Inorganic Chemistry CHEM210 Practical Manual 2014 School of Chemistry and Physics University of KwaZulu‐Natal, Westville Campus CONTENTS Page Safety information 3 Report writing 5 6 The preparation of potassium aluminium sulphate 7 dodecahydrate The preparation of sodium hexanitrocobaltate(III) Practical 3 The preparation of stannic iodide 9 Practical 4 The preparation of bis(ethylenediamine)copper(II) tetraiodo 10 Example of report mark scheme Practical 1 Practical 2 mercurate(II) 8 Practical 5 The preparation of chromium metal 11 Practical 6 Construction of solid state models 13 2 Safety information Safety in the laboratory is of the utmost importance. There will be no compromising in this area. Failure to comply with any of the regulations may result in you being asked to leave the laboratory for that session or depending on the circumstances being withdrawn from the course. If the fire bell rings: 1.
Switch off any heaters (gas or electric). 2.
Leave by nearest Fire Exit or Fire Escape. 3.
Do not obstruct people leaving the building, or firemen entering. 4.
Assemble in front of the main Chemistry door. Laboratory Rules 
Safety glasses or goggles must be worn at all times in the laboratory. Even if you are doing some safe operation, someone else might do something that could affect you. 
Wear a lab coat and tie back long hair. 
Appropriate footwear is essential. (No open toe shoes or high heels). 
Report any accident at once to the demonstrator or lecturer. 
Always keep bags in the locker room. Move about the laboratory with care. Never run. 
No eating or drinking or smoking in the laboratory. 
No unauthorized experiments. 
No unprofessional behaviour, such as shouting, the operation of mobile telephones, etc will not be tolerated. General Safety Precautions 
Read the safety instructions carefully before you come into the laboratory. 
Think about what you are doing at all times. Tell a demonstrator if anything about your experiment seems unusual, or if you have an accident, however trivial it may seem. 3 
Always follow experimental instructions carefully. It is especially important to use a fume cupboard when this is specified, and also to ensure that the fume cupboard is turned on. 
Before you use any chemical, make sure that the name on the bottle is exactly the same as that specified in the instructions. If in doubt, consult a demonstrator. 
Acids and alkalis, particularly if concentrated, should always be treated with the greatest respect. Always add acid to water, never water to concentrated acid. Deal with spills by adding water, and sodium bicarbonate if necessary, and mop up as soon as possible. 
Work in a tidy and organised fashion. Cluttered benches may cause accidents. 
Turn off all equipment when it is not needed. Remember what has just been heated and avoid touching hot glass or metal. 
Put waste chemicals and solvents in clearly marked Waste bottles for safe disposal. Label all samples/bottles correctly and clearly. 
Make sure you know the locations of fire extinguishers, fire blankets, eye wash stations and drench showers, etc. You must be aware of the experiments you are doing and on which particular day. You will get much more out of the session, if you read the manual before you come. If you do not understand something then ask at the beginning. If at any point you do not understand, stop and think, and then if you are still having problems ask an academic or demonstrator. 4 Report Writing A full typed (or written) report by you will be handed in for each of the practicals. These reports must be handed in at the beginning of the following practical session, i.e. you have ONE WEEK to prepare it. Your name, student number, experiment number, title and date must appear as part of the heading. Also it is important that you have your bar code label well stuck on the cover page of your report. Please also note that late report submissions will not be accepted and/or will be penalised. In the practicals which involve synthetic targets, a reaction equation and a diagram of the products’ structure must be shown. The yield and percentage yield must be given in the report. Pay attention to any additional requirements or questions within each of the practicals. It is expected that you will discuss the practicals with other students in the group ‐ but the report must be your own work. Please read carefully the section on plagiarism in the Chem210 Handout and sign it. Any cases of dishonesty will be reported directly to the University Proctor. We are not only teaching you to do chemistry but also to have integrity and faith in your work. 5 Example of report mark scheme Title, date, experiment number, name and number of student, etc. 2 marks 4 marks Introduction (at least half page typed, double spacing) A description, structure, and/or an outline of the chemistry involved Experimental Procedure An understandable outline of the experimental procedure should be used. More importantly this should include deviations from the set operation in the manual and therefore reported has it actually carried out in the laboratory. Hence, you expected to write in past tense, 3rd person and passive voice 4 marks Results A description of all the results, tables, graphs, calculations and theoretical yield and its calculations should be presented. No discussion 4 marks Discussion This should include a discussion of the results. What went wrong, what worked well, etc. 4 marks Conclusion What conclusions can be drawn from the experiment? This is NOT opening a new discussion or rephrasing an old one! 2 marks Reference List (if applicable) If the practical contains questions that need to be addressed, they will also count a certain percentage toward the report. Marks will be deducted for bad/illegible style. NOTE: This just a guide and the actual marking scheme can change from one practical report to another and would we at the desecration of the academic in charge and his demonstrators. 