermic reactions with

proper graphs and labelling

(ix) Mechanism of the reaction: meaning of elementary

reaction, meaning of complex and overall reaction,

explanation of the mechanism of the reaction, slowest

step of the reaction Relationship between the rate

expression, order of reactants and products at the

rate-determining step, units of rate constant – explanation

with suitable examples

(x) Effect of temperature on the rate constant of a

reaction: Arrhenius equation – K=Ae -Ea/RT , Meaning

of the symbols of Arrhenius equation, related graph, evaluation of Ea and A from the graph, meaning of slope of the graph, conversion from exponential to log form of the equation, relationship between the increase in temperature and the number of collisions Numerical based on Arrhenius equation.

Colloidal state distinction between true solutions, colloids and suspension; lyophilic, lyophobic multi-molecular, macromolecular and associated colloids; properties of colloids; Brownian movement, Tyndall effect, coagulation and electrophoresis Emulsion - types ofemulsions

(i) Difference between absorption and adsorption: definition of physisorption and chemisorption and their differences.

Factors affecting adsorption of gases on solids, Freundlich adsorption isotherms, graph, expression and application of adsorption

(ii) Catalysis: definition, types of catalysts – positive and

negative, homogeneous and heterogeneous catalyst based on the state of the reactant and the catalyst, Elementary treatment of intermediate compound formation theory with examples; adsorption Theory, effect of catalyst on the rate of reaction – the change

in the energy of activation in the activation energy curve Characteristics of a catalyst; specificity, activity, surface area of a catalyst Promoter and poison Enzyme catalysis – basic idea and lock and key mechanism

(iii) Colloidal State: Thomas Graham classified the

substances as crystalloid and colloid, classification

of substances on the basis of the particle size i.e true solution, sol and suspension, colloidal system

is heterogeneous lyophilic and lyophobic colloid;, classification of colloidal solutions as micro, macro and associated colloids

Preparation of lyophilic colloids Preparation of lyophobic colloids by colloid mill, peptization, Bredig’s arc method, oxidation, reduction, double decomposition and exchange of solvent method, purification of colloids (dialysis, ultra-filtration, and ultracentrifugation)

Properties of colloidal solutions:Brownian movement, Tyndall effect, coagulation, electrophoresis (movement

of dispersed phase), Protection of colloids, Gold number and Hardy- Schulze rule Emulsions, surfactants, micelles (only definition and examples)

Application of colloids and emulsions in daily life.

contd.

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( 12 )

6 General Principles and Processes of Isolation of

Elements

Metals: metallurgy, ores, principles and methods

of extraction - concentration, oxidation, reduction,

electrolytic refining Occurrence and principles of

extraction of aluminium, copper, zinc, iron and silver

(i) Definition of minerals, ores and metallurgy; principle

ores of aluminium, iron, copper, zinc and silver.

Methods of concentration of ores: hydraulic washing,

magnetic separation, froth floatation method, leaching

Extraction of metal from concentrated ore – calcination,

roasting and thermal reduction.

Thermodynamic principle of metallurgy Gibb’s energy

(Ellingham diagram – significance only).

Metallurgy of aluminium, iron, copper, zinc and

silver.

Refining of metals - distillation, liquation, electrolysis,

vapour phase refining (nickel), zone refining.

(ii) Uses of metals and their alloys.

7 p-Block Elements

Group-15 Elements

Position in the periodic table, occurrence, electronic

configuration, oxidation states, trends in physical

and chemical properties Nitrogen: preparation

properties and its uses; compounds of nitrogen:

oxides of nitrogen Ammonia and nitric acid –

preparation and properties Phosphorus - allotropic

forms, compounds of phosphorus: preparation and

properties of phosphine, halides and oxoacids

(i) General introduction, electronic configuration,

occurrence, oxidation states Trends in physical

properties; chemical properties with hydrogen, oxygen

and halogens

(ii) Nitrogen - Laboratory preparation, decomposition

(ammonium dichromate, barium azide) Properties

and uses

(iii) Oxides of nitrogen (N 2 O, NO, N 2 O 3 , N 2 O 4 , N 2 O 5 ) -

preparation, structure and uses

(iv) Ammonia – Preparation and manufacture Properties:

reaction with oxygen, copper oxide, chlorine,

hydrochloric acid, formation of complexes Uses

(v) Nitric Acid - Preparation and manufacture Properties:

reaction with copper (dilute and concentrated HNO 3 ),

carbon and sulphur Uses.

(vi) Allotropes of phosphorus and their structures

Phosphine – preparation from phosphorus and

properties: reaction with halo acids) Phosphorus

trichloride - Preparation from phosphorous Uses

Phosphorus pentachloride - preparation from PCl 3

Thermal dissociation and hydrolysis Uses, properties.

Oxoacids of phosphorus (structures and preparation only)

Position in the periodic table, occurrence, electronic

configuration, oxidation states, trends in physical

and chemical properties Oxygen: methods of

preparation, properties and uses, classification of

oxides Ozone – methods of preparation Sulphur

-allotropic forms Compounds of sulphur:

preparation, properties and uses of sulphur-dioxide, sulphuric acid (industrial process of manufacture) Oxoacids of sulphur (structures only)

(i) Electronic configuration, oxidation states, occurrence

Trends in physical properties; chemical properties with hydrogen, oxygen and halogens

(ii) Oxygen – lab method of preparation, formation of

oxides with metals and nonmetals and their common nature

(iii) Ozone: manufacture by Siemen’s ozoniser, thermal

decomposition of ozone, its oxidising nature – reaction with lead sulphide, potassium iodide and mercury, its uses

(iv) Sulphur: allotropes of sulphur rhombic, monoclinic,

structure of sulphur and action of heat; extraction by Frasch process

(v) Sulphur dioxide: laboratory and industrial preparation from sulphites and sulphide ores, reaction of sulphur dioxide with NaOH, Cl 2 , KMnO 4 and structure of

SO 2 (vi) Oxoacids of sulphur: structures only.

Sulphuric Acid: manufacture by Contact Process

(equations, conditions and diagram), properties - acidic nature, mode of dilution, oxidising action, dehydrating nature and uses of sulphuric acid in industry

Group-17 Elements

Position in the periodic table, occurrence, electronic configuration, oxidation states, trends in physical and chemical properties; Preparation, properties and uses of chlorine and hydrochloric acid Compound

of halogen, oxoacids of halogens (structures only), Interhalogen compounds

(i) General introduction, electronic configuration,

oxidation states Trends in physical properties and chemical properties (hydrogen, oxygen, halogens and metals)

(ii) Chlorine – preparation from MnO 2 and HCl, from

NaCl, MnO 2 and conc H 2 SO 4 (only equations), reactions of chlorine with H 2 S, NH 3 , cold, dilute NaOH and hot, concentrated NaOH

(iii) Hydrochloric acid: Lab preparation, its acidic nature,

reaction with ammonia, carbonates and sulphites, formation of aqua regia and its uses

(iv) Oxoacids of halogens: structures and acidic property (v) Interhalogen compounds – structure, hybridisation

and shapes: XX’, XX’ 3 , XX’ 5 , XX’ 7

Position in the periodic table, occurrence, electronic configuration, trends in physical and chemical properties, inert nature, uses

(i) General introduction, electronic configuration,

occurrence, trends in physical; chemical properties, state and low reactivity

(ii) Formation of xenon compounds with fluorine and

oxygen (equations only), hybridisation, shape and structure of compounds

(iii) Uses of noble gases.

contd.

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( 13 )

8 d and f Block Elements

Position in the periodic table, occurrence, electronic

configuration and characteristics of transition

metals, general trends in properties of the 3d-series

of transition metals - metallic character, ionisation

enthalpy, oxidation states, ionic radii, colour of ions,

catalytic property, magnetic properties, interstitial

compounds, alloy formation, preparation and

properties of K2Cr2O7 and KMnO4

Lanthanoids and actinoids

(i) d-Block: 3d, 4d and 5d series

Study in terms of metallic character, atomic and ionic

radii, ionisation enthalpy, oxidisation states, variable

valency, formation of coloured compounds, formation

of complexes, alloy formation.

(ii) f-Block: 4f and 5f series

Electronic configuration, atomic and ionic radii,

oxidisation states, formation of coloured compounds,

formation of complexes, alloy formation Lanthanoid

contraction and its consequences Chemical reactivity

– with oxygen, hydrogen, halogen, sulphur, nitrogen,

carbon and water.

Actinoids - oxidation states and comparison with

lanthanoids.

(iii) Potassium permanganate: structure, shape, equation

of extraction from pyrolusite ore, its oxidising nature

in acidic, basic and neutral medium, use in redox

titration.

Oxidising nature in acidic [FeSO 4 , (COOH) 2 2H 2 O,

KI], basic (KI) and neutral (H 2 S) mediums to be done.

(iv) Potassium dichromate: structure, shape, equation of

extraction from chromite ore and its use in titration

Oxidising nature in acidic, basic and neutral medium,

use in redox titration Interconversion of chromate

and dichromate ion (effect of pH).

