CHEM261 Pratical Manual 2012

Applied Inorganic Chemistry for Chemical Engineers CHEM261 2012 ‐ 1st Semester LABORATORY MANUAL Student name: _____________________________
Student number: _____________________________
SCHOOL OF CHEMISTRY AND PHYSICS HOWARD COLLEGE CAMPUS UNIVERSITY OF KWAZULU‐NATAL I, the undersigned (please print your full name): _____________________________________________________________________ Student No.: ____________________ do hereby acknowledge having read and understood the documents headed “Occupational Health and Safety” and “Laboratory Rules and Regulations”. Furthermore, I accept that contravention of these rules and regulations may lead to my expulsion from the laboratory class, or classes, with subsequent loss of my Duly Performed (DP) certificate. I agree to abide by any additional laboratory regulations or safety rules presented in writing in this laboratory manual or issued verbally by the lecturer‐in‐charge, or other responsible member of staff, during pre‐laboratory lectures or in the laboratory. In addition, I understand that I must attend at least 80% of the scheduled laboratory classes and that failure to do so, irrespective of the reasons, may result in the loss of my DP certificate. DATE: __________________ SIGNATURE: ___________________________ It is a legal requirement that SAFETY GLASSES, LABORATORY COATS AND CLOSED SHOES are worn in the laboratory at ALL times. 
Sunglasses (normal or prescription) are NOT to be worn as a substitute for safety glasses. 
Prescription glasses (except sunglasses) are acceptable PROVIDED THEY COVER THE EYES COMPLETELY. 
Some types of contact lens should not be worn in the laboratory. Check with your lens supplier. 
All shoes MUST be closed. No high heels are allowed. 
The School requires students to REMOVE, or to MAKE SAFE, headgear that is considered dangerous or a potential hazard. 
The School requires students with long hair to tie it back. i General Fire Orders Fire‐fighting instructions are exhibited in each laboratory, but the following orders must always be obeyed. In the event of a fire Attack it at once using the appropriate fire fighting equipment and SHOUT for help. On hearing a fire evacuation alarm Stop normal work immediately. Make safe any apparatus and material in use, shutting off any local gas taps/valves, electricity and other potentially dangerous services under your control. Immediately leave the building. Go to the Fire Evacuation Area outside the main entrance to the building; unless you have been given any other instructions.
ii Occupational Health and Safety (OHS) YOU are warned that all substances handled and all operations performed in a laboratory can be hazardous or potentially hazardous. All substances must be handled with care and disposed of according to laid down procedures. All operations and manipulations must be carried out in an organised and attentive manner. In order to assist you in developing good and safe laboratory techniques, a set of Laboratory Rules and Regulations is attached. You are required to read these and acknowledge that you have read and understood them. Additionally, in the laboratory manuals and/or pre‐practical lectures your attention will be drawn to the correct and safe handling of specific chemicals/reagents/solvents and to the correct/safe manner in which specified laboratory operations must be carried out. These specific instructions and/or warnings must never be ignored. iii Laboratory Rules and Regulations  Students must be present before the start of each scheduled practical session. Latecomers will be refused entry to the laboratory.  No student will be permitted to work in the laboratory outside of practical hours.  Do not put anything into your mouth while working in the laboratory. NEVER taste a chemical or solution. Eating and drinking is PROHIBITED in all laboratories.  All students are required to wear a laboratory coat. No student will be permitted to work in a laboratory without one.  All students who do not wear conventional spectacles must wear eye protection. These must be worn throughout all practical sessions  All students must wear closed shoes while in the laboratory.  All students must have a laboratory towel to dry apparatus and clean bench‐tops.  No entry is allowed into preparation and issue rooms.  Apparatus and chemicals are not to be removed from the laboratory.  Students will find the laboratory benches clean on arrival in the laboratory. The bench at which you work must be left clean when you leave the laboratory at the end of the practical session. Bench tops must be wiped clean. Glassware and other apparatus should be left clean and dry, unless otherwise indicated or instructed. Sinks and basins must be cleaned after each practical.  