3 CHEMICAL HYGIENE PLAN CHP3.1 PurposeThis Chemical Hygiene Plan CHP sets forth policies, procedures, equipment, personal protective equipment and work practices that are capable of prot
Personal Protective Equipment (PPE) and Safe Attire
1 Wear chemical safety goggles and a knee length (41-42 inch) laboratory white coat at all times while in the laboratory when anyone is conducting experiments
2 Wear closed shoes at all times while in the laboratory
3 Wear nitrile gloves when directed to do so by your instructor and/or lab manual
4 Confine long hair when in the laboratory so that it will not catch on fire or encounter chemicals.
Behavioral Rules for Safety
a Do not enter the laboratory until your lab instructor is present b Do not eat, drink, chew gum or smoke in the laboratory at any time Keep all food and drinks sealed and, in your backpack, or purse c Consider all chemicals to be hazardous unless instructed otherwise d Do not taste anything in the chemistry laboratory e Smell chemicals carefully and only when instructed to do so Waft odors towards your nose rather than sniffing directly f Do not use flammable liquids near open flames Most organic liquids are flammable Diethyl ether is especially dangerous g When heating substances in a test tube, never point the mouth of the test tube at yourself or at anyone else It may erupt like a geyser h Do not force glass tubing or thermometers into rubber stoppers The tubing or thermometer may break and cut you badly Consult with your laboratory instructor for assistance i Use caution when handling Bunsen burners, hot plates, and glassware or other equipment that has been heated Burns are the most common laboratory injury so treat all equipment as if it were hot during experiments that involve heating j Work with dangerous or volatile chemicals in a fume hood as directed by your instructor and/or lab manual k Do not perform unauthorized experiments If you see someone else doing something you think may be dangerous, tell him or her to stop and/or report the incident to your lab instructor If another student tells you to stop doing something because it is unsafe, stop as directed Consult your lab instructor if there is a problem or difference of opinion.
Handling Accidents
a Notify your lab instructor immediately if you have an accident, spill, or are injured in any way b If chemicals encounter your skin or eyes, wash with water for at least 15 minutes c Know where to find and how to use the eyewash stations in the lab It is not recommended to wear contact lenses in the laboratory since chemicals splashed in the eye may get under the lens therefore be difficult to rinse If a splash occurs while you are wearing contact lenses, they must be safely removed as quickly as possible d Know where to find and how to use the safety shower in the front of the room e Clean up spilled chemicals immediately Consult your laboratory instructor if you are not sure what to do f Solid sodium bicarbonate (baking soda) is available in the laboratories in containers located by the sinks Use this to neutralize acid spills before wiping them up Similarly, solid citric acid solution is available in containers by the sinks and should be used to neutralize base spills before wiping them up A saturated solution of sodium bicarbonate is also available by the sinks and can be used to wipe dried acid or base residue off lab benches as needed However, if acid or base spills on your skin, do not waste time looking for these neutralizing substances Rinse with water immediately for at least 15 minutes.
Proper Waste Disposal
Separate waste as follows: a Waste chemicals should be disposed of as directed by your lab instructor Most chemicals are NOT to be thrown down the sink Special waste receptacles will be provided for these chemicals Waste chemicals must be sorted by kind, not just mixed with other, different waste chemicals Read waste container labels carefully Notify your instructor when a waste bottle is nearly full Do not overfill waste bottles b Broken glass is to be disposed of in the cardboard boxes labeled "Broken Glass Only" located near the doors to the lab A dustpan and broom are in each lab to assist you in cleaning up broken glass Do not put broken glass in the regular trash, and do not put anything except broken glass in the broken glass containers! c Gloves used in lab are to be disposed of in the containers labeled “Used Gloves Only” located next to the sinks in each lab d Other trash that is not glass and is not contaminated by hazardous chemicals should be placed in the large waste baskets near the front of the lab room.
Other Information You Should Know
a Material Safety Data Sheets (MSDS) are available for all the chemicals used in this course These sheets give information about the chemical, physical, and physiological properties of chemical substances See your instructor for information about accessing these sheets A shortcut to MSDS websites is available on the site mention in the table of contents They can also be found by entering the name of the chemical and MSDS into Google or any other search engine b Each laboratory experiment involves its own specific hazards Be sure to read your laboratory procedure carefully before arriving for lab and take note of all safety precautions You are responsible for the information provided in the laboratory procedure You must also arrive on time for all laboratory sessions so you will be present to hear the safety information provided by your lab instructor For the safety of all students in the class, students who arrive late to lab will not be allowed to perform the lab experiment that day.
Student Safety Training Record
Department Chemistry Laboratory Student Safety Training Record
I certify that I have read the online available following documents from the Chemistry
Department, and that I agree to abide by the policies therein:
2 Emergency Procedures for chemistry lab Classes
3 Instructions for the Safe Use and Care of Chemistry Laboratory Goggles, Coats
S.No Enrol No Name of
Do you wear contact lenses under your goggles?
This information may be needed in case of an emergency yes no yes no yes no
Purpose
This Chemical Hygiene Plan (CHP) sets forth policies, procedures, equipment, personal protective equipment and work practices that are capable of protecting employees and students from the health hazards presented by hazardous chemicals used in laboratories This Plan is intended to meet the requirements of Occupational Exposure to Hazardous Chemicals in Laboratories
Scope
This plan applies to our Chemistry Laboratory where employees work with substances in containers that are easily and safely manipulated by one person The objective of this program is to provide guidance to all laboratory personnel who use chemicals, so that they can perform their work safely
Laboratory Employees Each individual working in a laboratory should be informed about hazards associated with that laboratory and the specific work going on there This includes all faculty, laboratory staff and student workers
Support Personnel Storeroom, janitorial, maintenance, and delivery personnel may be exposed to potential physical and chemical hazards from work carried out in the laboratory They must be informed about the risks involved and trained how to avoid potential hazards
Department Head, Faculty members, Lab instructors, Lab attendants shall:
1 Work with administrators, faculty and laboratory staff to develop and implement appropriate chemical hygiene policies and practices
2 Monitor procurement and use of chemicals in the lab, determining that laboratory facilities and training levels are adequate for chemicals in use
3 Perform regular, formal chemical hygiene and housekeeping inspections that include inspections of emergency equipment
4 Maintain a current chemical inventory of chemicals present within the lab and stored room
5 Review and improve the Chemical Hygiene Plan on, at a minimum, an annual basis
6 Maintain overall responsibility for the safe operation of the laboratories
7 Determine the proper level of personal protective equipment; ensure that such protective equipment is available and in working order