9 Coordination Compounds

Concept of complexes, definition of ligands,

coordination number, oxidation number IUPAC

nomenclature of mononuclear coordination

compounds Isomerism (structural and stereo)

Bonding, Werner's theory, VBT and CFT

Colour, magnetic properties and shapes Importance

of coordination compounds (in qualitative analysis,

extraction of metals and biologicalsystem)

(i) Definition of coordination compounds / complex

compounds, differences with a double salt, study

of ligands – mono-, bi-, tri, tetra-, penta-, hexa-

and polydentate, chelating ligands, definition of

coordination number, its calculation for a complex

coordination sphere, study of oxidation state of an

element in a complex, its calculation, IUPAC rules of

nomenclature of coordination compounds

(ii) Isomerism – structural, stereo types and examples

(iii) Valence bond theory of coordination compounds –

examples of formation of inner orbital and outer orbital

complexes (high and low spin, octahedral, tetrahedral

and square planar), prediction of magnetic character

(iv) Crystal field theory – crystal field splitting in tetra

and octahedral systems Explanation of colour and magnetic character

(v) Stability of coordination compounds (explain stability

on the basis of magnitude of K) as mentioned above) (vi) Importance and uses.

10 Haloalkanes andHaloarenes.

Haloalkanes: General formula, nomenclature and

classification Nature of C–X bond, physical and chemical properties, mechanism of substitution reactions, opticalrotation

Haloarenes: Basic idea, nature of C–X bond,

substitution reactions (directive influence of halogen

in monosubstituted compoundsonly)

Uses and environmental effects of dichloromethane, trichloromethane, tetrachloromethane, iodoform, freons and DDT

Nature of C-X bond Naming the halogen derivatives of alkanes by using common system and IUPAC system for mono, di and tri- halo derivatives

Preparation of haloalkanes from:

- Alkane and halogen.

- Alkene and hydrogen halide.

- Alcohols with PX 3 , PCl 5 and SOCl 2

- Halide exchange method (Finkelstein and Swarts) -

- Silver salt of fatty acids (Hunsdiecker)

Physical properties: State, melting point, boiling point and solubility

Chemical properties: nucleophilic substitution reactions (S N 1, S N 2 mechanism in terms of primary, secondary and tertiary halides) Reaction with: sodium hydroxide, water, sodium iodide, ammonia, primary amine, secondary amine, potassium cyanide, silver cyanide, potassium nitrite, silver nitrite, silver salt of fatty acid and lithium-aluminium hydride

Elimination reaction (Saytzeff’s rule) / b elimination

Reaction with metals: sodium and magnesium (Wurtz’s reaction, Grignard’s reagent preparation) Chloroform and iodoform: preparation and properties

Structure of freons

Preparation of haloarenes by Sandmeyer’s and Gattermann’s reaction, by electrophilic substitution Physical properties: State, melting point, boiling point and solubility

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11 Alcohols, Phenols and Ethers

Alcohols: Classification, general formula, structure

and nomenclature Methods of preparation, physical

and chemical properties (of primary alcohols only),

identification of primary, secondary and tertiary

alcohols, mechanism of dehydration, uses with

special reference to methanol andethanol

(i) Classification into monohydric, dihydric and

polyhydric alcohols, general formulae, structure and

nomenclature of alcohols Difference between primary,

secondary and tertiary alcohols in terms of structure,

physical properties and chemical properties

(ii) Methods of preparation:

- Hydration of Alkenes – direct hydration, indirect

hydration, hydroboration oxidation

- From Grignard’s reagent

- Hydrolysis of alkyl halides

- Reduction of carbonyl compounds

- From primary amines

Manufacture of methanol by Bosch process and ethanol

by fermentation of carbohydrates, chemical equations

required (only outline of the method of manufacture, detail

not required)

Properties:

- Acidic nature of alcohols:

- Reaction with sodium

- Esterification with mechanism

- Reaction with hydrogen halides

- Reaction with PCl 3 , PCl 5 , and SOCl 2

- Reaction with acid chlorides and acid anhydrides -

Oxidation

- Dehydration with mechanism

Uses of alcohols

(iii) Conversion of one alcohol into another.

(iv) Distinction between primary, secondary and tertiary

alcohols by Lucas’ Test

Phenols : Classification and nomenclature Methods

of preparation, physical and chemical properties, acidic

nature of phenol, electrophilic substitution reactions, uses

of phenols

Preparation of phenol from diazonium salt, chlorobenzene

(Dow’s process) and from benzene sulphonic acid

Manufacture from Cumene

Physical properties: state and solubility.

Chemical properties:

- Acidic character of phenol

- Reaction with sodium hydroxide

- Reaction with sodium

- Reaction with zinc

- Reaction with acetyl chloride and acetic anhydride

- Reaction with phosphorus penta chloride -

Bromination, nitration and sulphonation (Electrophilic

substitution reactions)

- Kolbe’s reaction (formation of salicylic acid)

- Reimer – Tiemann reaction

- Test for phenol – FeCl 3 test, azo dye test.

Aliphatic Ethers : General formula, structure and nomenclature Methods of preparation, physical and chemical properties, uses

Ethers: structure of ethereal group

Preparation from alcohol (Williamson’s synthesis) Physical properties: state, miscibility

Chemical properties:

- Reaction with chlorine

- Oxidation (peroxide formation)

- Reaction with HI

- Reaction with PCl 5

Aryl ethers

Physical properties – state and solubility

Chemical properties – preparation of anisole (Williamson’s synthesis), electrophilic substitution (halogenation, nitration and Friedel-Crafts reaction.) Uses of ether.

12 Aldehydes, Ketones and CarboxylicAcids

Aldehydes and Ketones : Nomenclature, structure

of methods of preparation of aldehydes and ketones, physical and chemical properties, mechanism of nucleophilic addition, reactivity of alpha hydrogen

in aldehydes and uses

Preparation:

l From alcohol

l From alkenes (ozonolysis).

l From alkynes (hydration)

l From acid chlorides (Rosenmund’s reduction, reaction

with dialkyl cadmium)

l From calcium salt of carboxylic acids

l From nitriles (Stephen reaction, Grignard’s reagent)

l From esters Physical properties – state and boiling

point Chemical properties:

l Nucleophilic addition reactions with mechanism

(ammonia and its derivatives, HCN, NaHSO 3 and Grignard’s reagent)

l Oxidation reactions, iodoform reaction

l Reduction: reduction to alcohol and alkanes

(Clemmensen’s reduction, Wolff-Kishner reduction, Red phosphorus and HI)

l Base catalysed reactions (with mechanism): Aldol

condensation, cross Aldol condensation, Cannizzaro’s reaction.

Tests: difference between formaldehyde and acetaldehyde; aldehydes and ketones.

Uses of aldehydes and ketones.

Aromatic aldehyde (Benzaldehyde)

Lab preparation from toluene by oxidation with chromyl chloride

Physical properties: state and stability

Chemical properties:

l Oxidation and reduction

l Nucleophilic addition reaction (hydrogen cyanide and

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Carboxylic Acids : Classification, general formula

and structure of carboxylic group Nomenclature,

acidic nature, methods of preparation, physical and

chemical properties and uses

Classification of mono and di carboxylic acids with

examples

Preparation of aliphatic and aromatic carboxylic acid:

- From alcohols, aldehydes

- From nitriles

- From Grignard’s reagent

Physical properties: state, boiling point and solubility.

Chemical properties:

- Acidic character: (aliphatic, aromatic carboxylic acids

with the effect of substituents on the acidic character –

to be dealt with in detail)

- Reaction with active metals, alkalies, carbonates and

bicarbonates,

- Formation of acid derivatives

- Decarboxylation (chemical and Kolbe’s electrolytic

reaction).

- HVZ reactions.

- Substitution of benzene ring (meta directive effect

of carboxylic acid group) nitration and sulphonation.

Tests for acids: formic acid, acetic acid and benzoic acid.

Uses of formic acid, acetic acid and benzoic acid.

13 Organic compounds containing Nitrogen

Aliphatic Amines : General formula and,

classification of amines Structure of the amino group,

nomenclature Methods of preparation, physical and

chemical properties, uses, identification of primary,

secondary and tertiary amines

- From amide (Hofmann’s degradation).

- From nitro compounds.

- Gabriel phthalimide Synthesis.

Physical properties: comparison between primary,

secondary and tertiary amines in terms of – state,

solubility, boiling point (hydrogen bonding), comparison

with alcohols

Chemical properties :

- Basic character of amines – comparison between primary, secondary and tertiary alkyl amines/ ammonia/ aniline Effect of substituents on the basic strength of aniline

- Alkylation and acylation with mechanism

- Reaction with nitrous acid

- Carbylamine reaction

Distinction between primary, secondary and tertiary amines (Hinsberg’s Test)

Aniline

Preparation reduction of nitrobenzene

Physical properties – state, solubility and boiling point Chemical properties:

- Reaction with HCl and H 2 SO 4

- From alkyl halide.

From primary amines

Diazonium salts : Preparation, chemical reactions and importance in synthetic organic chemistry

Preparation from aniline;

Properties: Sandmeyer’s reaction, Gattermann reaction and Balz – Scheimann reaction, replacement of diazo group

by – H, -OH, -NO 2 , coupling reaction with phenol and aniline.