Work areas must at all times be kept clean and free from chemicals and apparatus that are not required. All glassware and equipment must be returned to its proper place, clean and dry and in working condition, unless otherwise indicated or instructed. iv  All solids must be discarded into the bins provided in the laboratory. Never throw matches, paper, or any insoluble chemicals into the sinks. Solutions and chemicals that are emptied into sinks must be washed down with water to avoid corrosion of the plumbing. Waste solvents must be placed into the special waste solvent bottles provided.  Before leaving the laboratory at the end of the practical session, make sure that all electrical equipment is switched off, and that all gas and water taps are shut off.  Students who break or lose equipment allocated to them will be required to pay for replacements. All breakages or losses must be reported to the technician in charge.  Do NOT heat graduated cylinders or bottles.  Any apparatus or glassware, which has to be heated, must be heated gently at first, with heating gradually increased thereafter.  Balances must be treated with care and kept clean and tidy at all times.  Fume‐hoods must be used when handling toxic and fuming chemicals. Other operations, such as ignitions, are also carried out in fume‐hoods. The only parts of the body that should ever be in the fume‐hood are the hands ‐ never put your head inside a fume‐hood!  Never leave a laboratory experiment unattended!!  Reagent bottles must be re‐stoppered immediately after use. It is ABSOLUTELY FORBIDDEN to introduce anything into reagent bottles ‐ not even Pasteur pipettes! Solutions and reagents taken from bottles must NEVER be returned to the bottles. Do not place the stopper of a reagent bottle onto an unprotected bench top.  Laboratory reagents and chemicals must be returned to their correct places immediately after use. Spillage must be cleaned off bottles/containers. v  Liquids ‐ whether corrosive or not ‐ must be handled with care and spillage on the bench or floor should be avoided. Any spillage should be cleaned up at once. If the liquid is corrosive (acids or bases), call your demonstrator or staff member in charge. Never hold a container above eye level when pouring a liquid.  When carrying out a reaction, or boiling a liquid in a test tube, point the mouth of the test tube away from yourself and others in the laboratory.  Beware of hot glass and metal. Never handle any item that has been in a flame, hot oven, or a furnace without taking precautions. Use leather/asbestos gloves/tongs, or ask for advice.  Report all accidents, cuts, burns, etc., HOWEVER MINOR, to your demonstrator or the staff member in charge. Eyewash stations are located in various places in the laboratory. Ensure that you know where the nearest one to your bench is located.  A chemical laboratory is not a place for horseplay. Do not attempt any unauthorised experiments. Do not play practical jokes on your classmates ‐ transgressors will be banned from the laboratory, with consequent refusal of a Duly Performed (DP) Certificate. vi Instructions to Students Read the following instructions CAREFULLY. Make sure you understand the instructions and sign the declaration at the front of the manual.  Fire Extinguishers are provided in the laboratory. Make sure you know where they are situated and how to use them. N.B. A SHOWER is also located in the laboratory. Make sure you know where it is!  Gas is highly flammable. It can form dangerous explosive mixtures with air when not controlled. GAS TAPS MUST BE TURNED OFF WHEN GAS IS NOT IN USE. Slow leaks can lead to dangerous concentrations.  Burners: Students must provide their own matches or lighters. The use of paper is FORBIDDEN as it poses a fire hazard.  Flammable solvents such as ether, alcohol, hexane, benzene, acetone, etc., are used in the laboratory. Students must take care when handling these solvents. The following rules are important:  Flammable solvents are NOT TO BE HEATED IN OPEN CONTAINERS OVER A FLAME. These should be heated over a steam bath or under reflux conditions.  Solvents, such as chloroform, hexane, ether, which are immiscible with water must be disposed of by carefully pouring them into the WASTE SOLVENT bottles located in the fume cupboards. They may NOT be poured down sinks or troughs.  Solvents that are miscible with water (e.g.alcohol and acetone) may be poured into the sinks, provided they are washed away with an ample volume of water.  Glassware with ground glass joints is expensive and must be treated with care. After use, glassware must be carefully cleaned, dried, and ground surfaces must be lightly smeared with petroleum jelly. This prevents the “freezing together" of the joints. The process of "freezing" is accelerated by the presence of any alkaline solid or solution left on the surfaces. The joints should NEVER be forced or heated with a flame. Disassemble ALL joints before leaving the laboratory. vii  Students must be careful when using balances. ALL SPILLAGES MUST BE CLEANED UP and balances must be left clean.  