Ensure that the appropriate training has been provided to employees
8 Monitor the waste disposal program.
Standard Operating Procedures for Laboratory Chemicals
The decision to procure a new chemical shall be made by the appropriate Department Head who will ensure a commitment to safe handling and use of the chemical from initial receipt to ultimate disposal
Department of Chemistry is continually and aggressively evaluated current inventory and properly dispose of unnecessary materials
Requests for procurement of new chemicals (i.e., those not currently included in a department’s chemical inventory – this does not apply to re-orders of substances already in use) shall be submitted to the appropriate Department Head for approval
A requisition form shall be used for this purpose Chemicals used in the laboratory shall be those that are appropriate for the ventilation system All chemicals must be received in the chemistry storage room Personnel who receive chemicals shipments shall be knowledgeable of the proper procedures for receipt
Chemical containers shall not be accepted without accompanying labels, material safety data sheets (MSDS) All chemical shipments should be dated when received and opened
The storage area shall be well illuminated, with storage maintained at or below eye level Flammables will be stowed in the designated flammable storage cabinets in lab prep areas
Chemicals must be segregated by hazard classification and compatibility in a well- identified area, with good general exhaust ventilation
Mineral acids should be segregated from flammable and combustible materials Acid resistant trays shall be placed under bottles of mineral acids Nitric acid will be stored in an acid cabinet Acid sensitive materials, such as cyanides and sulfides, shall be separated from acids and protected from contact with acids and water Highly toxic chemicals or other chemicals whose containers have been compromised shall be stored in unbreakable secondary containers The storage area shall NOT be used as a preparation or repackaging area The storage area shall be accessible during normal working hours
Stored chemicals shall be examined at least annually by the Lab instructors for container integrity and/or deterioration The inspection should determine whether any corrosion, deterioration, or damage has occurred to the storage facility as a result of leaking chemicals
The Lab instructors shall conduct periodic inventories of chemicals outside the storage area Unneeded items shall be properly discarded or returned to the storage area
The common method of storing the chemicals in alphabetical order sometimes results in incompatible shelved materials For example, storing strong oxidizing materials next to organic chemicals can present a hazard
A possible solution is to separate chemicals into their organic and inorganic families and then to further divide the materials into related and compatible families Below is a list of compatible families
2 Acetates, Halides, Iodides, Sulfates, Sulfites, Halogens, Thiosulfates, Phosphates
3 Amides, Nitrates (except Ammonium Nitrate), Nitrites, Azides
5 Sulfides, Selenides, Phosphides, Carbides, Nitrides
6 Bromates, Perchlorates, Perchloric Acid, Chlorites, Hypochlorites, Peroxides,
9 Acids (except Nitric) Store acids in a designated cabinet *Nitric Acid is isolated and stored by itself
10.Sulfur, Phosphorus, Arsenic, Phosphorus Pentoxide
2 Alcohols, Glycols, Amines, Amides, Imines, Imides
4 Esters, Ketones, Ketenes, Halogenated Hydrocarbons, Ethylene Oxide
2 No top shelf chemical storage
3 No reactive liquid chemicals stored above eye level
4 Shelf assemblies are firmly secured to walls Avoid island shelf assemblies
5 Provide anti-roll-off lips on all shelves
6 Ideally shelving assemblies would be of wood construction
7 Avoid metal, adjustable shelf supports and clips Better to use fixed, wooden supports
8 Store acids in dedicated acid cabinet(s) Store nitric acid in that same cabinet ONLY if isolated from other acids Store both inorganic and some organic acids in the acid cabinet
9 Store flammables in a dedicated and ventilated flammables cabinet
10.Store severe poisons in a dedicated poisons cabinet
11.Segregate known or suspect carcinogens from other chemicals
12.If you store volatile materials (ether, hydrocarbons, etc in a refrigerator, the refrigerator must be explosion-proof The thermostat switch or light switch in a standard refrigerator may spark and ignite volatile vapors in the refrigerator.)
Each laboratory employee (with training, education, and resources provided by supervision) shall develop work habits consistent with requirements of the Department of Chemistry CHP to minimize personal and coworker potential exposure to chemicals Based on the realization that all chemicals inherently present hazards in certain conditions, exposure to all chemicals shall be minimized
General precautions that shall be followed for the handling and use of all chemicals are:
1 The amount of chemicals at the lab bench shall be as small as practical
2 Skin contact with hazardous chemicals shall be avoided at all times
3 Employees shall wash all areas of exposed skin prior to leaving the laboratory Soap is provided at each sink
4 Mouth suction is prohibited for pipetting or starting a siphon
5 Eating, drinking, smoking, chewing gum, or application of cosmetics in the laboratories prohibited
6 Storage of food or beverages is not allowed in storage areas or refrigerators used for laboratory operations
7 All chemicals and equipment shall be properly labeled, in accordance with
Department of Chemistry CHP guidelines
8 Any chemical mixture shall be assumed to be as toxic as its most toxic component
9 Substances of unknown toxicity shall be assumed to be toxic
10.Laboratory employees shall be familiar with the symptoms of exposure for the chemicals that they work with and the precautions necessary to prevent exposure
11.All laboratory employees shall adhere to the CHP
12.Specific precautions based on the toxicological characteristics of individual chemicals shall be implemented as deemed necessary by the CHP
Each employee shall keep the work area clean and organized At the completion of each workday or operation, the work area shall be thoroughly cleaned, and all equipment cleaned and stowed In addition, the following procedures shall apply to the use of laboratory equipment: a All laboratory equipment shall be used only for its intended purpose b All glassware will be handled and stored with care to minimize breakage; all broken glassware will be immediately disposed of in the broken glass container c All evacuated glass apparatus shall be shielded to contain chemicals and glass fragments should implosion occur Heavy-walled filtration flasks connected to aspirators or house vacuum lines are excepted d Labels shall be attached to all chemical containers, identifying the contents and related hazards e Waste receptacles shall be clearly labeled f All laboratory equipment shall be inspected on a periodic basis and replaced or repaired as necessary g Engineering controls and safety equipment in the laboratory shall be utilized and inspected in accordance with guidelines established in the CHP h The appropriate Laboratory Technician shall maintain an inspection log that documents monthly eyewash/shower testing and flushing A sticker indicating the date of last flushing shall be placed on each shower or eyewash station i The appropriate Laboratory Technician shall visually inspect fire extinguishers monthly A log of the date of the last visual inspection shall be posted by each extinguisher Regular maintenance of fire extinguishers is the responsibility of SMC‟s Facilities Department
F Personal Protective Equipment a Safety goggles are required for employees and visitors to the Chemistry laboratories and will be worn at all times when chemicals are being used in the laboratory b The wearing of contact lenses in the laboratory is strongly discouraged c Chemical goggles and/or a full-face shield shall be worn during chemical transfer and handling operations as procedures dictate d Lab coats should be worn in the laboratory e Appropriate chemical-resistant gloves shall be worn at all times when there exists the potential for skin contact with hazardous chemicals f Used or contaminated gloves are to be disposed of in the special glove disposal containers in each lab Contaminated gloves must not be worn outside of the laboratory Thermal resistant gloves shall be worn for operations involving the handling of heated materials and exothermic reaction vessels
1 Department Head must ensure that each employee knows and follows laboratory- specific rules and procedures established by this plan Faculty must ensure that enrolled students receive appropriate instruction in laboratory safety polices
2 All employees shall remain vigilant to unsafe practices and conditions in the laboratory and shall immediately report such practices and/or conditions to the Department Head The Head must PROMPTLY correct unsafe practices or conditions
3 Long hair or loose-fitting clothing shall be confined close to the body to avoid contact with chemicals or being caught in moving machine/equipment parts
4 Avoid unnecessary exposure to hazardous chemicals by any route Do not smell or taste any laboratory chemicals
5 Encourage safe work practices in coworkers by setting the proper example Horseplay is strictly forbidden
6 Seek information and advice from knowledgeable persons regarding Standards and Codes about hazards present in the laboratory and plan operations, equipment, and protective measures accordingly
7 Use engineering controls (fume hoods, safety shields and general ventilation) in accordance with CHP procedures
1 All containers in the laboratory shall be labeled This includes chemical containers and waste containers The labels shall be informative and durable, and at a minimum, will identify contents, source, date of acquisition, and indication of hazard
2 Portable containers shall be labeled by the individual using the container Exemptions for labeling requirements shall be made for chemical transfers from a labeled container into a container that is intended only for the immediate use of the employee who performed the transfer.