6 Practical 1: The preparation of potassium aluminum sulphate dodecahydrate Chemicals used: Aluminium metal, potassium hydroxide, sulphuric acid and ethanol When aluminium is placed in contact with hot potassium hydroxide, hydrogen is given off. By treating the resulting solution of potassium aluminate with an excess of sulphuric acid, aluminium ions are formed in the hydrated state. The solution thus contains an equal number of potassium and aluminium ions together with an excess of sulphate ions and sulphuric acid; i.e. conditions favourable for the formation of potassium aluminium sulphate dodechydrate, KAl(SO4)2.12H2O, a typical double salt. Procedure: Add aluminum metal foil (1 g) and 1.5 M KOH (50 mL) to a 400 mL beaker. Dissolve the aluminum metal by heating the beaker on a hot plate. A small amount of gray‐black material may remain undissolved due to impurities or other metals alloyed with the aluminum this can be removed by gravity filtration. Allow the solution to cool to room temperature. To this solution slowly add with stirring 6 M, H2SO4 (30 mL). The initial gelatinous precipitate should redissolve when all of the acid has been added. If not, heat the solution gently until it redissolves. When you have completed the above steps, the volume of the solution should be approximately 50 mL. If it is not put the solution back on the hot plate until the volume is reduced to approximately 50 mL. After this, cool the solution in an ice bath for 20 minutes. Crystals should begin to form. Filter the crystals using a Buchner funnel and a suction flask. Wash the crystals on the filter paper with a 50 % aqueous alcohol solution (4 X 5 mL). Allow the crystals to dry. Transfer the crystalline product to a pre‐weighed watch glass. Place the watch glass and its contents in the drying oven. When it has been dried for at least 5 minutes, record the weight of the alum. Calculate the percentage yield. Question 
Give the definition of a double salt. 7 Practical 2: The preparation of sodium hexanitrocobaltate(III) Chemicals used: Sodium nitrite, cobalt nitrate hexahydrate, acetic acid and ethanol Procedure: Dissolve pure potassium‐free sodium nitrite (6 g) in hot water (8 mL) (in a 50ml test tube). After cooling the solution to 50C, dissolve cobalt nitrate hexahydrate (2 g) into the liquid. With continuous stirring using a glass rod, 50% acetic acid (2 mL) is added dropwise from a separating funnel and the dark brown solution is transferred (in the test tube) to a filter flask fitted with a stopper and an inlet tube leading almost to the bottom of the vessel. A steady stream of air is drawn through the solution for twenty minutes to remove excess oxides of nitrogen; some product may crystallize out during the aeration. The liquid and any solid that has formed (the more vigorous the air current the more material tends to settle out) are now placed in a beaker and surrounded by an ice bath. From a dropping funnel 95% alcohol (15 mL) is added slowly with agitation, and the mixture is then allowed to crystallize in the cold for twenty minutes. The orange‐brown product is filtered by suction and the mother liquor is set aside. The material is washed three times with alcohol (5 mL); the final washing should be almost colourless. The crystals are dried in air. Record the yield of your product and calculate the percentage yield. Place the product in a sample bag and label it. Questions 1. What process is happening during the aeration part of the practical procedure? 2. In terms of crystal field theory what type of ligand is NO2? 3. How many unpaired electrons are in the complex? Would you expect the complex to be high spin or low spin? 8 Practical 3: The preparation of stannic iodide Most of the heavier main group (p‐block) elements have the capacity to expand their coordination number beyond that of their “normal” (Lewis structure) covalency by forming complexes with neutral ligands. The triorganophosphines (R3P) family of ligands is capable of allowing the metals and metalloids of group 14 to achieve this “expanded octet” configuration. Chemicals used: Glacial acetic acid, acetic anhydride, tin, iodine and calcium chloride Procedure: Glacial acetic acid (25 mL) and acetic anhydride (25 mL) are placed in an oven‐dried 100 mL round‐bottomed flask. Sheet tin (0.5 g), cut into small pieces, and iodine (2 g) are then added to the solution. A reflux condenser and CaCl2 drying tube are fitted and the contents gently boiled on a sand bath until a vigorous reaction begins. When this subsides, boil the liquid (for at least an hour) until all (or most) of the tin metal has been consumed. This will be difficult to observe as the solution is very dark. The heating is then discontinued, the condenser removed and the hot supernatant liquid carefully (use gloves) decanted into a hot, oven‐dried conical flask. This mixture is allowed to cool, and orange crystals should precipitate. Filter the crystals rapidly by suction. The product is recrystallized by re‐dissolving in a minimum volume (15 – 20 mL) of warm chloroform and then cooling to ice temperature. The recrystallized product is filtered off under suction and allowed to dry. Record the yield and calculate the percentage yield. Questions 1. Why are stannic halides rendered more inert by complexation? 