Laboratory benches must be looked after. Acid spillages must be neutralised with sodium bicarbonate and cleaned up immediately. Bunsen burners, hot glassware and steam baths must be placed on asbestos mats.  Refuse Bins are for SOLIDS only. No burning or smouldering materials may be placed in bins.  Sinks and troughs are for liquids only. Solid material will cause blockage of the drainage system.  Use of Fume Cupboards: The careless use of certain chemicals makes working in the laboratory extremely unpleasant. Bromination must be done in the fume cupboard. Always check warnings on the reagent bottles BEFORE using.  Practical Preparation: Before the practical class you are required to:  Familiarise yourself with the experimental procedures you are about to perform.  Read up the relevant section in your textbook.  Fill in specific information, as requested.  Reactions will be discussed in lectures, practical work being examinable in your examination.  All SOLID products prepared and derivatives of unknowns must be submitted in neatly labelled sample tubes. Liquid products may not be handed in, but must be shown to your demonstrator for verification and then poured into the appropriate bottle on the demonstration bench.  Report write‐ups must be done on an A4 notebook.  Report for a particular practical MUST be handed in at the conclusion of that practical session. Alternatively,at an agreed time by your lecturer, and they will then be marked and returned to you at the start of the following laboratory session. viii Schedule of Practical Work Practical Practical 1A: Practical 1B: Topic Preparation of the “double salt” ammonium copper sulfate Preparation of the “coordination complex” tetraamine‐
copper(II) sulfate Page No. 1 1 Practical 2: Preparation of [Co(NO2)6]3‐ 2 Practical 3: Preparation of [Co(acac)3] 3 Practical 4: Preparation of copper(I) chloride 4 Practical 5: Preparation of chromium metal by the Thermite Reaction 5 Practical 6: Construction of model crystals 6 Practical 1A
Preparation of the “double salt” ammonium copper sulfate Procedure: Dissolve copper(ii) sulfate pentahydrate (2 g) and ammonium sulfate (1 g) in 5 mL cold water and heat while stirring on hotplate until it completely dissolved. Cool the solution at room temperature, and filter the crystals at the pump. Dry between pad of filter paper and paper towel. Evaporate (heat) the filtrate to about half of it volume then cool under tap water. Dip a glass rod to facilitate the formation of crystals. Filter and dry the second crop of crystals. Record the total weight of product but keep the two samples separate. Calculate the yield as a percentage. Practical 1B
Preparation of the “coordination complex” tetraamine‐copper(II) sulfate Procedure: Dissolve 4 g of copper(ii) sulfatepentahydrate in 10 mL of 60% ammonia solution (6 mL concentrated ammonia and 4 mL deionised water). Cool the resulting deep‐blue solution in ice, stirring continuously while 15 mL of alcohol is added drop‐wise using dropper. Allow the mixture to stand at least overnight or latest by Friday morning (before 12.00 pm). The supernatant liquid should be almost colourless. Filter the crystalline product; wash it with 10 mL of 50% ethanol ammonium solution. Dry the salt in air and calculate the percentage yield. NB: 
In hot water the salt solution remains saturated hence the need to heat the cold water to dissolve the salts completely. 
You also need to show your samples to the demonstrator for marking purpose. 
Solutions, reagents and waste management during and after the practicalis expected from students. 1 Practical 2
Preparation of [Co(NO2)6]3 Procedure: Heat 12 g of pure potassium‐free sodium nitrite in 12 mL of cold water using hot plate until it completely dissolved. Cool the solution to 50 oC, and dissolve 4 g of cobalt nitrate hexahydrate in the liquid. With the aid of a dropper, add 4 mL of 50% acetic acid dropwise while continuous stirring. Transfers the dark brown solutions into a test tube provided then slowly slide it down into the filter flask and attach the aeration tube. Draw a steady stream of air through the solution for 20 minutes to remove excess oxides of nitrogen, some product may crystallize out during aeration. Place the liquid and any solid that has formed (the more vigorous the air current the more material tends to settle out) in a beaker surrounded by ice bath. Add 20 mL of 95% ethanol slowly with agitation, and allow the mixture to crystallize in the cold for 20 minutes. Filter the orange‐brown product by suction and discard the mother liquor into the waste bottle. Wash the material three times with 10 mL of crude ethanol or until the final wash is almost colourless. Dry the crystals in air. Calculate the percentage yield. NB: 
Solubility of sodium nitrite in water 89 g/100 mL at 20 oC, thus 12 g should be soluble in 12 mL of water above 65 oC. 