14 Biomolecules Carbohydrates – Definition, Classification (aldoses and ketoses), monosaccahrides (glucose and fructose), D-L configuration oligosaccharides (sucrose, lactose, maltose), polysaccharides (starch, cellulose, glycogen); Importance of carbohydrates Carbohydrates: definition, classification - mono (aldose, ketose), oligo (di, tri, tetra saccharides) and polysaccharides with examples: reducing sugars and non reducing sugars – examples and uses.

Establishment of structures for glucose and fructose (open and cyclic) heating with HI, reaction with hydroxylamine, bromine water, acetic anhydride, nitric acid and phenyl hydrazine

Test for glucose and fructose (bromine water test with equation)

contd.

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( 16 )

Disaccharides – structures of sucrose, maltose and lactose

(glycosidic linkage)

Polysaccharides – starch, cellulose, glycogen

Proteins – structural units of proteins Basic idea of

- amino acids, peptide bond, polypeptides, proteins,

structure of proteins primary, secondary, tertiary

structure and quaternary structures (qualitative idea

only), denaturation of proteins Enzymes, hormones

elementary idea only

Proteins: Amino acids – general structure, classification

and zwitter ion formation Isoelectric point

Classification of proteins on the basis of molecular shape;

primary, secondary, tertiary and quaternary, structures

of proteins, denaturation of proteins (Definitions only

Details and diagrams are not required).

Vitamins - Classification andfunctions

Vitamins A, B, C, D, E and K: classification (fat soluble

and water soluble), deficiency diseases (Chemical names

and structures are not required).

Nucleic Acids - DNA and RNA

Nucleic acids: basic unit – purine and pyrimidine, DNA

– structure (double helical), RNA (No chemical structure

required) Differences between DNA and RNA.

15 Polymers

Definition and classification on different

parameters Methods of polymerisation (addition

and condensation), copolymerisation, and some

important polymers: natural and synthetic like

polythene, nylon polyesters, bakelite, rubber

Biodegradable and nonbiodegradable polymers

Classification based on source, on structure, on mode of

polymerisation, on molecular forces, on growth (with free radical mechanism) Preparation of important addition polymers Polythene, polypropene, PVC, PTFE, polystyrene Rubber – natural and synthetic (Buna-N and Buna-S), vulcanisation of rubber

Preparation of important condensation polymers - polyester, Nylon 66, Nylon 6, Bakelite, melamine (to be learnt in terms of monomers and equations) Biodegradable polymers – PHBV, Nylon 2 - Nylon 6 Uses.

16 Chemistry in Everyday life

Chemicals in medicines - analgesics, tranquilizers antiseptics, disinfectants, antimicrobials, antifertility drugs, antibiotics, antacids,antihistamines

In medicine: antipyretics, analgesics, tranquillisers, antiseptics, disinfectants, anti-microbials, anti-fertility drugs, antihistamines, antibiotics, antacids Definition, common examples, uses

Differences between antiseptics and disinfectants Structure not required

Chemicals in food - preservatives, artificial sweetening agents, elementary idea of antioxidants

Preservatives: role, example (Sodium benzoate) Artificial sweetening agents: role, examples (aspartame, saccharine, sucralose and alitame)

Soaps and detergents - Classification and their cleansing action

Soaps and detergents: classification, structure and some important examples

Advantage of detergents over soaps; classification of detergents into anionic/biodegradable, cationic/non biodegradable and non-ionic.

.contd.

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ISC Solved Paper, 2018

Class-XII

Chemistry

(Maximum Marks : 70) (Time allowed : Three hours)

(Candidates are allowed additional 15 minutes for only reading the paper.

They must NOT start writing during this time.)

All questions are compulsory Question 1 is of 20 marks having four sub parts, all of which are compulsory Question numbers 2 to 8 carry 2 marks each,

with any two questions having internal choice.

Question numbers 9 to 15 carry 3 marks each, with any two questions having an internal choice.

Question numbers 16 to 18 carry 5 marks each, with an internal choice.

All working, including rough work, should be done on the same sheet as, and adjacent to

the rest of the answer.

The intended marks for questions or parts of questions are given in brackets [J.

Balanced equations must be given wherever possible and diagrams where they are helpful.

When solving numerical problems, all essential working must be shown.

In working out problems, use the following data:.

Gas constant R = 1.987 cal deg –1 mol –1 = 8.314 JK -1 mol –1 = 0.0821 dm 3 atm 11 atm = / dm 3 atm = 101.3 J.

1 Faraday = 96500 coulombs Avogadro’s number = 6.023 × 10 23

Question 1

(a) Fill in the blanks by choosing the appropriate word/words from those given in the brackets : [4 × 1] (square pyramidal, electrical, 74, 26, sp3d2, sp3d, chemical, 68, 32, tetrahedral, yellow, white, iodoform, Lucas)

(i) A Galvanic cell converts energy into _ energy.

(ii) The percentage of unoccupied spaces in bcc and fcc arrangements are and _, respectively.

(iii) Propan-2-ol on reaction with iodine and sodium hydroxide gives precipitate and the reaction is called

test

(iv) The geometry of XeQF4 molecule is _ and the hybridisation of xenon atom in the molecule is _

(b) Complete the following statements by selecting the correct alternative from the choices given : [4 × 1] (i) During the course of an sn! reaction, the intermediate species formed is :

(ii) Purification of aluminium by electrolytic refining is called :

(iii) An aqueous solution of urea freezes at –0.186°C, Kf for water = 1.86 K kg mol–1, Kb for water = 0.512 K kg

mol–1 The boiling point of urea solution will be :

(iv) In the dehydration of alcohols to alkenes by heating with concentrated sulphuric acid, the initiation step is :

(1) formation of carbocation (2) formation of an ester

(3) protonation of alcohol molecule (4) elimination of water

(i) (1) Why does the density of transition elements increase from Titanium to Copper ?

(at, no Ti = 22, Cu = 29)

(2) Why is zinc not regarded as a transition element ?

(at, no Zn = 30)

Trang 19

(ii) Identify the compounds A, B, C and D.

CH3CN H O H2 / +

 A → NH B 3→  →heat C Br KOH D2 / →

(iii) Calculate the osmotic pressure of a solution prepared by dissolving 0.025g of K2SO4 in 2.0 litres of water at

25°C assuming that K2SO4 is completely dissociated, (mol, wt of K2SO4 = 174 g mol–1)

(iv) What type of isomerism is shown by the following coordination compounds :

[Pt Cl2 (NH3)4] Br2 and [Pt Br2(NH3)4]Cl2

Write their 1UPAC names

(a) (i) Write the rate law expression for the reaction A + B + C → D + E , if the order of reaction is first, second and

zero with respect to A, B and C, respectively

(ii) How many times the rate of reaction will increase if the concentration of A, B and C are doubled in the

equation given in (i) above?

OR (b) The rate of reaction becomes four times when the temperature changes from 293 K to 313 K Calculate the energy

of activation (Ea) of the reaction assuming that it does not change with temperature (R = 8.314 K–1 mol–1)

(a) How do antiseptics differ from disinfectants?

(b) State the role of the following chemicals in the food industry :

An aromatic organic compound [A] on heating with NH3 and Cu2O at high pressure gives [B| The compound [B]

on treatment with ice cold solution of NaNO2 and HCl gives [C], which on heating with Cu/HCI gives compound [A] again Identify the compounds [A], [BJ and [C] Write the name of the reaction for the conversion of (B] to [C]

(a) How will you obtain the following? (Give balanced equation.)

(i) Picric acid from phenol.

(ii) Ethyl chloride from diethyl ether.

OR (b) How will you obtain the following? (Give balanced equation.)

(i) Anisole from phenol

(ii) Ethyl acetate from ethanol

40% of a first order reaction is completed in 50 minutes How much time will it take for the completion of 80% of this reaction?

(a) The freezing point of a solution containing 5.85g of NaCl in 100g of water is – 3.348°C Calculate van’t Hoff factor

’i’ for this solution What will be the experimental molecular weight of NaCl?

(Kf for water = l.86 K kg mol –1, at wt Na = 23, Cl = 35.5)

OR (b) An aqueous solution containing 12.48 g of barium chloride (BaCl2) in 1000g of water, boils at 100.0832°C Calculate the degree of dissociation of barium chloride, (Kb for water = 0.52 K kg mol–1, at wt Ba = 137, Cl = 35.5)

Give reason for each of the following :

(a) For ferric hydroxide sol the coagulating power of phosphate ion is more than chloride ion

(b) Medicines are more effective in their colloidal form.

(c) Gelatin is added to ice creams.

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SOLVED PAPER - 2018| 19

(a) For the complex-ion [Fe(CN)6J3–, state :

(i) the type of hybridisation.

(ii) the magnetic behaviour.

(iii) the oxidation number of the central metal atom.

(b) Write the IUPAC name of [Co(en)2Cl2]+ ion and draw the structures of its geometrical burners

(a) Explain why :

(i) Mn2+ is more stable than Fe2+ towards oxidation to +3 state

(At no of Mn-25, Fe-26)

(ii) Transition elements usually form coloured ions.

