Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019)

Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019) Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019) Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019) Preview Theory and Problems for Chemistry Olympiad Challenging Concepts in Chemistry by Zhihan Nan (2019)

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Published by

World Scientific Publishing Co Pte Ltd.

5 Toh Tuck Link, Singapore 596224

USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601

UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE

Library of Congress Cataloging-in-Publication Data

Names: Nan, Zhihan, author | Zhang, Sheng (Lecturer in chemistry), author

Title: Theory and problems for Chemistry Olympiad : challenging concepts in chemistry /

Zhihan Nan, Sheng Zhang

Description: New Jersey : World Scientific, [2020] | Includes index

Identifiers: LCCN 2019030146 | ISBN 9789813238992 (hardcover) |

ISBN 9789811210419 (paperback)

Subjects: LCSH: International Chemistry Olympiad Study guides |

Chemistry Problems, exercises, etc

Classification: LCC QD42 N32 2019 | DDC 540.76 dc23

LC record available at https://lccn.loc.gov/2019030146

British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library.

Copyright © 2020 by World Scientific Publishing Co Pte Ltd

All rights reserved This book, or parts thereof, may not be reproduced in any form or by any means,

electronic or mechanical, including photocopying, recording or any information storage and retrieval

system now known or to be invented, without written permission from the publisher.

For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance

Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA In this case permission to photocopy

is not required from the publisher.

For any available supplementary material, please visit

https://www.worldscientific.com/worldscibooks/10.1142/10960#t=suppl

Typeset by Stallion Press

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Printed in Singapore

Foreword by Professor Richard Wong vii

Attributions ix

1 Introduction and General Tips to Prepare for Chemistry Olympiad 1

2.1 Thermodynamics 6

2.2 Chemical Equilibria 39

2.3 Thermodynamics of Phase Transitions 61

2.4 Thermodynamics of Mixtures 70

2.5 Electrochemistry 90

2.6 Reaction Kinetics 101

3.1 Atomic Structure and Quantum Theory 122

3.2 Periodicity 134

3.3 Chemical Bonding 137

3.4 Acid-Base Chemistry 149

3.5 Main Group Chemistry 153

3.6 Crystal Structure 184

3.7 Coordination Chemistry 197

4.1 Introduction to Organic Chemistry 226

4.2 Optical Activity and Stereochemistry 236

4.3 Conjugation and Aromaticity 245

vi Theory and Problems for Chemistry Olympiad

4.4 Acidity, Basicity, Nucleophilicity and Electrophilicity of

Organic Compounds 252 4.5 Radical Chemistry 263

4.6 Nucleophilic Addition 277

4.7 Nucleophilic Substitution 289

4.8 Elimination Reactions 314

4.9 Electrophilic Addition 326

4.10 Electrophilic Substitution 336

4.11 Enolate Chemistry 350

4.12 Oxidation and Reduction 368

4.13 Protecting Groups in Organic Chemistry 381

4.14 Pericyclic Reactions 386

4.15 Organometallic Chemistry 400

4.16 Retrosynthetic Analysis 408

5.2 Techniques in Organic Synthesis 425

5.3 Qualitative Analysis 430

6 Sample Problems and Solutions 444

6.1 Sample Problem Set 447

6.2 Solutions to the Sample Problems 464

The International Chemistry Olympiad (IChO) celebrated its 50th anniversary in

2018, growing from a small competition with only 3 participating countries and 18

competing students to what it is now — a worldwide event attracting 76 countries

and 300 students To select a team of students to represent Singapore at IChO, the

Singapore Chemistry Olympiad (SChO) was launched in 1989 and it has become an

annual event since then

Chemistry Olympiad aims to motivate pre-tertiary students to study beyond

the syllabus and stimulate their thinking through solving challenging chemistry

problems It is able to further develop the interest of pre-tertiary students in

chem-istry and improve chemchem-istry education by providing interested students with more

resources

This book is the first textbook that caters specifically to students preparing for

the Chemistry Olympiad competition Previously, eager students had to browse

through many university level textbooks to gain bits and pieces of information in the

different fields of chemistry The objective of this book is to bring down university

level concepts to pre-tertiary students in a concise manner, combining important

knowledge from all fields of chemistry into one book The book presents chemical

concepts in a succinct fashion, with key focus on the logical flow of concepts Clear

explanations are given such that students are able to fully understand the theories

presented

As I read through the draft of “Theories and Problems for Chemistry Olympiad”,

I was impressed by how the concepts taught in university are linked to the topics