Criteria for Implementation of Control Measures
A When to use fume hoods
Hoods should be used WHENEVER POSSIBLE to contain and exhaust toxic, offensive, or flammable materials Processes that have potential for generating hazardous airborne chemical concentrations must be carried out within a fume hood
B When to use personal protective equipment
Eye Protection - Safety goggles must be worn by all personnel in the laboratory whenever hazardous chemicals are in use NO EXCEPTIONS
Gloves - Gloves should be worn to protect the skin from chemical and physical (e.g heat, cold) exposures Used or contaminated gloves are to be disposed of in the special glove disposal containers in each lab Contaminated gloves must not be worn outside of the laboratory Thermal resistant gloves shall be worn for operations involving the handling of heated materials and exothermic reaction vessels Thermal resistant gloves shall be non-asbestos and shall be replaced when damaged or deteriorated
Laboratory Coats – Knee-length white laboratory coats are to be worn by all employees and students while working with laboratory chemicals.
When to institute special work practices
The Department Head must approve special work practices If particularly hazardous chemicals are to be used (e.g., carcinogens, reproductive toxins, teratogens, or acutely toxic chemicals), standard operating procedures for the use of these substances must be developed and followed.
Fume Hood Management
A Frequency and type of monitoring - all local exhaust hoods used for primary containment control will be monitored for adequate airflow annually The survey will be completed with a calibrated velometer
B Acceptable operating range - Minimum face velocities of at least 100 linear fpm must be maintained for each hood
C Maintenance schedule - Maintenance of local exhausts or fume hoods will be completed on an "as needed" basis, or annually, whichever comes first.
Employee Information and Training
Employees will be provided with training to ensure that they are apprised of the hazards of chemicals present in their work area Such training will be provided at the time of an employee's initial assignment to a work area where hazardous chemicals are present and prior to assignments involving new exposure situations.
Procedures to secure medical consultation and examination are as follows
a Seek immediate medical care at IIMSR b Report exposure to instructor, faculty member or Department Head c The following information will be provided to the physician d Identity of hazardous chemical e Description of conditions under which exposure occurred f Description of signs and symptoms employee is experiencing g Copy of MSDS h A written opinion from the physician shall be provided to the employer including: i Recommendation for further medical follow-up j Results of medical exam and tests k Any medical condition revealed during the exam that places the employee at increased risk l A statement that the employee has been informed by the physician of the results of the exam and any medical condition that may require further treatment or examination.
Emergency Response/Chemical Spills
a When spills of hazardous chemical occur within the Laboratory, the following procedures are followed to prevent injury or property loss: b Provide any first aid (if necessary) to affected individuals Liberally use eyewash station and/or safety shower to flush affected areas for AT LEAST 15 minutes A large exposure to the body merits ambulatory service c Notify HOD of spill d Evacuate the area e Always refer to MSDS for special precautions or spill cleanup requirements f If spilled materials exhibit flammability, eliminate ignition sources such as hot plates, Bunsen burners, etc., if this can be done safely g Avoid all contact with spilled material If necessary, use protective gloves, gown, goggles, and/or respirator h Neutralize acids and bases i Contain collected materials and label container with name of contents and also as Hazardous Waste
Liquid Spills a Confine spill to as small an area as practical b For small quantities of acids or bases, use the neutralizing agent from the chemical spill clean- up kit An absorbent material specially prepared for acid/base spills may also be used c For small quantities of other materials, such as organic solvents, utilize an absorbent material to clean-up spill Examples of absorbent materials are vermiculite, dry sand, paper towels, etc d For large quantities of inorganic acids and bases, flush with large amounts of water, preferably toward a containment area *CAUTION must be taken not to add too much water to create a flood that may react with water-reactive materials and cause spattering and additional personnel exposure e If possible, with small manageable spills, utilize spilled containment material (kitty litter, sand, or booms) found in the emergency spill kits located throughout the Science Departments Large quantity spills will be handled by professional hazardous waste personnel or the fire department f Carefully pick up and decontaminate any bottles, broken glass, and/or other containers Decontaminate over the bucket or pail to collect contaminated wash g Avoid using any shop vacuum that is not rated for chemical clean up A potential exists for atomizing hazardous wastes and creating a potential human inhalation exposure h If the spill is extremely volatile (high vapor pressure), allow the spill to evaporate and exhaust out the laboratory exhaust (e.g., fume hood) i Properly contain, label, store and/or dispose of collected hazardous waste (See waste disposal section for methods)
Sweep solid spill of low toxicity into a designated, easily decontaminated, dustpan and place in a labeled container for disposal
Mercury - Clean up with a mercury spill clean-up kit Collect elemental mercury in a sealed container to prevent exposure to mercury vapors In the event of large spills or spills that render some mercury unavailable for clean-up (e.g., mercury in floor cracks or beneath lab benches), an airborne evaluation of mercury vapor content may be required
Any compressed gas cylinders used in science laboratories must be secured with two chains, top and bottom, always when in use and stored In addition, all cylinders must be properly labeled Regulators must not be left attached to unused cylinders for extended periods of time
An incident investigation should take place after each spill and/or accident The Incident Report should be completed by concerned instructor and faculty member and forwarded to the HOD.