(iii) Zr and Hf exhibit similar properties.

(At no of Zr = 40, Hf=72)

OR (b) Complete and balance-the following chemical equations :

(b) Give a balanced chemical equation to convert methyl cyanide to ethyl alcohol,

(c) What happens when benzene diazonium chloride reacts with phenol in weak alkaline medium?

(Give balanced equation)

Given E°Zn2+/Zn = – 0.763 and E°Cd2+/Cd = – 0.403V

(ii) Define the following terms :

OR (b) (i) The specific conductivity of a solution containing 5 g of anhydrous BaCl2 (mol wt = 208) in 1000 cm3 of a

solution is found to be 0.0058 ohm–1 cm−1 Calculate the molar and equivalent conductivity of the solution

(ii) What is an electrochemical series? How is it useful in predicting whether a metal can liberate hydrogen from

acid or not?

(a) (i) Explain why :

(1) Nitrogen does not form pentahalides (2) Helium is used for filling weather balloons

(3) ICl is more reactive than I2

(ii) Draw the structures of the following :

OR (b) (i) Explain why :

(1) Mercury loses its meniscus in contact with ozone.

(2) Halogens are coloured and the colour deepens on moving down in the group from fluorine to iodine (3) Hydride of sulphur is a gas while hydride of oxygen is a liquid.

(ii) Complete and balance the following reactions :

(1) NaCl + MnO2 + H2SO4 → + + +

(2) KMnO4 + SO2 + H2O → + +

(a) (i) Give balanced equations for the following reactions :

(1) Benzaldehyde reacts with hydrazine.

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(2) Acetic acid reacts with phosphorous pentachloride.

(3) Acetone reacts with sodium bisulphite.

(ii) Give one chemical test each to distinguish between the following pairs of compounds :

(1) Ethanol and acetic acid

(2) Acetaldehyde and benzaldehyde

OR (b) (i) Write chemical equations to illustrate the following name reactions :

(ii) Explain why :

(1) Acetaldehyde undergoes aldol condensation, but formaldehyde does not.

(2) Acetic acid is a weaker acid as compared to formic acid.



SOLUTIONS

(iii) yellow and Iodoform (iv) square pyramidal and sp3d 2

(c) (i) Rate constant → Arrhenius equation (ii) Biodegradable polymer → PHBV.

(iii) Zwitter ion → Glycine (iv) Purification of colloids → Dialysis.

(d) (i) (1) In transition elements the electrons are being added to the inner shells (d or f sub-shells) where they

are very effective at screening the outer electrons from the nuclear charge This trend in density can

be explained by the small and irregular decrease in metallic radii coupled with the relative increase

in atomic mass

(2) Zinc is not a transition metal because its stable ion Zn2+ has completely filled d-orbitals Transition

metals are compounds that form at least one stable ion with incomplete d-structure.

The electronic configuration of Zn and Zn2+ is [Ar] 3d10 4s2 and [Ar] 3d10, respectively

(ii) CH3CN H O H CH2 / +→ 3COOH NH CH3→ 3CONH2  →∆ CH3N=C=O Br KOH CH2 / → 3NH2

(iii) Osmotic pressure can be calculated as π = mRT

MV

( ), where m is the mass of the compound, R is the Gas

constant, T is the temperature, and V is the volume m = 0.025 gm, R = 8.31 J K−1 mol−1, T = 25° C or 298

K, M = 174 gm mol−1, and V = 2 L or 2000 × 10−6 m3

Thus, π = 177.9 N m−2, or π = 1779 dyne cm−2, or π = 1779 Pa

(iv) They will exhibit geometric isomerism (cis-and trans-)

The IUPAC names of [PtCl2(NH3)4] Br2 and [PtBr2(NH3)4] Cl2 are Tetraamminedichloroplatinum (IV)

bromide and Tetraamminedibromoplatinum (IV)chloride, respectively

[PtCl2(NH3)4] Br2 shows geometrical isomerism :

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3 (a) Antiseptics are applied to living skin or tissue to prevent infection whereas disinfectants are applied to

surfaces, equipments or other non-living things Both eliminate disease causing organisms

(b) (i) Sodium benzoate is the sodium salt of benzoic acid It is used as a preservative in the food industry and

can be found in acidic foods such as salad dressings, carbonated drinks (as carbonic acid), sauces and juices (citric acid), and pickles (acetic acid)

(ii) Aspartame is used as an intense sweetener in the food industry It is approximately 200 times sweeter

than sugar and is used in soft drinks, low calorie sugar free foods

Benzylchloride Benzylamine azo Compound Benzylchloride

5 (a) The monomer of Bakelite (C6H6O.CH2O) is Phenol and Formaldehyde

(b) The monomer of nylon-2-nylon is Glycine and Aminocaproic acid.

6 RNA : Purine base–Adenine and Guanine, Pyrimidine base–Uracil, Cytosine.

DNA : Purine base–Adenine and Guanine, Pyrimidine base–Thymine and Cytosine.

7 (a) (i) Picric acid from phenol

OH

298 3

Phenol 2, 4, 6 - trinitrophenol water

(ii) CH3CH2OCH2CH3 + PCl5  →∆ 2 CH3CH2Cl + POCl3

(b) (i) Anisole from phenol

Phenol Sodium Phenoxide Anisole Sodium bromide

(ii) Ethylacetate from ethanol

C2H5OH + CH3COOH → CH3COOC2H5 + H2O

Ethanol Acetic acid Ethylaetate Water

8 40% of first order reaction is completed in 50 min t = 2 when 80% is complete k = 2 303. log

Trang 23

(Molecular weight of solute × mass of solvent) Mass of solute= 5.85 g, Molecular weight of NaCl is 58.5 gm mol−1 (23 + 35.5), and mass of solvent is 100 g or 0.1 kg Thus, m = ( 58 5 0 15 85.× ), or m = 1 mol kg−1 Using the

above values, van’t Hoff factor i = 1.8.

(b) Change in the boiling point ∆Tb = 100.0832 − 100ºC, or ∆Tb = 0.0832°C, or ∆Tb = 0.0832 K The van’t Hoff

factor i is calculated as i = DT

Kb m b

( ), where K b = 0.52 K kg mol−1, molality m is calculated as m =Mass of solute/

(Molecular weight of solute × mass of solvent) Mass of solute= 12.48 g, Molecular weight of BaCl2 is 208 gm mol−1 (137 + 2×35.5), and mass of solvent is 1000 g or 1 kg Thus, m = 12.48/(208 × 1) Using the above values, van’t Hoff factor i = 2.67.

The degree of dissociation a is related to the van't Hoff factor i, as i = 1 + a (n – 1), or a = ( )

( )

i n

10 The given defect is stoichiometric As this defect arises because constituent particles are missing, it decreases the

density of the ionic compound This defect is known as Schottky defect, since the number of missing cations is equal to the number of missing anions

11 (a) The higher the valency of an active ion, higher is the coagulating power and lower is the coagulating value

Fe(OH)3 is positively charged, and PO34− has a higher valency than Cl−

(b) Medicines are more effective in their colloidal form as they can be easily absorbed by the tissues in the body (c) Gelatin is added to ice cream to give it a soft texture and fresh appearance It absorbs free water and prevents

the formation of large crystals and gives a less watery taste

12 (a) (i) The hybridisation of [Fe(CN6)]3 – is d2sp3

(ii) The magnetic behaviour is paramagnetic with an octahedral geometry and one electron.

(iii) The oxidation number of the central metal atom Fe= +3.

(b) Cis and Trans isomers of Dichlorobis ethylenediamine cobalt (III) chloride.

H2N

The IUPAC name of [Co(en)2Cl2]+ ion is Dichlorobis (ethylenediamine) Cobalt (III) Chloride

13 (a) (i) The electronic configuration of Mn2+ and Fe2+ are [Ar]183d5 and [Ar]183d6, respectively Mn2+ has a

stable state 3d5 configuration and is thus resistant towards oxidation to Mn3+ On the other hand, Fe2+has a 3d6 configuration and by losing one electron, it can change to a more stable 3d5 configuration Therefore, Fe2+ is easily oxidised to Fe3+ oxidation state

(ii) Transition metals have partially filled d-orbitals When they start bonding with other ligands, the

d-orbitals split and become non-degenerate which means they have different energy levels.

The electrons are able to absorb certain wavelengths of electromagnetic radiation to get to higher energy

level orbitals and during the downward transition emit light which gives them a coloured appearance

(iii) Zr and Hf exhibit similar properties due to lanthanide contraction Electrons present in the f-subshell are

not too effective in shielding, due to which the size gets constricted with atomic number and so the size

of Zr and Hf have nearly the same size and properties

(b) (i) 2 KMnO4 + 10 KI + 8 H2SO4 → 5 I2 + 2 MnSO4 + 6 K2SO4 + 8 H2O

(ii) K2Cr2O7 + 4 H2SO4 + 3 H2S → K2SO4 + Cr2(SO4)3 + 3 S + 7 H2O

(iii) 2 KMnO4 + 8 H2SO4 + 10 FeSO4 → 5 Fe2(SO4)3 + 2 MnSO4 + K2SO4 + 8 H2O

14 (a) C6H5NH2 < C2H5NH2 < (C2H5)2NH

C6H5NH2 will be least basic because of the de-localisation of the lone pair of electron present on the N-atom

over the benzene ring due to the −R effect of the C6H5 group On the other hand, the alkyl group C2H5 will tend to increase the electron density on the N-atom making it more easily available for the donation to a proton

(b) Methylcyanide to Ethylalcohol

CH CN+2H O3 2 H / HClNH Cl CH COOH3 H CH CH OH3 2

+ 4

→  →4 [ ]

methylcyanide acetic acid ethylalcohol

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SOLVED PAPER - 2018| 23 (c) Benzene diazonium chloride reacts with phenol in weak alkaline medium.