familiar to pre-tertiary students The knowledge gap was bridged through detailed

justification, with every physical chemistry equation derived and every organic

reaction described by its mechanism It was a joy to read through as there were

many figures and diagrams used to illustrate the concepts The writing is clear and

easy to read, so it should help even a beginner get his/her bearing In particular, the

pedagogy is effective in keeping readers engaged as each chapter connects to the

next At the end of the book, students are also able to test their understanding by

attempting sample IChO problems with detailed solutions

FOREWORD

viii Theory and Problems for Chemistry Olympiad

Nan Zhihan has participated in IChO 2016, achieving a gold medal and the

IUPAC prize for highest score in the experimental examination After participating

in the competition, he has devoted much of his efforts in mentoring and training

the Singapore team for IChO 2017, 2018 and 2019 As a gold medallist, he

understands the requirements and challenges in preparing for the competition

and shares his personal experience in this book Dr Zhang Sheng is a lecturer at

the Department of Chemistry, NUS, and has been the mentor of the Singapore

Chemistry Olympiad team for 9 years, training and leading the Singapore team for

International Chemistry Olympiad competitions Over the years of his mentorship,

Singapore team has won a total of 16 Gold Medals and 19 Silver Medals in IChO

With vast experience in Chemistry Olympiad training, Nan Zhihan and Zhang Sheng

form a formidable team to complete this valuable resource for perspective students

I believe that this book is a valuable companion for students preparing for the

Chemistry Olympiad competition However, I would also recommend this book to

any student curious to learn more about chemistry, including freshmen at university

With Chemistry Olympiad gaining prominence, I encourage interested students to

take up the challenge and discover their passion in chemistry

Professor Wong Ming Wah, Richard

Head, Department of Chemistry National University of Singapore

Chapter 2.5

Figure 2.5.4: Sample galvanic cell by Hazmat2 is from Wikipedia commons

Chapter 3.1

Figures 3.1.2 to 3.1.4 and 3.1.6: Orbital Graphs by As6673 are from Wikipedia

commons, licensed under CC BY-SA 3.0

Chapter 3.6

Figure 3.6.2: Monoclinic cell by Fred the Oyster from Wikipedia commons, licensed

under CC BY-SA 3.0 Modified to describe the 7 crystal systems

Figure 3.6.3: Primitive cubic unit cell by DaniFeri from Wikipedia commons, licensed

under CC BY-SA 3.0

Figure 3.6.4 and Figure 3.6.7: Body-centred cubic unit cell by Chris He from

Wiki pedia commons, licensed under CC BY-SA 4.0 Each figure has been modified

to show only 1 unit cell Atom labels are added for CsCl unit cell

Figure 3.6.5: Face-centred cubic unit cell by Christophe Dang Ngoc Chan from

Wikipedia commons, licensed under CC BY-SA 3.0 Modified to show only 1 unit

cell

Figure 3.6.6: NaCl lattice by Prolineserver from Wikipedia commons, licensed under

CC BY-SA 3.0 Atom labels were added to the lattice

Figure 3.6.8 and Figure 3.6.9: Fluorite and Zinc Blende crystal structure by Tem5psu

from Wikipedia commons, licensed under CC BY-SA 4.0 Each figure has been

modified to show only 1 unit cell Atoms are labelled for both crystal structures

Figure 3.6.11: Spinel unit cell by Andif1 from Wikipedia commons, licensed under

CC BY-SA 4.0 Atoms are labelled on the figure

Figures 3.6.12 to 3.6.14: Figures for the types of crystal defects by VladVB from

Wikipedia commons, licensed under CC BY-SA 3.0

ATTRIBUTIONS

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Welcome to Chemistry Olympiad! Chemistry

Olympiad is a challenging competition that

tests students on their higher-order thinking

ability and encourages interested high school

students to read up beyond the syllabus This

book was written to explain tough university

chemistry concepts to high school students,

by building up the student’s knowledge slowly

starting from the basics When reading this

book, please appreciate the logical flow of

concepts and find the links between different

topics With time, I hope that you will see the

beauty in chemistry, and have an enriching

journey through Chemistry Olympiad

1 INTRODUCTION AND

GENERAL TIPS TO PREPARE FOR CHEMISTRY OLYMPIAD

2 Theory and Problems for Chemistry Olympiad

As the flow of chapters and content in this book is meticulously designed, I would

urge you to read the book following the order of the chapters and sub-chapters This

will ensure that you have the proper background knowledge required to understand

every chapter fully After completing the book once, it can be used as a reference

book to refresh yourself on the relevant topics once in a while

As a tip, it will be good to keep a notebook to write down important concepts

and equations while reading the book From the derivations of equations in physical

chemistry to the mechanisms in organic chemistry, it is important to try these on

your own to fully understand the concepts While looking at complicated reactions

or concepts, keep questioning in your head why each step proceeds the way it does