Use 100 mL beaker to dissolve sodium nitrite. 
The vacuum tap should be open very slowly. 
Show your product to your demonstratorfor marking purpose. 
Solutions, reagents and waste management during and after the practical. 2 Practical 3
Preparation of [Co(acac)3] Procedure: Slurry 2.5 g powdered cobalt(II) carbonate and 20 mL acetylacetone in a 125 mL Erlenmeyer flask. Heat the mixture to 100C on a hot plate. Transfer the flask immediately onto a white tile and add 15 mL of 10% H2O2 at a rate of 2 mL/min while stirring. Reheat the reaction mixture to incipient boiling, and then add 15 mL more of H2O2 as before. After addition is complete, heat to boiling. Cool the mixture in an ice‐salt bath for half an hour and filter the green‐black sludge with suction. Wash with water followed by small (3 x 5 mL) amounts of cold ethanol. The yield should be about 6 g of raw product. Recrystallize from toluene(≈20 mL), let it cool at room temperature and filter by gravity and dry at 110C. The yield of purified dark green crystals is expected to be 4.0 to 4.5 g pure. Calculate the percentage yield. NB: 
Show your product to your demonstratorfor marking purpose. 3 Practical 4
Preparation of Copper(I) chloride Procedure: Copper(I) chloride is prepared by reducing copper(II) ions with sulfur dioxide or sulfite ions in the presence of chloride ions. The copper(I) ions once formed, react with chloride ions to form the insoluble copper(I) chloride. Prepare three solutions: (a) Dissolve sodium sulfite (3.3 g) in 50 mL of water. (b) Dissolve copper(II) chloride (4.8 g) in 25 mL of water. (c) Prepare a sulfurous acid solution by dissolving sodium sulfite (1 g) in 10 mL of water and add 12 mL of 2 M hydrochloric acid. Add slowly, with constant stirring, the sodium sulfite solution to the copper(II) chloride solution. Dilute the suspension of copper(I) chloride so formed with about half the sulfurous acid solution, allow the precipitate to settle, and decant most of the supernatant solution. Filter the solid by suction on a sintered glass disc and then wash the precipitate on to the sinter with thesulfurous acid solution. Take care that the copper(I) chloride is always covered by a layer of solution. Finally wash the product with portions of glacial acetic acid, alcohol, and ether. Dry the product in a warm oven. Calculate the percentage yield. NB: 
Show your product to your demonstratorfor marking purpose. 
Copper(I) chloride is slowly oxidized by moist air to give the basic copper(II) chloride, CuCl2.3Cu(OH)2, so it must be stored in stoppered containers. 4 Practical5
Preparation of chromium metal by the Thermite Reaction 2Al + Cr2O3 = Al2O3 + 2Cr Procedure: Fuse potassium dichromate (1 g) in a porcelain crucible. Cool, and grind to a fine powder. Ignite hydrated chromium(III) oxide (4 g), (note that the bottle may be labelled chromic hydroxide), in a porcelain crucible until the green anhydrous chromium(III) oxide is obtained. Prepare a mixture containing chromium(III) oxide (2 g), fused potassium dichromate (0.5 g), and aluminium powder (1 g). The reaction will proceed without the potassium dichromate but the temperature may not be sufficiently high to fuse the chromium metal produced. This makes recovery more difficult. Fill a crucible (4 cm x 7 cm o.d.) to within 1 cm of the rim with powdered calcium fluoride, and make an indentation about 2 cm in depth in the centre of the powder with the end of a boiling tube. Place the prepared mixture in this indentation in the calcium fluoride. Prepare an ignition charge of barium peroxide (1 g) and aluminium powder (0.1 g) and place this on the surface of the reaction mixture. Insert a short length of magnesium ribbon into the ignition charge to act as a fuse. Place the crucible in a fumecupboard,surround it vertically on four sides with asbestos board and fasten another asbestos board horizontally above the asbestos ‘walls’. During the firing of the charge wear safety goggles or a facemask. Ignite the magnesium ribbon using a micro burner. There will be some sparking initially but this will quickly cease and the charge will continue to react quite smoothly. Allow the product to cool, and carefully transfer it to a mortar. Grind the product and remove the bead (or beads) of chromium metal. Weigh the chromium and calculate the yield. 5 Practical 6