Benzenediazonium Phenol Parahydroxyazobenzone

Chloride + H2O + Cl–

Water Chloride ion

15 The most common sulphide ore of Copper is Chalcopyrite CuFeS2

The concentrated ore is heated strongly with SiO2, CaCO3, and air in a furnace to get pure Copper

The Cu2+ ions in CuFeS2 are reduced to Cu2+Sulphide which is further reduced to the Copper metal The iron ends up in an Fe (II)silicate slag which is removed Most of the sulphur in CuFeS2 turns into SO2 gas This is used

to make sulphuric acid via contact process

2 CuFeS2 + 2 SiO2 + 4 O2 → Cu2S + 2 FeSiO3 + 3 SO2

Cu2S is converted to copper with a final blast of air as Cu2S + O2 → 2 Cu + SO2

16 (a) (i) E°cell = Ecathodeο Right −Eanodeο Left

E°cell = −0.403 − (−0.763) V, or E°cell = 0.36 V

DG° = − nFE°cell

DG° = − (2 mol)(96485 Coulomb mol−1)(0.36 J Coulomb−1)

DG° = − 69.469 kJ

(ii) (1) Equivalent conductivity is defined as conducting power of all the ions produced by dissolving 1 g

equivalent of an electrolyte in solution Equivalent conductivity Λe = 1000 k/c, where k is the specific

conductivity and c is the concentration in molarity

(2) Corrosion of metals is the deterioration of a metal as a result of chemical reactions between the metal

and the surrounding environment which converts a refined metal to a more chemically stable form such as oxide, hydroxide, or sulphide

(b) (i) Molar conductivity Λm = k

c , where k is the specific conductivity and c is the concentration in molarity

k = 0.0058 ohm−1 cm−1 Mass of BaCl2 m a = 5 g, volume of solvent V = 1 L, molecular weight of BaCl2

M = 208 gm mol−1 Thus, c =

m M V

−1 m−1 molarity−1

Equivalent conductivity Λe = 1000Λm, hence Λe = 24.167 × 103 ohm−1 m−1 molarity−1

(ii) Electrochemical series is a series of chemical elements in order of their standard electrode potential

Hydrogen electrode is considered as having zero electrode potential Electro-positive elements are the ones having greater tendency than Hydrogen to lose electrons to their solution Thus they lie above Hydrogen in the series Those that gain electrons from their solutions are electro-negative elements lie below Hydrogen in the series Thus electro-positive elements tend to replace Hydrogen from acids

17 (a) (i) (1) Nitrogen does not form pentahalide as it has no d-orbitals in its valence shell, it cannot undergo sp3d

hybridisation and cannot extend its valency upto 5 due to the unavailability of d-orbitals.

(2) Helium is an inert gas, very less reactive and not flammable, and is less dense than air

(3) ICl is more reactive than I2 because the inter halogen compound tend to form weaker X-X bond than

X-X in halogens, thus making ICl less stable and more reactive than I2

(ii) (1) HClO4

ClO

O (-1)

O — H(+3)

(-1)

O(-1)

(2) H3PO3 O P O

HH

OH

(b) (i) (1) Mercury loses its meniscus in contact with ozone and sticks to the glass due to the formation of

mercurous oxide This is known as ‘tailing of mercury’ 2 Hg + O3 → Hg2O + O2

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(2) Halogens absorb radiation in the visible region and the valence electrons get excited to higher energy

levels The amount of energy required depends on the size of the atom F is the smallest element and the force of attraction between the nucleus and the outer electron is large As a result it requires large excitation energy and absorbs high energy violet light so it appears pale yellow I2 requires less excitation energy and absorbs yellow light of low energy and so appears dark violet The energy gap between HOMO and LUMO decreases as the following F2 > Cl2 > Br2 > I2

(3) Hydride of sulphur is a gas while hydride of oxygen is a liquid, as sulphur is less electro-negative

than oxygen, thus, there is no hydrogen bonding in H2S Sulphur has only weak van der Waal forces, thus, H2S is a gas at room temperature H2O has strong inter-molecular hydrogen bonding due to the high electro-negativity of oxygen

(ii) (1) 6 NaCl + 2 MnO2 + 7 H2SO4 → Mn2SO4 + 6 NaHSO4 + 3 Cl2 + 4 H2O

(2) 2 KMnO4 + 5 SO2 + 2 H2O → K2SO4 + 2 MnSO4 + 2 H2SO4

18 (a) (i) (1) Benzaldehyde with hydrazine

+ H N2 –NH2

C = OH

C = N–NH2H

+ H O2

Benzaldehyde hydrazine Water

(2) PCl5 + CH3COOH → CH3COCl + HCl + POCl3

Phosphorus Pentachloride acetic acid acetyl chloride Phosphorus oxychloride

(3) CH3COCH3 + NaHSO3 → C3H7NaO4S

Acetone Sodium Bisulphate Sodium 3-hydroxy Propane-1-sulphonate

(ii) (1) Litmus test : Ethanol does not show any change, while with acetic acid, blue Litmus turns to red (2) Acetaldehyde gives Iodoform test with I2 and alkalis, while benzaldehyde does not

(b) (i) (1) Clemmensen's Reduction :

Reduction of ketones to alkanes using zinc amalgam and HCl

H +

Zn (Hg)

C = OR

(3) Hell – Volhard – Zelinsky Reaction :

Carboxylic acid on reacting with Bromine and a-catalytic amount of phosphorus leads to

a-bromination of carboxylic acid

P (cot)-H PO3 3COOH + Br2

Br

(ii) (1) Acetaldehyde (CH3CHO) undergoes aldol condensation due to the presence of a-hydrogen attached

to the a-carbon but formaldehyde (HCHO) has no a-carbon attached to the functional group hence

no a-hydrogen is available for the reaction to occur

(2) In Acetic acid, CH3 is an electron donating group, thus it increases electron density towards O—H

bond making it difficult to remove the H+ to a base Formic acid (HCOOH), has no electron donating group, thus O-H bond is more polarised and can easily donate H+ ion making it more acidic

2Zn+2 +

Trang 26

ISC Solved Specimen Paper, 2018

(Issued by Board)

Class-XII

Chemistry Paper -I (Theory)

(Maximum Marks : 70) (Time allowed : Three hours)

All questions are compulsory Question 1 is of 20 marks having four sub parts, all of which are compulsory Question numbers 2 to 8 carry 2 marks each,

with any two questions having internal choice.

Question numbers 9 to 15 carry 3 marks each, with any two questions having an internal choice.

Question numbers 16 to 18 carry 5 marks each, with an internal choice.

All working, including rough work, should be done on the same sheet as, and adjacent to

the rest of the answer.

The intended marks for questions or parts of questions are given in brackets [J.

Balanced equations must be given wherever possible and diagrams where they are helpful.

When solving numerical problems, all essential working must be shown.

In working out problems, use the following data:.

Gas constant R = 1.987 cal deg –1 mol –1 = 8.314 JK -1 mol –1 = 0.0821 dm 3 atm 11 atm = / dm 3 atm = 101.3 J.

1 Faraday = 96500 coulombs Avogadro’s number = 6.023 × 10 23

1 (a) Fill in the blanks by choosing the appropriate

word/words from those given in the brackets :

[4 × 1]

(increases, decreases, efficient, same as, 68,

non-efficient, greater than, 74, less than, sp3d3, sp3d2,

octahedral, distorted octahedral, remains same)

(i) Both ccp and hcp are close

packing and occupy about _% of

the available space

(ii) The molar conductance of a

solution _ with dilution,

while its specific conductance

_with dilution

(iii) The geometry of XeF6 molecule is

_ and the hybridization of Xe

atom in the molecule is _

(iv) The acidic strength of phenol is

ethyl alcohol but nitro phenol

(b) Complete the following statements by

selecting the correct alternative from the choices

(i) The molal freezing point constant of water

is 1.86 K kg mol–1 Therefore, the freezing

point of 0.1M NaCl solution in water is

(1) Primary alcohol (2) Secondary alcohol (3) Carboxylic acid (4) Tertiary alcohol (iv) Which of the following ores can be

concentrated by froth floatation process : (1) Haematite

(2) Calamine (3) Zinc blende (4) Bauxite

(i) Disaccharide (a) Adsorption(ii) Arrhenius equation (b) Condensation

(iii) Dacron (c) Activation energy(iv) Freundlich isotherm (d) Sucrose

(d) Answer the following questions : [4 × 2]

(i) Calculate the mass of compound

(molar mass = 256 g mol–1) to be dissolved in 75 g of benzene to lower its freezing point by 0.48 K (Kf = 5.12 K kg mol–1)

Trang 27

(ii) Write the IUPAC name of the complex

[Cr(NH3)4Cl2]+ Which type of isomerism

will be exhibited by it?