Note down any questions you have and ask your supervisor While the learning curve

is definitely steep, I am sure that the rewards are worth every bit of time and effort

The journey through Chemistry Olympiad is most rewarding when you are driven

by your interest in chemistry and curiosity to learn more, instead of just going for a

medal in the competition

In Chemistry Olympiad, the competition is the final challenge to test your ability

In most countries, there are various national Olympiad competitions to select

stu-dents for the International Chemistry Olympiad (IChO), the dream for most aspiring

Chemistry Olympians After all the hard work that is put into learning chemistry, it

is critical to perform to the best of your ability at the competition Here, the authors

list some tips from experience to help students do their best at the competition

For any competition, stress and mood through the examination play a

sig-nificant role in how well we can think When years of hard work culminate in a

5-hour long examination, it is difficult to not be overwhelmed by stress Thus, you

should face every competition with excitement, thinking of the competition as a

new opportunity to learn more chemistry through problem-solving Even if you

are unsure of the solution to certain problems, do not let it discourage you, as

the Olympiad competition is designed to be challenging In the end, it is not the

results that matter the most, but that you have given your best effort through the

journey of learning chemistry

Upon starting the paper, browse through all the questions first Generally,

Olympiad questions are not ranked by difficulty level In particular, while one student

may find an organic chemistry question more challenging, another student may

have a difficult time solving a physical chemistry question In the Olympiad

compe-tition, many students will find themselves having insufficient time to complete all

the questions Thus, find the questions that you are most confident in solving, and

ensure that they are completed correctly and efficiently before attempting the more

challenging problems

For some common constants, you should use the value that is given in the

“Constants and Formulae” table in front of the paper, regardless whether the value

is the same or different compared to the value you have memorised For example, the

Introduction and General Tips to Prepare for Chemistry Olympiad 3

speed of light is given asc 3.000 10 m s= × 8 ⋅ - 1 (IChO 2011) and c 2.998 10 m s= × 8 ⋅ - 1

(IChO 2018) You should also use the atomic mass from the Periodic Table given in

the question paper For example, the mass of a hydrogen atom was given as 1.01

(IChO 2010), 1.008 (IChO 2011) and 1.00794 (IChO 2015)

For physical chemistry questions, it is important to show full workings on how the

answer was obtained Sometimes, there might be small errors during the calculation

that lead to a different answer If the final answer is incorrect, points may be awarded

for correct equations in the working To avoid losing all the points due to a small

care-less error, please show all key steps leading to the final answer This also helps when

checking the answer again for any errors While working through physical chemistry

problems, it is recommended to leave your answers in symbolic form while working

through the problem This makes it easier to spot any algebraic errors, and minimise

the time spent on pressing the calculator If any intermediate value is obtained, try

to leave it to 1 or 2 more significant figures than the final required answer You do

not need to copy down all the decimal places from your calculator, because that’s

just a waste of your time and it will not affect your final results

As per all scientific calculations, standard rules for decimal places and significant

figures apply in Chemistry Olympiad calculation If a question requires students to

report the results to a certain number of significant figures, such requirement should

be stated clearly in the question If a question has not stated such a requirement, then

you just need to report your value with a reasonable number of significant figures

For example, a concentration of 0.1028 mol dm⋅ - 3 or 0.103 mol dm⋅ - 3 is reasonable,

but 0.102774125 mol dm⋅ - 3 is obviously not reasonable although that’s the value

shown on the calculator

For inorganic chemistry, it is important to be familiar with the properties of

different elements and ions, such as the colour of transition metal cations in their

various oxidation states, the flame test results of cations, common oxidation states

of elements, solubility of common inorganic salts and colour of common precipitates

This information will often give intuition into the identity of unknown compounds

in inorganic elucidation questions While a summary is provided in the qualitative

analysis Table 5.1, I would still encourage students to test out reactions and make

the observations themselves

You should also memorise the atomic mass of common elements, as this will

allow you to easily access molecular masses of common compounds This may be

useful to deduce the identity of inorganic compounds in calculation-type questions

For example, a molecular mass of 18 suggests H O2 , 28 suggests CO, and 44 suggests

2

CO Now, try the following for yourself: 98, 100, 160 Of course, there are still many

others You should try to summarise your own table of common molecules and their

molecular masses

Other than deducing compound identity through calculations, it is also possible

to make good judgements based on periodicity and the trends within each group