Review and Update
This Chemical Hygiene Plan will be reviewed and updated annually
Instructions for the Safe Use and Care of Chemistry Laboratory Coats, Goggles & Gloves
1 Purchase a pair of chemical safety goggles)
2 Bring your goggles with you for all laboratory sessions of your chemistry class You will not be allowed to work in the lab without your goggles
3 Wear your goggles when anyone in the lab is conducting an experiment
1 Purchase a lab coat that fits you well Lab coats that are too tight or too loose are not safe Sleeves that are too long should be rolled up
2 If your lab coat has not been contaminated with a hazardous substance, you may wash it as you do your other clothing
3 If your lab coat becomes contaminated with a hazardous substance, as with any other lab spill, notify your instructor immediately
4 Contaminated lab coats will be handled by your instructor as they deem appropriate
Nitrile Gloves: a Nitrile gloves are to be worn only during portions of experiments where specified by the experimental procedure, when instructed by the instructor or supervisor, or when working with substances for which the protocol requires the use of gloves b Note that nitrile gloves are flammable and will stick to your skin if they burn Do not wear gloves while working with Bunsen burners c Do not wear gloves outside the lab d When a chemical encounter a glove, remove the glove immediately and place it in the glove waste e Do not touch surfaces such as doorknobs, computer keyboards, and chairs while wearing gloves f Gloves with holes or tears must be removed immediately and disposed of properly g Dispose of gloves at the end of each experiment in the glove waste containers provided in each lab
4 MSDS SHEETS ONLINE: http://hazard.com/msds/
Below are photos and names of common lab equipment you will encounter in Chemistry lab listed in alphabetical order
Balance (electronic) Beakers Bunsen Burner Burette
Clay Triangle Crucible Crucible in Triangle Crucible Tongs
Dropper Pipets Dropper in action
Pinch Clamp Pipets and Bulbs
Plastic and Rubber Policemen Ring Clamp & Stand
Scoopula Stirring Rods Thermometers Test Tubes in Rack
Test Tube Holder Tube & Holder in
Wash Bottle Watch Glasses Wire Gauze
An additional site to view lab equipment, including techniques for using it, may be found at: http://www.dartmouth.edu/~chemlab/techniques/ph.html
Following materials are required to perform the experiments in the chemistry lab
• Safety Goggles: Chemical splash goggles are required for all laboratory experiments Safety goggles must fit snugly to your face and be able to fit over your prescription eye wear
• Laboratory Coat: A knee length (41-42 inch) laboratory white coat must be worn at all times while in the laboratory when anyone is conducting experiments
• Closed Shoes: Wear closed shoes at all times while in the laboratory
• Nitrile Gloves: Nitrile gloves must be worn when directed to do so by your instructor and/or by the lab manual
• Scientific Calculator: This calculator should preferably be equipped with log, ln, exp and 1/x functions
• Lab Notebook: Purchase one notebook for recording the experiments that you will perform
7 INSTRUCTION FOR LAB RECORD WRITING
• Write on the right-hand page the following order: a Serial number and date of performance (in the margin) b Name and number of the experiment as given in the list c Aim of the experiment d Description of the apparatus e Procedure including sources of error and precautions taken to eliminate or to minimize them f Inference or Result g Explanation, if necessary, of any divergence in the expected result
• Left hand page should contain the following in their proper places a Neat diagram of the main apparatus b Observation in tabular form c Calculation in tabular form d Graph sheets and other papers to be attached e Students should submit a record of the previous experiments when they come for practical work f An experiment is deemed to be complete when it is satisfactorily performed and recorded
8 BASIC CONCEPTS OF VOLUMETRIC ANALYSIS
Chemical analysis of the compounds is carried out in two ways
Qualitative analysis shows what element a given contains Quantities analysis determines the quantity of a particular component present in substance It is carried out in two ways
Gravimetric analysis involves the estimation of the amount of a given compound from the results of weighing Volumetric analysis is based on the measuring the volume of the solution of a substance
Terms involved in volumetric analysis:
1 Titration: The process of finding out the volume of one of the solution required to react completely with a definite volume of one the other solution of known concentration is called titration
2 Titrant: The solution of known strength is called titrant
3 Titrate: The solution whose concentration to be estimated
4 Indicator: The reagent which indicates the endpoint or equivalent point of the titration The strength of concentration of a solution is expressed in the following ways
NORMALITY: Number of gram equivalents of the substance dissolved per liter of the solution is called Normality It is denoted by N Normality = Wsolute/Esolute × 1/Vsovent (in lit) Where E is Gram equivalent weight
MOLARITY: Number of grams moles of a solute dissolved per liter of solution is called
Molarity It is denoted by M
Molarity = Wsolute/Msolute × 1/Vsovent (in lit) Where M is Gram molecular weight
MOLALITY: It is the number of moles of the substance dissolved in 1kg of the solvent it is denoted by (m)
Molality = Wsolute/Msolute × 1/Wsovent (in kg)
1 Close packing geometry in solid Solid structure
2 Preparation of Laboratory solutions Preparation techniques
3 Limit test for Chloride & sulfates Inorganic for testing
4 Preparation of coordination compound [Ni(NH3)6]2 Coordination compound
5 Purification of Kitchen Salt by re-crystallization method Crystallization technique
Tris(oxalate)ferrate(III) trihydrate Coordination compound
7 The Mechanism of Aquation of trans- dichlorobis(1,2-diaminoethane) cobalt(III) chloride Coordination compound
8 Preparation of potassium-Chromium alum,
9 Preparation of potassium-Aluminum alum,
EXPERIMENT 1 Close packing geometry in solid
The main purpose of this activity is to study close packing geometry, i.e., to illustrate the structure of ionic solid
Ionic solid can be viewed as a close packing of metal atoms The arrangement of atoms, molecules, or ions in a regularly and repeatedly pattern is known as a lattice space The arrangement’s nature is determined by three factors:
1 Relative shape and size of atom, molecule or ion
2 Nature and relative strength of chemical bonding
3 Thermal energy of the system
Two applied models of the arrangement are hole filling model (balls represent atoms or ions that are packed close one to others) and ball and stick expanding model, where the balls are separated by the stick connectors In ball and stick crystal structure model, stick connectors represent covalent bonds (such as bonds in diamond) or ionic bonds (such as bonds in NaCl) On the other hand, stick connector illustrate crystal lattice of a solid
In this activity, you must arrange the balls, observe and fill the observation data on your work sheet to understand close packing geometry in solid
• Ping-pong balls (at least contain of two colors)
Use amount of ping-pong and other smaller balls to arrange various arrangement patterns and to complete the following tasks
1 Arrange the balls in side-by-side arrangement (Figure 1a) and in closest arrangement (Figure 1b)
Figure 1.1 Packing models of (a) side-by-side layer, (b) hexagon layer, (c) simple cubic layer, (d) body centered cubic
Determine the maximum number of balls that can touch another one ball (center- ball) in the same layer for each arrangement
Answer: ……… balls for (a) and balls for (b)
Determine which is the closer packing, (a) or (b)
In this case, geometry structure in (a) is not a close packing, whereas (b) is a close packing The packing (b) often called as hexagon layer (pay attention to the hexagon layer illustrated by dots)
2 If we add the second, third layer, and so on, to the arrangement model (a) so that the balls of second and third layer lie above the first layer, we get the packing pattern of layer A, A, A
Determine the number of balls that touch another ball in layer A, A, A Answer: balls
The numeric is called as coordination number (number of balls, atoms, ions that touch one center-ball, atom or ion) To get this geometry structure, can be represented by two layers: A, A, where each layer contains four balls What geometry is resulted? (See Figure 1c)
3 If the hole between the two A, A layers filled by one more ball (in the same size) so that the filled-ball touch all other balls, the two layers will expand The resulted geometry from those expanding is called
(Figure 1d) which has coordination number:
Determine which is the closer packing, (c) or (d)
The two resulted-geometry structures from the expanding of (a) model are not a close packing or closest packing, because these arrangements still can be changed to be a closer one
Hexagon and cubic close packing
Two possibilities arrangement of closest packing of same size balls are hexagon closest packing (HCP) and cubic closest packing (CCP) The last arrangement also called as face centered cubic closest packing (FCC) Both arrangements use the hexagon layer (Figure 1b) and represent the most effective way to arrange balls to fill the hole/space optimally To simplify, one layer represented by 3-balls or 7-balls pattern
To observe hexagon closest packing (hcp), firstly, put the 3-balls-triangular pattern (layer A) on the desk Secondly, put the 7-balls–hexagon pattern (layer B) above it so that the balls fit into the hole of layer A Finally put another 3-balls-triangular pattern so that the fit into fill the hole of layer B and lie above of those layer A (Figure 2a) The expanding of this pattern produces the hexagon closest packing geometry (hcp) The hexagon closest packing follows the pattern of A, B, , , ,
Note: the first layer always called as layer A The second layer is called layer B if the balls fit into the hole or do not lie above to those in layer A The third layer is called layer
C if the balls fit into the hole to those in layer B and do not live above to those in layer A Determine the maximum balls that touch the center-ball in the hcp pattern
Answer: ……… balls, consists of ……… balls in the same layer and
……… balls in above and under those layers This numeric called as coordination number
Analogically, arrange another hcp pattern by using 7-balls–hexagon, 3-balls- triangular and 7-balls-hexagon layers Firstly, put the7-balls-hexagon layer on the desk (layer A) Secondly, put the 3-balls-triangular layer (layer B) above it so that the balls fit into the hole of layer A Finally put another 7-balls–hexagon layer so that the balls fit into the holes of layer B and lie above of layer A’s balls (Figure 2b)
Determine the coordination number of this pattern
Is the coordination number of this pattern still the same with the previous one?
(a) (b) (c) (d) (e) Figure 1.2 Various possibilities of closest packing
Repeat the packing models of hcp, at least, consists of three layers, where each layer consists of 7-balls-hexagon layer Put one ball as center-ball, and then count other balls that touch it (Figure 2c) Determine the coordination number of this pattern
Hold this hcp packing pattern and direct it to the light source Pay attention to the route of the light on the hcp packing What do you get?
Alternatively, put the hcp packing on the desk and put the wire through the hcp packing via the holes among the balls Pay attention to the route of the wire in the hole of hcp packing What do you get?
To observe the cubic closest packing (CCP) or face centered cubic (FCC), arrange the hcp packing (Figure 2d) Hold the 3-balls-triangular layer on the top and turn it 60 o clockwise Now, the balls in the 3-balls-triangular layer on the top do not lie above to those in the first layer (the 3-balls-triangular layer at the bottom) but fit into the holes The expanding of this pattern yield to the face centered cubic closest packing or face centered cubic (FCC) The FCC follows the pattern of A, B, , , ,
Determine the maximum balls that touch the centered ball in the FCC pattern
Answer: ……… balls, consists of ……… balls in the same layer and
……… balls in above and under those layers This numeric called as coordination number
Analogically, arrange the FCC pattern with three layers of 7-balls–hexagon layer (Figure 2e)
Determine the coordination number of this pattern Answer: ………
Is the coordination number of this pattern still the same with the previous one? Answer: (Yes / No) *
Hold this FCC packing pattern and direct it to the light source Pay attention to the route of the light on the FCC packing What do you get?
Alternatively, put the FCC packing on the desk and put the wire through the fcc packing via the holes among the balls Pay attention to the route of the wire in the hole of fcc packing What do you get?