(iii) Why do the transition elements have

higher enthalpies of atomisation?

In 3d series (Sc to Zn), which

element has the lowest enthalpy of

atomisation and why ?

(iv) Write balanced chemical equations for

Carbylamine reaction and Diazotization

reaction

2 (a) Identify the reaction order from each of the

following rate constants : [2]

(i) k = 2.3 x 10–5 L mol–1 s–1

(ii) k = 3 × 10–4 s–1

OR (b) Write two differences between ‘order of reaction’

and ‘molecularity of reaction’

3 (a) Differentiate between an antiseptic and a

(b) Name a biodegradable detergent.

4 What will be the major product obtained when

2-bromobutane reacts with alcoholic potassium

hydroxide? State the type of reaction involved in it

6 Explain the amphoteric behaviour of amino acids [2]

7 (a) How is phenol converted to benzoic acid? Explain

with the help of balanced chemical equations [2]

OR (b) Write the mechanism of acid dehydration of

ethanol to yield ethene [2]

8 A substance decomposes by following first order

kinetics If 50% of the compound is decomposed

in 120 minutes, how long will it take for 90% of the

compound to decompose ? [2]

9 (a) Calculate the amount of CaCl2 (molar mass = 111 g

mol–1) which must be added to 500 g of water to lower its

freezing point by 2 K, assuming CaCl2 is completely

dissociated (Kf for water = 1.86 K kg mol–1) [3]

OR (b) A solution containing 0.5 g of KCl dissolves in 100 g

of water and freezes at – 0.24° C Calculate the degree of

dissociation of the salt (Kf for water = 1.86°C) [3]

10 An element with density 10 g cm–3 forms a cubic

unit cell with edge length of 3 × 10–8 cm What is the

nature of the cubic unit cell if the atomic mass of the

element is 81 g mol–1 ? [3]

11 Give reasons for the following observations : [3]

(a) Physisorption decreases with an increase in

temperature

(b) Addition of alum purifies water.

(c) Brownian movement stabilizes colloidal

solutions

12 (a) What type of isomers are [Co(NH3)5Br]SO4

and [Co(NH3)5SO4]Br.? Give a chemical test to

distinguish between the two isomers [3] (b) Write the structures of optical isomers of the

complex ion [Co(en)2Cl2]+

13 (a) Account for the following/Explain why :

(i) Transition metals exhibit variable oxidation

states, (ii) Zr (Z = 40) and Hf (Z = 72) have almost

identical radii, (iii) Transition metals and their compounds act

OR (b) Complete the following chemical equations :

(i) K2Cr2O7+ H2SO4+FeSO4 ® (ii) K2Cr2O7 + H2SO4 + H2S ® (iii) KMnO4 + H2SO4 + H2C2O4 ® [3]

14 Arrange the following as directed : [3] (a) Increasing order of basic strength :

Aniline, p - nitroaniline and p - toluidine

(b) Decreasing order of basic strength in gas phase :

C2H5NH2, (C2H5)2NH, (C2H5)3N and NH3

(c) Increasing order of solubility in water :

C6H5NH2, (C2H5)2NH, C2H5NH2

15 How is silver extracted from its ore? Explain the

process with relevant equations [3]

16 (a) (i) Resistance of a conductivity cell filled with

0.1 mol L–1 KCl solution is 100 W If the resistance of the same cell when filled with 0.02 mol L–1 KCl solution is 520 Q, calculate the conductivity and molar conductivity of 0.02 mol L–1 KCl solution The conductivity

of 0.1 mol L–1 KCl solution is 1.29 x 10–2 W–1

cm–1 (ii) Define the following terms : (1) Limiting molar conductivity

(2) Fuel cell [5]

OR (b) (i) Calculate emf of the following cell at 298 K :

Mg(s) | Mg2+ (0.1 M) || Cu2+ (0.01M) | Cu(s) [Given E°cell = +2.71 V, 1 Faraday = 96500 C

mol–1] (ii) State Faraday’s first law of electrolysis

Calculate the charge required in terms of Faraday for the reduction of 1 mole of Cu2+

17 (a) (i) Account for the following/Explain why :

(1) Interhalogens are more reactive than

halogens

(2) N2 is less reactive at room temperature (3) Reducing character increases from NH3

to BiH3 (ii) Draw structures of the following : (1) H4P2O7

OR (b) (i) Account for the following/Explain why :

(1) PCl5 exists but NCl5 does not

(2) Fluorine is a stronger oxidising agent

than chlorine

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SPECIMEN PAPER-2018 | 27

(3) Bond enthalpy of F2 is less than that of

Cl2 (ii) Complete and balance the following

(ii) Give one chemical test each to distinguish

between the following pairs of compounds : (i) Benzaldehyde and Benzoic acid (ii) Propanal and Propanone [5]

OR (b) (i) Write the chemical equations to illustrate the

following name reactions : (1) Wolff-Kishner reduction

(2) Aldol condensation

(3) Cannizzaro reaction, (ii) Account for the following : (1) CH3CHO is more reactive with HCN

than CH3COCH3 (2) Carboxylic acids are stronger acids than

ll

SOLUTIONS

1 (a) (i) efficient, 74

(ii) increase, decrease

(iii) distorted octahedral, sp3d3

(b) (i) (2) – 0.372°C

(ii) (4) CH3 – Br

(iii) (2) Secondary alcohol

(c) (i) Disaccharide–Sucrose

(ii) Artheneus equation–Activation energy

(iii) Dacron–Condensation polymer

(d) (i) MB = 256 mol–1, WA = 75 g, Kf = 5.12 K kg mol–1, DTf = 0.48 K

M

1000W

(iii) Transition elements have high effective nuclear charge and a large number of valence electrons Therefore,

they form very strong metallic bonds which arise due to the presence of unpaired electron in the (n – 1)

d subshell resulting in high enthalpy of atomisation.

Zn has the lowest enthalpy of atomisation due to the absence of unpaired electrons and weak metallic

Trang 29

Order of reaction Molecularity of reaction

(i) It is the sum of the powers of the concentration of

the reactants in the rate law expression (i) It is the number of reacting species taking part in an elementary reaction, which must collide

simultaneously resulting into a chemical reaction.(ii) It is determined experimentally (ii) It is a theoretical concept

[2]

3 (a)

Antiseptic Disinfectant

(i) Antiseptics are applied to living tissues such as

wounds, cuts, ulcers, diseased skin surfaces (i) Disinfectant are applied to ianimate object such as floors, drains, instruments, etc.(ii) They do not cause any harm (ii) They sometimes cause adverse effects when used

on skin

4 When 2-bromobutane reacts with alcoholic potassium hydroxide resulting in the formation but-2-ene and

6 In aqueous solution, the carboxyl group of an amino acid can lose a proton and the amino acid group can accept a

proton to give a dipolar ion known as zwitter ion

R CH C

O

OO

Trang 30

SPECIMEN PAPER-2018 | 29

7 (a) Phenol is converted to benzoic acid by following steps :

— Conversion of phenol to benzene by treatment with zinc

— Friedal craft alkylation of benzene to form toluene

— Oxidation of toluene to benzoic acid by potassium permanganate

OR (b) The mechanism of acid dehydration of ethanol to yield ethene involves the following three steps :

Step 1 : Protonation of ethanol to form ethyl oxonium ion.

H

H

|C

|H

H

|C

|H

O H H Fast H

H

|C

|H

H

|C

|H

H

|

    + +   O

+H Ethanol Protonated ethanol

(Ethyl oxonium ion)

Step 2 : Formation of carbocation

H

H

|C

|H

H

|C

|H

H

| O H

SlowH

H

|C

|H

H

|C

|H

|H

H

|C

|H

t

120

For the first order reaction,

log[ ][ ]

k

AA

5 77 10 3 10

× − log

1 86

×

OR

(b) w = 0.5 g, K f = 1.86°C, W = 100 g

Ethene

Trang 31

m = K

T W

f f

× ×

× = 38.75 Molecular mass of KCl = 74.5

Van’t Hoff Factor, i = normal molar mass

observed molar mass

38 75 1 92

= . KCl ¾® K+ + Cl–

Moles after dissocation 1 – a a a

Total no of moles after dissociation = 1 + a

Normal moles of solute =α 1+

1

11+ α = 1.92

11 (a) In physisorption adsorbate and adsorbent are held by weak vander Waal’s forces which break easily on

(b) Alum’s fine particles load themselves on the suspended particles to speed up the sedimentation and allowing

the suspended particles to flocculate and settle down which can be removed [1] (c) Brownian movement is caused by the unbalanced bombardment of the colloidal particles of the molecules

of the dispersion medium It has a stirring effect and helps in providing stability to colloidal solutions by not

12 (a) Ionisation isomers :

[Co(NH3)5Br] SO4 is red-violet An aqueous solution gives a white precipitate of BaSO4 and BaCl2 solution In contrast [Co(NH3)5SO4] Br is red A solution of this complex does not give a positive sulphate test with BaCl2

Trang 32

SPECIMEN PAPER-2018 | 31(b)

13 (a) (i) In transition elements, the energies of (n – 1) d orbitals and ns orbitals are nearly same Therefore,

electrons from both can participate in bond formation and hence show variable oxidation states [1]

(ii) This is because of filling of 4f orbitals which have poor shielding effect (lanthanoid contraction) [1]

(iii) Due to the following reasons :

(a) Transition metal form unstable intermediate compounds because of their variable oxidation states and

give a new path with lower activation energy for the reaction

(b) They provide large surface area with free valencies on which reactants are adsorbed [1]

OR (b) (i) K2Cr2O7 + 7H2SO4 + 6FeSO4 ¾® Cr2(SO4)3 + 3Fe2(SO4)3 + K2SO4 + 7H2O

(ii) K2Cr2O7 + H2SO4 + H2S ¾® K2SO4 + Cr2(SO4)3 + 3S + 7H2O

(iii) 2KMnO4 + H2SO4 + 5H2C2O4 ¾® K2SO4 + 2MnSO4 + 8H2O + 10CO2 [3]

14 (a) p-nitroaniline < aniline < p-toluidine.