2. Draw the isomeric forms of derivative (Ph3P)2SnI4. Suggest how you might differentiate between the different isomers. 9 Practical 4: The preparation of bis(ethylenediamine) copper(II) tetraiodo‐mercurate(II) This is a comparatively insoluble compound containing a complex cation and complex anion. The two complexes are made separately and then mixed to give the final product. Chemicals used: Mercury(II) chloride, potassium iodide, ethylenediamine and copper (II) sulfate pentahydrate Procedure: Dissolve mercury(II) chloride (0.7 g) in warm water (12 ml). The solution is then cooled and to this is added a 1.0 M potassium iodide solution (10 mL). A orange to red precipitate forms. To dissolve the precipitate add incremental amounts of KI (0.1g at a time). To a solution of copper(II) sulphate pentahydrate (0.5 g in 4 ml of water) ethylenediamine (0.5 mL) is added. A deep violet solution is formed. The two solutions are then mixed by first heating the mercury complex solution to near boiling, and then adding, with stirring, the copper complex solution. On cooling the resultant mixture, fine blue‐violet crystals are deposited. Filter using a Buchner flask, wash the crystals with water (10 mL) and then with a little ethanol. Allow to dry. Record the yield. Calculate the percentage yield. Questions 1. What is the structure of the product? 2. Draw the crystal field theory d–orbital diagram for the copper complex. Place the electrons in the appropriate positions. 10 Practical 5: The preparation of chromium metal Chemicals used: Chromium(II) oxide, potassium dichromate, aluminium powder and calcium fluoride Procedure: Fuse potassium dichromate (1 g) in a porcelain crucible. Cool, and grind to a fine powder. Ignite hydrated chromium (II) 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 completely the chromium metal produced. This makes recovery more difficult. Fill a crucible 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 into 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 fume cupboard, surround it vertically on four sides with fire retardant tiles and fasten another board horizontally above the “walls”. Ignite the magnesium ribbon using a Bunsen burner. There will be some sparking/flaming 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 record the yield. Calculate the percentage yield. Bring your metal product to one of the demonstrators. 11 Questions 1.
Estimate the minimum temperature in the above reaction. 2. Calculate the free energy change for the reaction at 773.15 K, 1273.15 K and 1773.15 K. Consult your 1st Year Chemistry textbook if unsure how this calculation is done. Repeat the calculations for the reactions of aluminum with zirconium(IV) oxide 12 Practical 6: Construction of solid state models This laboratory exercise is derived by Professor M Laing (UKZN) 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 the holes 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 numbers 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. 13 StudentName:_________________________________
StudentNumber: _____________________
6.1 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) or (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? _______________ 14 6.2 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. ________________ 15 6.3. 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? ________________ 16 6.4. Silicon Retain the structure from part 6.3; add white atoms at: z = 1 : 1.1; 3.3 z = 3 : 3.1; 1.3 These atoms are now in the silicon structure at below 0 °C. (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), assume the SiSi bond distance = 1.54 Å (equal to 1/4 of the body diagonal). Calculate ao, the unit cell edge length in Å. ______________ (c) What is the coordination number of each Si atom? N.B. Retain this model for part 6.5. 17 _______________ 6.5 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? 18 ________________ 6.6 Potassium chloride (KCl) 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 K+ ions, and that the white spheres are Cl ions. (a) How many Cl are in contact with each K+? ________________ (b) How many K+ ions are in contact with each Cl ions? ________________ (c) How many Cl ions are there per unit cell? ________________ (d) How many K+ ions 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? ________________ 19 6.7 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? ________________ (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. ________________ 20 6.8. Titanium dioxide ‐ Rutile 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)? ________________ 21 6.9 Fluorspar (Fluorite ‐ CaF2) Put 14 white spheres into the model to give a FCC arrangement. Now add red spheres at: z = 3 : 1.1; 3.1; 1.3; 3.3 z = 1 : 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? _______________
22 SCHOOL OF CHEMISTRY AND PHYSICS WESTVILLE 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: ___________________________ 23