Construction of model crystals (written by Prof M Laing) This laboratory exercise is derived from those used in the Department of Chemistry, Purdue University, USA for Course 115 (Profs Robinson and Bodner) and 241 (Prof Davenport). You are given a model consisting of 5 sheets of transparent plastic each of which has drilled in it 25 holes. The coordinates of the sheets in fractions of z are: 0, 1/4, 1/2, 3/4, 4/4 and within the z sheets, the coordinates of theholes in the fractions of x are: 0, 1/4, 1/2, 3/4, 4/4 and in fractions of y are: 0, 1/4, 1/2, 3/4, 4/4 The x, y coordinates of the hole marked ‘*’ are:x =3/4, y = 1/4; its z = 4/4. The coordinates for the positions of the spheres will be given as number of quarters: with x being given before y, followed by z. The coordinates of the hole marked ‘*’ thus are: 3,1,4. Models of crystal structures are made by placing Styrofoam spheres at the appropriate positions in the framework. 6 Student Name:_________________________________ Student Number:
Simple cubic Place atoms at: z = 4 : 0.0; 4.0; 0.4; 4.4 z = 0 : 0.0; 4.0; 0.4; 4.4 (a) What fraction of the atom at the corner of the cell (0, 0, 0) is within the unit cell? _______________ (b) How many unit cells share the atom at the corner (0, 0, 0)? _______________ (c) How many atoms are there per unit cell? _______________ (d) How many atoms are in contact with an atom at (0, 0, 0)? _______________ (e) If the atoms are in contact along the cell edges, what is the relationship between the length of the cell edge (ao) and the radius (r) of the atom? ________________ (f) Given that the volume of the atom is 4/3r3 and the volume of the cell is ao3, calculate what fraction of the unit cell volume is occupied by the atoms. ________________ 7 2. Body‐centred cubic Place atoms at: z = 4 : 0.0; 0.4; 4.0; 4.4 z = 2 : 2.2 z = 0 : 0.0; 0.4; 4.0; 4.4 (a) What fraction of the atom at (1/2,1/2,1/2) is within the cell? _______________ (b) What fraction of the atom at (0, 0, 0) = (1, 1, 1) is within the cell? _______________ (c) How many atoms are there per unit cell? _______________ (d) How many atoms are in contact with the atom at (1/2, 1/2, 1/2)? _______________ (e) The atoms at (0, 0, 0), (1/2, 1/2, 1/2), (1, 1, 1) are in contact along the body diagonal, b; i.e. b = 4r. Calculate the volume of the cell in terms of r. _______________ (f) What fraction of the unit cell is occupied by atoms? _______________ (This structure is adopted by pure iron at room temperature, and by brass of composition CuZn at 300C when all the Cu and Zn atoms are scrambled between (0, 0, 0) and (1/2, 1/2, 1/2). 8 3. Face‐centred cubic Place white atoms at: z = 4 : 0.0; 0.4; 4.0; 4.4; 2.2 z = 2 : 0.2; 2.0; 4.2; 2.4 z = 0 : 0.0; 0.4; 4.0; 4.4; 2.2 (a) What fraction of the atom at the centre of the face is within the cell? ________________ (b) What is the net number of atoms per face‐centred cubic unit cell? ________________ (c) What is the coordination number of an atom in this face centred cubic unit cell? ________________ (d) The atoms are in contact along the face diagonal, d, of the unit cell, i.e. d = 4r.What is the value of ao, the unit cell edge, in terms of r? ________________ (e) What is the volume of the unit cell in terms of r? ________________ (f) What is the volume of the cell occupied by atoms (in terms of r)? ________________ (g) What fraction of the unit cell volume is occupied by the atoms? (many metals have this