(b) (C2H5)3N > (C2H5)2NH > C2H5NH2 > NH3

15 Silver is extracted from the argentite ore by the Mac-Arthur and Forrest’s cyanide process The various steps

involved in this process are as follows :

(a) Concentration : The crushed ore is concentrated by froth floatation process.

(b) Treatment of ore with NaCN : The concentrated ore is treated with 0.4 – 0.6% solution of sodium cyanide This

mixture is agitated by a current of air So that Ag present in the ore is converted into soluble sodium argento complex

Ag2S + 4NaCN ¾® 2Na [Ag(CN)2] + Na2S

(c) Precipitation of Silver : The solution containing sodium argento cyanide is filtered to remove insoluble

impurities and filtrate is treated with zinc dust, silver gets precipitated

2Na[Ag(CN)2] + Zn ¾® Na2 [Zn(CN)4] + 2Ag

(d) Electrolytic refining : Impure silver is made anode and a thin sheet of pure silver act as cathode Silver nitrate

acidified with 1% nitric acid acts as an electrolyte On passing electricity pure silver gets deposited at the

Molar conductivity ∧m = 103 k/m

0 02

3× × −3

[1]

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(ii) (1) Limiting molar conductivity can be defined as the value of molar conductivity when the concentration

approaches zero

(2) Fuel cells are those cells which produce electrical energy directly from the combustion of fuels such as

OR (b) (i) At anode : Mg ¾® Mg2+ + 2e

+

− 0 0592

22

.log[ ][ ] (at 298 K) Here, E°cell = 2.71 V, [Mg2+] = 0.1 M, [Cu2+] = 0.01 M, n = 2

(ii) Faraday’s first law of electrolysis : The amount of any substance deposited or liberated at the electrode is

directly proportional to the quantity of electricity passing through the electrolyte

Cu2+ + 2e– ¾® Cu \ Quantity of charge required for reduction of 1 mol of Cu2+ = 2F [5]

17 (a) (i) (1) Interhalogens are more reactive than halogens (except F) because A–X bonds in dihalogen

interhalogens are weaker than the X–X bonds in dihalogen molecules

(2) Because dinitrogen is formed by sharing three electron pairs between two nitrogen atoms resulting

into the triple bond As a result the bond dissociation energy is quite high causing N2 to be less reactive

(3) The reducing character depends upon the stability of the hydride Since BiH3 is the least stable (least

electronegative) than other elements in the group, therefore they can easily donate electron pair Therefore, reducing character increases from NH3 to BiH3

XeF

F

OR

(b) (i) (1) Nitrogen with n = 2 contains s and p orbitals only It does not have d orbitals to expand its covalency

beyond four Therefore, NCl5 does not exist Whereas in PCl5, P has vacant 3d orbital to which 3s

electrons can be excited to make available five half filled orbitals needed for the formation of five P –

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(2) 2C6H5CHO + conc.NaOH ¾® C6H5CH2OH + C6H5COONa

Benzyl alcohol Sodium benzoate

(3) CH3COOH Cl /P ClCH2 → 2COOH + HCl

Chloroacetic acid

(ii) Test to distinguish between benzaldehyde and benzoic acid :

Benzoic acid being an acid reacts with NaHSO3 solution to give brisk effervescence due to evolution of

CO2 while benzaldehyde does not response to this test

CHO

+ NaHCO3 No effervescence due to evolution of CO gas2

Benzaldehyde

(2) Test to distinguish between propanal and propanone : Propanal being an aldehyde reduces Tollens reagent

to silver mirror but propanone being a ketone does not

CH3CH2CHO + 2 [Ag(NH3)2]+ + 3OH– ¾® CH3CH2COO– + 2Ag ¯ + 4NH3 + 2H2O

Propanal

CH3COCH3 Tollens' reagent No silver mirror→

OR (b) (i) Wolff kishner reduction :

O

HHH

(3) Cannizzaro reaction :

2HCHO conc KOH CH→ 3OH + HCOO–K+

Formaldehyde Methyl alcohol Potassium formate

(ii) (1) CH3CHO is more reactive than CH3COCH3 due to smaller +I effect of one methyl group CH3CHO is

less hindered than CH3COCH3 towards (Nu–) Therefore, nucleophilic addition reactions occur more in

CH3CHO

(2) Carboxylic acids are acidic because of resonance stabilisation of carboxylate anion while phenols are acidic

due to resonance stabilisation of phenoxide ion Carboxylic acids are more acidic than phenols because the negative charge in carboxylate ion is more spread out than phenoxide ion as there are two electronegative O-atoms in carboxylate anion in comparison to phenoxide ion [5]

ll

[5]

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ICSE Examination Paper, 2017*

With Marking Scheme, (Qualitative Analysis)

Chemistry

(Maximum Marks : 70) (Time allowed : Three hours)

(Candidates are allowed additional 15 minutes for only reading the paper.

They must NOT start writing during this time.)

1 Answer all questions in Part I and six questions from Part II, choosing two questions from Section A, two from Section B and two from Section C

2 All work including rough work, should be done on the same sheet as, and adjacent to, the rest of the answer

3 The intended marks for questions or parts of questions are given in brackets [ ]

4 Balanced equations must be given wherever possible and diagrams where they are helpful

5 When solving numerical problems, all essential working must be shown

6 In working out problems use the following data :

Gas constant R = 1.987 cal deg–1 mol–1 = 8.314 JK–1 mol–1 = 0.0821 dm3 atm K–1 mol–1

1l atm = 1 dm3 atm =101.3 J 1 Faraday = 96500 Coulombs

(i) Calcium acetate on heating gives which gives on heating with iodine and sodium

hydroxide solution

(ii) On dilution of a solution, its specific conductance while its equivalent conductance

(iii) Sucrose is a and yields upon hydrolysis, a mixture of and fructose

(iv) More is the standard reduction potential of a substance, the is its ability to displace

hydrogen from acids

(v) An aqueous solution of CH3COONa is due to

(b) Complete the following statements by selecting the correct alternative from the choices given : [5] (i) In a face centered cubic lattice, atom (A) occupies the corner positions and atom (B) occupies the face centre

positions If one atom of (B) is missing from one of the face centered points, the formula of the compound is :

(ii) The half-life period of a first order reaction is 20 minutes The time required for the concentration of the

reactant to change from 0·16 M to 0·02 M is :

(1) 80 minutes (2) 60 minutes

(3) 40 minutes (4) 20 minutes

(iii) For a spontaneous reaction ΔG° and E° cell will be respectively :

(1) –ve and +ve (2) +ve and –ve

(3) +ve and +ve (4) –ve and – ve

(iv) The conjugate acid of HPO42− is :

(3) H2PO4− (4) PO43–

* For Explanatory Answers, please refer to the Answer in the relevant chapter/Topic of the Question Bank.

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EXAMINATION PAPER - 2017| 35 (v) The polymer formed by the condensation of hexamethylenediamine and adipic acid is :

(i) Why the freezing point depression (ΔTf) of 0·4M NaCl solution is nearly twice than that of 0·4M glucose

solution ?

