CHEMISTRY PRACTICALS..docx - KAKAMEGA CENTRAL DISTRICT...

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KAKAMEGA CENTRAL DISTRICT CONFIDENTIAL ACCESS TO:- 1M NaOH 1M NH 4 OH 1M HCL 0.01m PB (NO 3 ) 2 Source of heat pH chart (PH=1 to 14) 10ml of solution K Sodium hydrogen carbonate PREPARATION OF SOLUTIONS: 1. Solution J Dissolve 17g of ammonium iron (II) sulphate in 50cm 3 of 2M H 2 SO 4 dilute to 1dm 3 2. Solution K- KMnO 4 Dissolve 1.6g of potassium manganate vii in 20cm 3 of 2 MH 2 SO 4 dilute to 1dm 3 3. Solution R Dissolve 40g of sodium thiosulphate in 1dm 3 of solution 4. Solution S Dissolve 172cm 3 of concentrated hydrochloric acid in 1dm 3 of solution 5. Solid Y is aluminium sulphate 6. Solid Z is oxalic acid. Each candidate will require: Q1. 1. Solution J - 100cm 3 2. Burette 3. Solution K- 100cm 3 4. Pipette 5. 2 conical flasks 6. Filter funnel 7. Retort stand Q2. 1. 120cm 3 of solution R 2. 80cm 3 of solutions 3. 250cm 3 of tap water 4. 25ml or 50ml measuring cylinder 5. 100cm 3 glass beaker 6 5 x 5cm piece of white paper 7. Stop watch or clock. Q3. 1. Solid Y -1spatulaful 2. Solid Z -1spatulaful 3. 6 test tubes 4. 1 red + 1blue litmus papers 5. Metallic spatula 6. pH paper 1. You are provided with :
Solution J:xM ammonium iron(II)sulphate solution Solution K: 0.02M potassium manganate (VII)solution You are required to determine: -The molarity, x of the ammonium iron (II) sulphate - The amount of water of crystallisation, N in ammonium iron (II) sulphate -The formula mass of ammonium iron (II)sulphate. Procedure The ammonium iron (II) sulphate, (NH 4 ) 2 SO 4 FeSO 4 nH 2 O solution provided was made by dissolving 8.5g of the salt in 50.0cm 3 of dilute sulphuric(VI)acid, then making the solution to 250cm 3 using distilled water. Fill the burette with solution K. Pipette 25cm 3 of solution J and release into a conical flask. Titrate J against K until the solution becomes permanent pink. Repeat two more times and complete the table below;- Table 1 I II III Final burrete racing (cm 3 ) Final burrete reading (cm 3 ) Volume of Solution K used (cm 3 ) a) Calculate the average volume of solution K used b) The number of moles of solution K reacting c) Given that equation for the reaction is: MnO 4(aq) + 8H + (aq) + 5Fe 2+ (aq) Mn 2+ (aq) + 5 Fe 2+ (aq) + 4H 2 O (l) Determine: i) The number of moles of iron (II) salt solution J in 25cm 3 of the solution used ii) iii) The molarity of solution J iv) The concentration of solution J in grams per litre d) From your results in C (iii) above, determine: i) the value of “ n ” in the formula (NH 4 ) 2 SO 4 FeSO 4 n H 2 O. (N=14, H= 1, S=32, O=16, Fe=56) 2 -
ii) Correct formula of the iron (II) salt iii) The formula mass of the iron (II) salt 2. You are provided with: i) Sodium thiosulphate containing 40g/dm 3 solution R ii) 2M hydrochloric acid solution S You are to determine the rate of reaction between solution S and the thiosulphate Procedure: Measure 20cm 3 of solution R into an empty 100cm 3 breaker. Place it on a mark ‘ X ’ on a white plain paper. Measure another 20cm 3 of solution S . add into R and start off the stop watch. Then record the time taken for the mark ‘ X ’ to become invisible from above. Repeat the procedure by measuring 17.5cm 3 of solution S and adding 2.5cm 3 of water and complete the table;- Table 2

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