EXPERIMENT 2 Preparation of laboratory solutions
Preparing solutions is one of the most fundamental tasks performed in the laboratory Two skills that are essential to a chemist are preparing solutions of known molarity and diluting solutions of known molarity to solutions of new, less concentrated molarities Molarity is defined as the number of moles of solute per liter of solution (denoted M) Molarity usually describes solutions of accurate concentration, where the molecular weight of the solute is known Solutes are weighed on an analytical balance, and volumes are measured in volumetric flasks
Preparation of a solution by dissolving a solid solute in the solvent m solute (g) = M solute (g/mol) x n solute (mol/L) x V solute (L)
• m solute : Weight of solute needed for the preparation
• M solute : Formula mass of the solute
• n solute : Molarity of the solution
• V solute : Volume of the solution
• C 1 : The concentration of the starting (stock) solution
• V 1 : The volume of starting (stock) solution needed to make the dilution
• C 2 : The desired concentration of final (dilute) solution
• V 2 : The desired volume of final (dilute) solution
• V 2 : The desired volume of final (dilute) solution
• V 1 : The volume of more concentrated solution that is mixed with solvent to make a more dilute solution
After completing this practical, students should be able to:
• Define and correctly use the following terms: solute, solvent, solution, aqueous solution, concentration, mole, molar, formula weight, dilution series, parallel dilution, and serial dilution
• Prepare a solution of specified volume and concentration from separate solute and solvent
• Prepare a solution of specified volume and concentration by diluting a stock solution
• Prepare a dilution series using both the parallel and serial dilution methods; and be able to determine which method is most appropriate for preparing a given dilution series
PART A: Preparation of KMnO 4 solution
I Preparation of 250 mL of 0.01M KMnO 4 solution
1 Calculate the weight of KMnO4 needed to prepare 250 mL of a 0.01 M solution
2 Weigh out the calculated weight of KMnO4 using an analytical balance and a small weigh boat
NOTE: Free-flowing solids are removed from stock bottles by slowly pouring from the bottle or its lid into the weigh boat Small quantities are best transferred by first pouring some of the solid into the lid of the stock bottle, then pouring from the lid into the weigh boat Any excess can be poured from the lid back into the stock bottle To avoid contamination, never place any objects into a stock bottle and never pour chemicals from the weigh boat or another container back into a stock bottle
3 Pour approximately 150 mL of deionized water (DW) into a clean 250-mL beaker, estimating the volume from the calibration marks on the side of the beaker
4 Slowly pour the weighed KMnO4 into the beaker and stir well with a stirring rod until the KMnO4 is completely dissolved To transfer any KMnO4 left behind on the weigh boat into the beaker, use a plastic squeeze bottle of DW
5 Once the solute is completely dissolved, transfer the solution to a 250-mL volumetric flask
6 Transfer 40 or 50 mL of DW from a plastic squeeze bottle into the beaker, forcing the water all around the inside of the beaker to rinse any remaining solution to the bottom Swirl the liquid for a few seconds, and then pour it into the volumetric flask containing the KMnO4 solution
7 Rinse the beaker again with a few milliliters of DW and pour the liquid into the volumetric flask Repeat, if necessary, in order to transfer all of the solute to the volumetric flask but be careful that the total volume of your solution does not exceed 250 mL
8 Use the squeeze bottle or a medicine dropper to slowly add enough DW to the volumetric flask in order to bring the total volume of solution to 250 mL
9 Mix the solution thoroughly by stoppering the flask securely and inverting it three to five times
10.Attach a piece of marking tape to the volumetric flask With a permanent marking pen, write the concentration and composition of the solution on the tape (i.e 0.01
II Preparation of 50 ml of 2 mM KMnO 4 solution using 0.01M KMnO 4 solution:
1 Calculate the volume of 0.01 M KMnO4 solution that should be diluted in order to make 50 mL of a 2 mM KMnO4 solution
2 Using an appropriate measuring device, transfer the required solution into a 50- mL volumetric flask
3 Add enough DW to the volumetric flask to bring the total volume to 50 mL Mix the solution thoroughly by stoppering the flask securely and inverting it three to five times
4 Attach a piece of marking tape to the volumetric flask With a permanent marking pen, write the concentration and composition of the solution on the tape (i.e., 2 mM KMnO4)
III Preparation of several solutions using the parallel dilution from 0.01M KMnO 4 solution
1 Calculate the amount of 0.01M KMnO4 solution and the amount of DW needed to make 10 mL each of the following solutions: 1.0 mM KMnO4, 0.6 mM KMnO4, 0.4 mM KMnO4, 0.2 mM KMnO4and 100 μM KMnO 4
2 Use tape to label five 20-mL test tubes with the final concentrations of the solutions being prepared, and then place the tubes in a test tube rack
3 To make your first solution, use an appropriate measuring device to transfer the required amount of 0.01M KMnO4 solution into a 10 mL volumetric flask
4 Add enough DW to the volumetric flask to bring the total volume to 10 mL and pour into the test tube
5 Clean your 10-mL volumetric flask with DW and prepare the rest of the dilutions in the same way
IV Prepare several solutions using the serial dilution technique
1 Starting with your solution of 2 mM KMnO4, you will make 6 mL of each of the following concentrations of KMnO4: 1.0 mM, 0.5 mM, 250 μM, 125 μM, and
2 Label the arrows in the diagram below to show how you would make the required solutions Above each vertical arrow, write down the volume and type of liquid you will place in the tube Below each horizontal arrow, write down how much solution you will transfer from one tube to the next:
3 Now, use tape to label your test tubes–the first tube with the molarity of your stock solution and the remaining tubes with the final concentrations of the dilutions being prepared Place the tubes in a test tube rack
⇒ NOTE: The letters below correspond to the letters on the arrows in the diagram above
A Place the correct amount of 2 mM KMnO 4 (V1 + V2) into tube 1 and use parallel dilution to bring the solution to the correct concentration
B Using an appropriate measuring device, place the correct amount of solvent into all other tubes IMPORTANT: When making a dilution series, make sure you use a clean measuring device each time you transfer a solution with a different solute concentration
C Transfer the correct amount of solution (V1) from tube 2 to tube 3 and then thoroughly mix the contents of tube 3 with a Vortex mixer
D Transfer the correct amount of solution (V1) from tube 3 to tube 4 and then thoroughly mix the contents of tube 4 with a Vortex mixer
E Transfer the correct amount of solution (V1) from tube 4 to tube 5 and then thoroughly mix the contents of tube 5 with a Vortex mixer
F Transfer the correct amount of solution (V1) from tube 5 to tube 6 and then thoroughly mix the contents of tube 2 with a Vortex mixer
G Remove the correct amount of solution (V1) from tube 6 and discard it
5 Finally, place the tubes with your serial dilutions into a separate test tube rack in order of decreasing concentration and label the rack “serial dilutions.”