structure) 9 ________________ 4. Diamond (FCC) Retain the FCC structure from part 3; add white atoms at: z = 3 : 3.1; 1.3 z = 1 : 1.1; 3.3 These atoms are now in the diamond structure. (a) How many atoms are there per unit cell? ________________ (b) The atom at (0, 0, 0) is covalent bonded to the atom at (1/4,1/4, 1/4), with C  C = 1.54 Å (equal to 1/4 of the body diagonal). Calculate ao, the unit cell edge. ______________Å _______________ (c) What is the coordination number of each atom? (Silicon, germanium and tin (below 0C), have this structure). N.B. Retain this model for part 5. 10 5. Zinc sulfide : blende Replace all the white atoms at z = 3, and z = 1 by red atoms. This is the cubic zinc blende (ZnS) structure. (a) What is the coordination number of the atom at (1/4, 1/4, 1/4)? (b) What is the coordination number of the atom at (0, 0, 0)? ________________ ________________ (c) Assume the Zn atom is at (1/4, 1/4, 1/4) and the S atom is at (0, 0, 0); (i) how many S atoms are there per unit cell? ________________ (ii) how many Zn atoms are there per unit cell? 11 ________________ 6. Sodium chloride (NaCl) Remove the red atoms from the layers z = 1 and z = 3. The standard FCC array remains. Now add red spheres at the following positions. z = 4 : 0.2; 2.0; 2.4; 4.2 z = 2 : 0.0; 0.4; 4.0; 4.4; 2.2 z = 0 : 0.2; 2.0; 2.4; 4.2 The pattern is the sodium chloride structure, face‐centred cubic. Assume that the red spheres are Na+, and that the white spheres are Cl. (a) How many Cl are in contact with each Na+? ________________ (b) How many Na+ are in contact with each Cl? ________________ (c) How many Clare there per unit cell? ________________ (d) How many Na+ are there per unit cell? ________________ (e) Calculate the shortest distance between each pair of Cl ions in terms of the cell edge ao. ________________ (f) Assume all the white spheres (Cl) are in contact, i.e. the face diagonal is 4 x r. What is the radius, R, of the cation in terms of r if it just touches the six anions arranged around it in an octahedron? 12 ________________ 7. Caesium chloride structure, CsCl, primitive cubic Clear all spheres from the model. Place one red sphere at : z = 2 : 2.2; and 8 white spheres at z = 0 : 0.0; 0.4; 4.0; 4.4 z = 4 : 0.0; 0.4; 4.0; 4.4 Note: There are two types of atom. (a) How many red atoms are there per unit cell? ________________ ________________ (b) How many white atoms are there per unit cell? Compare this with the BCC structure. In this CsCl structure, the atom at (1/2, 1/2, 1/2) differs chemically from the atoms at the corners of the cubic cell.(The atoms of brass of composition CuZn take up this ordered arrangement at room temperature.) (c) Assume that the Cl ions are at the corners of the cube and touch along the edges of the cube; i.e. ao = 2r. Assume that the Cs+ at (1/2,1/2,1/2) is in contact with the 8 Cl ions at the corners of the cube. Calculate the ratio i.e. radius of Cs+ ion to radius of Cl ion. ________________ 13 8. Rutile (TiO2) This structure is common for metal oxides of formula MO2. Place red spheres (M4+) at: z = 3 : 0.0; 0.4; 4.0; 4.4 z = 2 : 2.2 z = 1 : 0.0; 0.4; 4.0; 4.4 and white spheres (O2‐) at z = 3 1.1; 3.3 z = 2 3.1; 1.3 z = 1 1.1; 3.3 (a) How many O2‐ are in contact with the M4+ at (1/2,1/2,1/2)? ________________ (b) How many M4+ are in contact with each O2‐ at (3/4, 1/4, 1/2)? 14 ________________ 9. Fluorite (CaF2) Put 14 white spheres into the model to give a FCC arrangement (as per part 3). Now add red spheres at: z = 3 : z = 1 : 1.1; 3.1; 1.3; 3.3 1.1; 3.1; 1.3; 3.3 The white spheres represent Ca2+cations, and the red spheres represent Fanions. (a) How many Ca2+ ions are in contact with each F ion? _______________ (b) How many F ions touch each Ca2+ ion? _______________ (c) How many F ions are there per unit cell? _______________ (d) How many Ca2+ ions are there per unit cell? 15 _______________