(ii) Identify the order of reaction from each of the following units of rate constant (k) :

(a) mol L–1 sec–1

(i) Diazotisation (a) Bakelite

(ii) Argentite (b) Nernst equation

(iii) Thermosetting plastics (c) Aniline

(Freezing point of water = 273 K, Kf for water = 1·87K kg mol–1, at wt C = 12, H = 1, O = 16)

(ii) A 0·15 M aqueous solution of KCl exerts an osmotic pressure of 6·8 atm at 310 K Calculate the degree of dissociation of KCl (R = 0·0821 Lit atm K–1 mol–1) [2]

(iii) A solution containing 8·44 g of sucrose in 100 g of water has a vapour pressure 4·56 mm of Hg at 273K If the vapour pressure of pure water is 4·58 mm of Hg at the same temperature, calculate the molecular weight of

(b) (i) When ammonium chloride and ammonium hydroxide are added to a solution containing both Al3+ and

Ca2+ ions, which ion is precipitated first and why ? [2]

(ii) A solution of potassium chloride has no effect on litmus whereas, a solution of zinc chloride turns the blue

(c) How many sodium ions and chloride ions are present in a unit cell of sodium chloride crystal ? [1] Question 3

(a) (i) Lead sulphide has face centered cubic crystal structure If the edge length of the unit cell of lead sulphide is

(at wt Pb = 207, S = 32)

(ii) For the reaction: 2H2 + 2NO  2H2O + N2 , the following rate data was obtained : [3]

S No [NO] mol L –1 [H 2 ] mol L –1 Rate : mol L –1 sec –1

Calculate the following :

(1) The overall order of reaction

(2) The rate law

(3) The value of rate constant (k).

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(b) (i) The following electrochemical cell is set up at 298 K : [2]

Zn / Zn2+ (aq) (1M) || Cu2+ (aq) (1M) / Cu

Given → E°Zn2+ / Zn = – 0.761 V, E°Cu2+ / Cu = + 0.339 V

(1) Write the cell reaction

(2) Calculate the emf and free energy change at 298 K

(1) What is the effect of temperature on ionic product of water (Kw) ?

(2) What happens to the ionic product of water (Kw) if some acid is added to it ?

(c) Frenkel defect does not change the density of the ionic crystal whereas, Schottky defect lowers the density of ionic

Question 4

(a) (i) Name the law or principle to which the following observations conform : [3]

(1) When water is added to a 1·0 M aqueous solution of acetic acid, the number of hydrogen ion (H+)

increases

(2) When 9650 coulombs of electricity is passed through a solution of copper sulphate, 3·175 g of copper is

deposited on the cathode (at wt of Cu = 63·5)

(3) When ammonium chloride is added to a solution of ammonium hydroxide, the concentration of hydroxyl

ions decreases

(ii) What is the difference between the order of a reaction and its molecularity ? [2] (b) (i) Explain why high pressure is required in the manufacture of sulphur trioxide by contact process State the

(ii) Calculate the equilibrium constant (Kc) for the formation of NH3 in the following reaction : [1]

N2(g) + 3H2(g)  2NH3(g)

At equilibrium, the concentration of NH3, H2 and N2 are 1·2×10–2, 3·0×10–2 and 1·5×10–2 M respectively

(i) Hydrolysis of ester (ethyl acetate) begins slowly but becomes fast after sometime

(ii) The pH value of acetic acid increases on addition of a few drops of sodium acetate

Section B

Attempt any two questions.

Question 5

(i) Potassium trioxalatoaluminate(III)

(ii) Hexaaquairon(II) sulphate

(i) [Cu (NH3)4] [PtCl4] and [Pt(NH3)4] [CuCl4]

(ii) [Co(Pn)2Cl2]+ and [Co(tn)2Cl2]+

(i) Give the IUPAC name of the complex ion

(ii) What is the oxidation number of cobalt in the complex ion ?

(iii) State the type of hybridisation of the complex ion

(iv) State the magnetic behaviour of the complex ion

Question 6

(i) Potassium permanganate is heated with concentrated hydrochloric acid

(ii) Lead sulphide is heated with hydrogen peroxide

(iii) Ozone is treated with potassium iodide solution

(b) Discuss the theory involved in the manufacture of sulphuric acid by contact process [2] Question 7

(a) (i) What are the types of hybridisation of iodine in interhalogen compounds IF3, IF5 and IF7, respectively ? [3] (ii) Draw the structure of xenon hexafluoride (XeF6) molecule and state the hybridisation of the central atom

(b) Give the balanced equations for the conversion of argentite (Ag2S) to metallic silver [2]

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EXAMINATION PAPER - 2017| 37Section C

Attempt any two questions.

Questions 8

(a) How can the following conversions be brought about :

(b) (i) How will you distinguish between primary, secondary and tertiary amines by Hinsberg’s test ? [1] (ii) Why do alcohols possess higher boiling points as compared to those of corresponding alkanes ? [1]

(i) C6H5COOH PCl5→ A H Pd/BaSO B 2 − 4→ KCNalc

(i) Friedel-Crafts reaction (alkylation)

(ii) Williamson’s synthesis

(iii) Aldol condensation

(i) Ethyl alcohol and sec-propyl alcohol

(ii) Acetaldehyde and acetic acid

(ii) Give the chemical equation for the reaction of (C) with chlorine in the presence of red phosphorous and name

the reaction

(i) What is the common name of the polymer obtained by the polymerization of caprolactum ? Is it an addition

polymer or a condensation polymer ?

(ii) Name the two organic compounds which have the same molecular formula C2H6O Will they react with PCl5 ?

If they react, what are the products formed ?

(i) Methyl magnesium bromide with ethyl alcohol

(ii) Acetic anhydride with phosphorous pentachloride

(iii) Acetaldehyde with hydroxylamine



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Marking Scheme (Qualitative Analysis)

Issued by CISCE

1 (a) (i) acetone, iodoform

(ii) decreases, increases

(iii) disaccharide, glucose

(iv) negative, greater

(v) basic, anionic hydrolysis

Number of moles increases (doubles) in NaCl solution

Hence, the depression in freezing point is nearly twice than that of glucose solution

(ii) (a) Zero order reaction

(d) Match the following :

(i) Diazotisation (c) Aniline

(ii) Argentite (e) Froth floatation process

(iii) Thermosetting plastics (a) Bakelite

(iv) Electrochemical cell (b) Nernst equation

(v) Bidentate ligand (d) Ethylenediamine

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EXAMINATION PAPER - 2017| 39

Comments of Examiners

(a) (i) Many candidates wrote ‘acetaldehyde’ instead of ‘acetone’ in the first blank A few candidates wrote ‘chloroform’

instead of ‘iodoform’ in the second blank.

(ii) Many candidates interchanged (reversed) the answer instead of ‘decreases’ and ‘increases’ they wrote ‘increases’ and

‘decreases’.

(iii) Instead of ‘disaccharide’ many candidates wrote ‘polysaccharide’ in the first blank Few wrote ‘lactose’ in place of

‘glucose’ for the second blank.

(iv) Some candidates wrote ‘positive’ instead of ‘negative’ in the first blank For the second blank, instead of ‘greater’ a few candidates wrote ‘more’ which was not given in the list of words.

(v) Some candidates wrote ‘acidic’ in place of ‘basic’ in the first blank Instead of ‘anionic hydrolysis’ some candidates wrote ‘cationic hydrolysis’ in the second blank.

(b) (i) Some candidates wrote A 2 B 3 or A B 2 instead of A 2 B 5

(ii) Most of the candidates were able to calculate the answer correctly i.e 60 minutes but some candidates wrote 40 minutes

or 20 minutes also.

(iii) The correct option was ‘–ve and +ve’ but some candidates gave incorrect options also.

(iv) Instead of H 2 PO 4 – some candidates wrote other options such as PO 4 3– , H 3 PO 4 etc which were not correct.

(v) Instead of Nylon-66 which was the correct answer, some candidates wrote Dacron or Teflon which was not correct (c) (i) Many candidates wrote that NaCl is a strong electrolyte and glucose is a non-electrolyte However, they were not able

to explain that colligative property is directly proportional to number of moles in solutions In a few cases, van’t Hoff factor was not given.

(ii) Instead of zero order and 2 nd order reaction,some candidates wrote 1 st order and zero order reaction.

(iii) Most of the candidates calculated the value of molar conductivity correctly, but some candidates wrote the answer with incorrect unit.

(iv) Instead of zero order reaction some candidates wrote first order and second order reactions.

(v) Most of the candidates failed to explain that OH group is ortho and para directing group The concept of directive influence was not very clear to many candidates.

(d) Most of the candidates attempted this part correctly A few candidates gave incorrect answers also, such as diazotization was matched with ethylenediamine and bidentate ligand was matched with aniline.

SUGGESTIONS FOR TEACHERS

Insist upon writing organic reactions with conditions.

The relationship between specific conductance, equivalent conductance,specific conductivity and molar conductivity should be

explained to students.

Ask students to learn carbohydrates,types of carbohydrates, chemical properties, etc.

Electrochemical series and identification of anode and cathode on the basis of standard electrode potential must be explained

thoroughly to students.

Salt hydrolysis of all types of salts must be explained with suitable examples.

Explain the calculations to find the number of atoms in various types of cubic unit cells Give practice to find the formula of

the compound.

More practice should be given in numerical problems based on half-life period.

Instruct students to write the answer to any numerical problem with correct unit.

Explain the conditions for spontaneous process in terms of ΔG°and E° to the students.

Bronsted-Lowry concept and conjugate acid – base pairs should be explained clearly to the students.

Monomers and their polymers should be explained in a tabular form.

Explain how the value of van’t Hoff factor changes for electrolytes and non-electrolytes by taking different examples Give adequate practice in class in calculating the units of rate constant(k)for different order reactions.

Sufficient practice should be given to students to represent zero, first and second order reactions graphically.

Directive influence of various functional groups in aromatic compounds should be clearly explained to students.

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