PART B: Preparation/Testing of 0.10 M Copper sulfate pentahydrate
1 Find the mass in grams needed to make 50 mL of 0.10 M CuSO4.5H2O solution using a 50-mL volumetric flask Record
2 Weigh the mass of solute calculated from Step 2 and carefully transfer the blue solid to a clean 50-mL volumetric flask
3 Add about two thirds the volume of distilled water needed and swirl the flask When most of the solid has dissolved add the rest of the water stopping below the mark on the flask To add the remaining water, use the squeeze bottle or a medicine dropper Insert the stopper and invert the flask a few times for uniform mixing NOTE: The bottom of the curved water surface, the “meniscus”, should touch the mark on the neck
4 Test to see if the concentration of your blue copper sulfate solution is correct by measuring its absorbance at a given wavelength Fill a cuvette with your solution and place in the spectrometer which is set to a wavelength of 700 nm Record the absorbance, (A), which is directly related to concentration
(Preparation/Testing of 0.10 M Copper sulfate pentahydrate)
Mass (g) of CuSO4.5H2O needed to prepare 50 mL 0.10 M solution:
2 Molar mass of CuSO4.5H2O 250 g/mol
3 Mass in grams needed (1 x 2) = moles x molar mass g
Absorbance at 700 nm, 0.10 M CuSO4.5H2O, known: 0.77
Absorbance at 700 nm, 0.10 M CuSO4.5H2O, measured:
EXPERIMENT 3 Limit test for chloride & sulfates
The limit test for chlorides is provided to demonstrate that the content of chlorides does not exceed the limit given in the individual monograph in terms of micrograms of chloride ions per gram of the substance being tested The standard solution against which the comparison of opalescence is made contains 250 μg of
• To identify impurities in the given sample
• To observe the opalescence in the given sample
• To compare the opalescence of test solution with standard solution
Carry out the test in matched flat-bottomed comparison tubes of transparent glass of about 70 mL capacity and about 23 mm internal diameter bearing a 45-mL and a 50-mL mark Nessler cylinders complying with the above dimensions are suitable The expression "matched tubes" means tubes that are matched as closely as possible in internal diameter and in all other respects Prepare the test sample and standard as follows:
Specific weight (1 g of sample A) of compound is dissolved in water or solution is prepared as directed in the pharmacopoeia and transferred in Nessler cylinder
Take 1ml of 0.05845 % W/V solution of sodium chloride in Nessler cylinder
Add 1ml of nitric acid Add 1ml of nitric acid
Dilute to 50ml in Nessler cylinder Dilute to 50ml in Nessler cylinder
Add 1ml of AgNO3 solution Add 1ml of AgNO3 solution
Keep aside for 5 min Keep aside for 5 min
Observe the Opalescence/Turbidity Observe the Opalescence/Turbidity
NOTE: Nitric acid is added in the limit test of chloride to make solution acidic and helps silver chloride precipitate to make solution turbid at the end of process
The opalescence produce in sample solution should not be greater than standard solution If opalescence produces in sample solution is less than the standard solution, the sample will pass the limit test of chloride and vice versa
The limit test for sulfates is provided to demonstrate that the content of sulfates does not exceed the limit given in the individual monograph in terms of micrograms of sulfates per gram of the substance being tested Limit test of sulfate is based on the reaction of soluble sulfate with barium chloride in presence of dilute hydrochloric acid to form barium sulfate which appears as solid particles (turbidity) in the solution
• To identify impurities in the given sample
• To observe the opalescence in the given sample
• To compare the opalescence of test solution with standard solution
Carry out the test in matched flat-bottomed comparison tubes of transparent glass of about 70 mL capacity and about 23 mm internal diameter bearing a 45-mL and a 50-mL mark Nessler cylinders complying with the above dimensions are suitable The expression "matched tubes" means tubes that are matched as closely as possible in internal diameter and in all other respects Prepare the test sample and standard as follows:
Specific weight (2 g of sample A) of compound is dissolved in water or solution is prepared as directed in the pharmacopoeia and transferred in Nessler cylinder
Take 1ml of 0.1089 % W/V solution of potassium sulphate in Nessler cylinder
Add 2ml of dilute hydrochloric acid Add 2ml of dilute hydrochloric acid Dilute to 45 ml in Nessler cylinder Dilute to 45 ml in Nessler cylinder
Add 5ml of barium sulphate reagent Add 5ml of barium sulphate reagent
Keep aside for 5 min Keep aside for 5 min
Observe the Turbidity Observe the Turbidity
NOTE: Barium sulfate reagent contains barium chloride, sulfate free alcohol and small amount of potassium sulfate Hydrochloric acid helps to make solution acidic
Alcohol prevents supersaturation and potassium sulfate increases sensitivity of the test by giving ionic concentration in the reagent which just exceeds the solubility product of barium sulfate
The turbidity produce in sample solution should not be greater than standard solution If turbidity produces in sample solution is less than the standard solution, the sample will pass the limit test of sulfate and vice versa.
EXPERIMENT 4 Preparation of coordination compound, [Ni(NH 3 ) 6 ]I 2
To study the preparation of coordination compound of [Ni(NH3)6]I2
Complex (coordination) compound is characteristic compound of transition metals that correspond to the existence of d orbital The existence of d orbital cause transition metals not only have various oxidation states but also the capability to interact coordinately with another atom donor Complex compound of [Ni(NH3)6]I2 is an example of Ni 2+ compound with coordination number 6 where its crystallization is relatively easy to be studied The success of the compound preparation is easily tested qualitatively to Ni 2+
Graduated cylinder 10 mL Nickel chloride hexahydrate
Labeled-test tube Potassium iodide
1 Dissolve 1 g of nickel chloride hexahydrate into 5 mL water a beaker glass
2 Place that beaker glass in the fume hood and add 10 mL of concentrated NH3 solution (~25%)
3 Add 2.6 g of potassium iodide to the mixture Let the mixture for several minutes
4 Collect the formed crystal on Hirsch funnel, wash it twice with 2 mL of ethanol solution 1:1 and then add 2 mL of ethanol solution
5 Dry the crystals in windy air for several minutes
6 Move the dried crystals to filter paper Ask the assistant how to move crystals from Hirsch funnel to filter paper
7 Move out the exceeding solvent by press the crystals between two filter papers
8 Move the resulted crystal to the weighed and labeled tube Weigh the tube mass with the contents Calculate mass percentage of the product based on the amount of nickel chloride hexahydrate
9 Test the existence of nickel ion in the compound
Dissolve a small amount of sample (about 0.001 g of compound in 0.5 mL of water), add
5 M NH3 solution, and then add 5 drops of dimethylglyoxime solution Red strawberry solid produced if there is Ni 2+ ion
10 Test the existence of iodide ion in the compound
Dissolve a small amount of compound (about 0.001 g of compound in 0.5 mL of water), acidify with 2 drops of 5 M sulfuric acid solution and then add 3% H2O2 solution.
