KAKAMEGA NORTH SUBCOUNTY JOINT EXAMINATIONS KCSE TRIAL 2018

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1 1 Name:... Index No:. Candidate s signature Date KAKAMEGA NORTH SUBCOUNTY JOINT EXAMINATIONS KCSE TRIAL /3 CHEMISTRY PAPER 3 (Practical) JULY ¼ Hours INSTRUCTIONS: Write your name and index Number in the spaces provided. Answer All questions in the spaces provided in the question paper. You are NOT allowed to start working with the apparatus for the first 15 minutes of the 2 ¼ hours allowed for this paper. This time is to enable you to read the question paper and make sure you have all the chemicals and apparatus that you may need. All working MUST be clearly shown where necessary. Mathematical tables and electronic calculators may be used. FORM EXAMINER S USE ONLY Question Max. Score Score Total Score 40 This paper consists of 8 printed Pages Candidates should check the question paper to ensure that all the pages are printed as indicated and no questions are missing

2 1You are provided with: - Aqueous hydrochloric acid, solution A. - Solution B containing 6.3g of dibasic acid H 2 C 2 O 4. 2H 2 O per litre. - Aqueous sodium hydroxide, solution C. - Phenolphthalein indicator. You are required to: - - Standardize the sodium hydroxide solution C - Use the standardized solution C to determine the concentration of A. - React the hydrochloric acid solution A with metal M and determine the mass of 6cm of metal M. PROCEDURE I Fill a burette with solution B. Pipette 25.0cm 3 solution C into a conical flask. Titrate using phenolphthalein indicator. Record your results in table I below. 2 Table I 1 st 2 nd 3 rd Final burette reading cm³ Initial burette reading cm³ Titre (cm 3 ) What is the average volume of solution B used? (4marks) () i) Calculate the concentration of the dibasic acid solution B in moles per litre. (C = 12, H = 1, O = 16) () ii) Calculate the concentration of the sodium hydroxide solution C in moles per litre. ()

3 PROCEDURE II Using a 100cm 3 measuring cylinder, measure 90cm 3 of distilled water and place it into a 250cm 3 beaker and then add 10cm 3 of solution A. Mix the solution well and label it D. Fill a burette with solution D. Pipette 25.0cm 3 of solution C into a conical flask. Titrate using phenolphthalein indicator. Record your results in table II below 3 Table II Final burette reading cm³ Initial burette reading cm³ Titre cm³ 1 st 2 nd 3 rd (4marks) What is the average volume of solution D used? () (i) Calculate the concentration of the diluted hydrochloric acid solution D in Moles per litre. () (ii) Determine the concentration of the original hydrochloric acid solution A in moles per litre ()

4 PROCEDURE III Measure exactly 6cm of metal M provided. Measure 40cm³ of solution A and transfer into a clean boiling tube. Wrap the boiling tube with tissue paper.

4 4 PROCEDURE III Measure exactly 6cm of metal M provided. Measure 40cm³ of solution A and transfer into a clean boiling tube. Wrap the boiling tube with tissue paper. Measure the temperature of this solution and record in table III below. Simultaneously place the metal M into solution A in the boiling tube and start the stopwatch. Record the temperature of the contents in the boiling tube after every 30-second in the table below. Time (sec) Tem ( o C) TABLE III (2marks) i) Draw a graph of temperature against time (3marks)

5 ii) From the graph, determine the highest temperature change. 5 () iii) Calculate the heat of reaction in this experiment. () iv) Given that the molar heat of reaction between metal M and solution A is 1600kJ per mole, determine the number of moles of metal M used. () v) Determine the mass of metal M used in this experiment (M=24). ()

6 2 You are provided with solid H. Carry out the following tests to identify the ions present in H. Record all your observation and inferences in the table below and identify any gas(es) evolved. 6 a) Put a spatula end full of solid H in a dry test-tube and heat gently then strongly for about 2 minutes. Test the gas evolved with moist blue and red litmus papers. b) Place a spatula end-full of solid H in a boiling tube and add 15cm 3 of distilled water and shake well. Divide the solution into four portions. i) To portion one, add sodium hydroxide solution drop wise until in excess. Warm the mixture gently and test the gas evolved with litmus. Observation ii) To portion two, add ammonia solution drop wise until in excess. Observation ½mark iii) To portion three, add five drops of lead (IV) nitrate. Warm the mixture. iv) To portion four, add three drops of Barium chloride solution, followed by 5cm 3 hydrochloric acid solution. ½mark

7 7 3. You are provided with solid Z. Carry out tests below. Record your observations and inferences in the spaces provided. (a) Place solid Z in a test tube add about 10cm 3 of distilled water and shake to dissolve. Divide the resultant solution into 4 portions and use them for tests below (½mk) (½mk) i) To the first portion add dilute sodium hydroxide drop wise until in excess ii) To the second portion add aqueous ammonia drop wise until in excess

8 iii) To the third portion add drops of potassium iodide solution 8 iv) To the fourth portion add a few drops of sodium sulphate solution (½mk) (½mk)

for free kcse past papers visit:

for free kcse past papers visit: Name: Index no..... School:.... Candidate s sign... Date: Class.. 233/3 CHEMISTRY KCSE MOCKS 2017 TIME: 2 ¼ HOURS INSTRUCTIONS TO CANDIDATES: Answer all the questions in the spaces provided in the question