EXPERIMENT 5 Purification of kitchen salt by re-crystallization method
To study the crystallization method on the purification of kitchen salt by evaporation and precipitation
Resulting purity high-level compound is an important thing in chemistry The usual method on solid purification is re-crystallization (the forming of repeating crystal) Re- crystallization based on the difference of solubility capacity of solid and impurities in particular solvent If it possible, use alternate solvent that only dissolve the impurities Such purification is widely used in industrial and laboratory to improve the quality of particular substance
Requisites of a solvent in re-crystallization process are:
1 Give significant solubility differences between purified-substance and impurities
2 The solubility of substance in solvent is a temperature function The solubility usually decreases with the decreasing of temperature
3 Easily separate from the crystals
4 Do not leave the impurities in the purified crystals
5 Do not react with purified substance
Kitchen salt contains sodium chloride as major component, and Ca 2+ , Mg 2+ , Al 3+ , Fe 3+ ,
SO4 2-, I - and Br - as impurities Those impurities easily dissolved in water Re-crystallization method with water as a solvent is general method to get high-level sodium chloride from kitchen salt Particular ions needed to eliminate the existence of impurity ions These ions will bind the impurity ions to form low-level solubility compound in water By this, the purified and impurities substances easily separated
Burner Kitchen salt and CaO crystal
Beaker glass Dilute Ba(OH)2 or BaCl2 (0,5 M) solution Graduated cylinder (NH4)2CO3 solution (6 gram in 200 mL)
Filter paper and litmus paper
1 Into a beaker glass, dissolve about 16 g kitchen salt in 50 mL water Boil and stir the mixture Divide the solution into 2 parts in equal amount and called as solution A and
2 Crystallization of solution A a Add about 0.2 g of CaO into solution A b Add Ba(OH)2 solution drop to drop until no more precipitate formed at the last drop c Add (NH4)2CO3 solution drop to drop and stir continuously d Filter the mixture into cleaned and weighed beaker glass Neutralize filtrate by adding of dilute HCl solution drop to drop (Test the neutrality of the solution with litmus paper in every drop) e Evaporate the solution until relatively dry f Weigh the resulted NaCl (which is brighter and whiter than original kitchen salt) and calculate the percentage
3 Crystallization of solution B a Saturate the solution B by HCl gas adding Hydrochloric acid gas obtained from the reaction of kitchen salt and concentrated sulfuric acid (Do the reaction in fume hood) The flowing of HCl stopped when no more NaCl crystal growing in the solution b Separate the crystal by filtering, dry it and then weigh the product and compare to method 1 above
9.6 EXPERIMENT 6 THE PREPARATION OF POTASSIUM
TRIS(OXALATO)FERRATE(III) TRIHYDRATE
Mark the level of 45 cm3 water in a 250 cm3 beaker To a well-stirred solution of 5 g of ferrous ammonium sulfate in 20 cm3 of warm water containing 1 cm3 of dilute sulfuric acid in the beaker, add a solution of 2.5 g of oxalic acid dihydrate in 25 cm3 of water Slowly heat the mixture to boiling (beware of bumping) then allow the yellow precipitate to settle Decant the supernatant through a Buchner funnel making sure it has a properly fitted filter paper Add 15 cm3 of hot water to the solid, stir and filter Drain well and then transfer all the precipitate from the paper back into the beaker with 10 cm3 hot water
Add 3.5 g solid potassium oxalate monohydrate and heat to approximately 40 °C Add slowly, using a dropper, 9 cm3 of "20 vol" hydrogen peroxide (If the precipitate looks yellowish, not brown and settles readily, decant the supernatant, add a solution of 0.2 - 0.4 g potassium oxalate monohydrate in 1 - 2 cm3 water and then hydrogen peroxide dropwise until the precipitate dissolves Then add the previously decanted supernatant) Heat to boiling and add a solution of 2 g of oxalic acid dihydrate in 30 cm3 of water in portions, add 20 cm3 initially, then if the brown precipitate still remains, add more solution little by little until it all dissolves Boil the clear solution down to a volume of 40 - to 50 cm3, filter through a Buchner funnel with well-fitting paper and add 95% ethanol slowly until a precipitate starts to form (~30 cm3) Redissolve any crystals by heating
(beware of fire) and leave to crystalline
Filter and wash the crystals on the Buchner with a 1:1 ethanol / water mixture and finally with acetone, (beware fire again) Dry in the air and weigh The complex is photosensitive and should not be exposed to light unnecessarily Store in a sample bottle wrapped in foil
Determination of the oxalate content of Potassium [trisoxalatoferrate(III) trihydrate]
The iron(III) complex is first decomposed in hot acid solution and the free oxalic acid is titrated against standard (0.02 M) potassium permanganate solution No indicator is required
In duplicate, weigh accurately about 0.2 g of the potassium [trisoxalatoferrate(III)] complex previously prepared Boil the sample with 50 cm3 of 1 M sulfuric acid in a conical flask Allow the solution to cool to about 60°C and titrate slowly with the potassium permanganate solution provided (which you will need to standardize)
Continue until the warm solution retains a slight pink coloration after standing for about
Calculate the percentage by weight of oxalate in the complex, compare this with the theoretical value and thus obtain the percentage purity of the complex
Photochemical reactions of Potassium trisoxalatoferrate(III) trihydrate
Prepare duplicate solutions containing 0.2 g accurately weighed of your sample in 15 cm3 of dilute sulfuric acid Dilute the solutions to 50 cm3 with distilled water and expose them to sunlight for one hour (note carefully what happens) Titrate with your standardised permanganate to determine the amount of reducing agent present
Expose a small portion of your product to sunlight for several hours Make sure that the crystals have been ground to a fine powder and that you periodically stir the crystals so that all the sample gets exposed equally to the sunlight Perform the following tests on samples of both irradiated and unirradiated complex:
Dissolve your sample in dilute sulfuric acid and divide the solution into three
1 Treat with a freshly prepared solution of potassium ferrocyanide
2 Treat with a freshly prepared solution of potassium ferricyanide
3 treat with a solution of potassium thiocyanate
9.7 EXPERIMENT 7 THE MECHANISM OF AQUATION OF TRANS-
DICHLOROBIS(1,2-DIAMINOETHANE) COBALT(III) CHLORIDE
Coordination complexes of cobalt(III) undergo ligand exchange or substitutions slowly as compared to many other transition metal compounds Their slow reactions have made them suitable for kinetic investigations of their reaction mechanisms The present experiment involves a kinetic study of the acid hydrolysis of trans-[CoCl2(en)2]Cl, whereby the probable mechanism of the octahedral cobalt(III) substitution can be determined The reaction will be conducted such that each student will investigate one of the following variations: pH, temperature, concentration and ionic strength The entire class will collate these results which can be used to show the effect of these variations on the aquation
Complexes of this type undergo aquation in a stepwise fashion according to the equations: trans-[CoCl2(en)2]+ + H2O → trans-[CoCl(en)2(H2O)]2+ + Cl- trans-[CoCl(en)2(H2O)]2+ + H2O → [Co(en)2(H2O)2]3+ + Cl- where the first step is the one to be measured quantitatively in this experiment
In principle, two fundamentally different mechanisms are possible for these reactions, a dissociative or associative mechanism The kinetic rate laws expeected for these two types of mechanism are: dissociative: Rate = k1[complex] associative: Rate = k2[complex][H2O] = kobs[complex] that is, they are dependent only on the concentration of the complex and are first order This observation, however, furnishes no information as to the role played by the water and does not give any information about the molecularity of these reactions
Nevertheless, the way in which the rate constant is affected by various changes in the nature of the complex ion is expected to give us information about the mechanism It has been found that increasing chelation such as replacing two NH3 ligands by one ethylenediamine slows down the rate of acid hydrolysis Allowing for the chelation effect the divalent monochloride complexes react about 100 times slower than the univalent dichloride complexes trans -[CoCl2(en)2]Cl
Preparation of trans -[CoCl2(en)2]Cl
CoCl2.6H2O (2 g) is dissolved in 2 cm3 of water in a beaker and 1 cm3 of 1,2- diaminoethane (en) in 5 cm3 of water is slowly added cautiously and with stirring The solution is cooled in an ice bath to 5°C and 2 cm3 of H2O2 (30%) is slowly added while maintaining the temperature at 5°C [ CAUTION: Keep H 2 O 2 off the skin and eyes!]
Then the solution is gently warmed to about 60-70°C for 15-20 minutes