Chemistry Paper 3 Questions with No Answers - Maseno Mock Exams 2020/2021

Kenya Certificate of Secondary Education
233/3- CHEMISTRY -Paper 3
(PRACTICAL)
2 ¼Hours

INSTRUCTIONS TO CANDIDATES

1. Answer all the questions in this question paper.
2. You are not allowed to start working with the apparatus for the first 15 minutes of the 2 ¼ hours allowed time for the paper.
3. Use 15 minutes to read through the question paper and make sure that you have all the chemicals and apparatus that you may require.
4. Mathematical table and silent electronic calculators may be used.
5. All workings must clearly be shown where necessary.

QUESTION 1 (17 MARKS)

You are provided with;

1. Solution A containing 2g of sodium hydroxide in 250cm³ of solution
2. Solution B which is sulphuric (vi) acid
3. Solid C

You are required to;

1. Standardize solution B.
2. Determine the mass of solid C that reacts with the standardized solution B.

Procedure I

1. Fill the burette with solution B
2. Transfer 25cm³ of solution B into a 250cm³ volumetric flask. Add distilled water up to the mark. Shake the mixture. Label it solution as D.
3. Drain the burette and rinse it thoroughly
4. Fill the burette with solution A.
5. Pipette 25cm³ of solution D into a conical flask
6. Add 2-3 drops of phenolphthalein indicator.
7. Titrate solution A against D until pink colour just appears.
8. Repeat the above procedure and fill the table 1 below.

Table 1

(3marks)

1. Calculate the ;
   1. Average volume of solution A used (show your working) (1mark)
   2. Molarity of sodium hydroxide solution A (Na =23, O=16, H=1) (1mark)
   3. Number of moles of solution A used for titration. (1mark)
   4. Molarity of the original solution B. (2marks)

Procedure II

1. Rinse the burette thoroughly and fill it with solution B.
2. Transfer 50cm³ of solution into a 100 cm³ beaker.
3. Add all the solid C provided to solution B.
4. Swirl the mixture until there is no more effervescence.
5. Label the mixture as solution E.
6. Rise the burette thoroughly and fill it with solution E.
7. Pipette 25.0cm³ of solution A into a conical flask.
8. Add 2 or 3 drops of phenolphthalein indicator
9. Titrate solution E against solution A until the solution turns just colourless.
10. Repeat the titration and fill the table II below.

Table II

(3marks)

1. Calculate the ;
   1. Average volume of solution E used (show your working) (1mark)
   2. Moles of sulphuric (vi) acid present in 50cm³ of solution B. (1mark)
   3. Number of moles of solution A used for the titration. (1mark)
   4. Moles of sulphuric (vi) acid in solution E used for the titration. (1mark)
   5. Number of moles of sulphuric (vi) acid that reacted with solid C. (1mark)
2. Given that 1 mole of C reacts with 1 mole of Sulphuric (VI) acid and the relative formula mass of C is 106, calculate the mass of solid C used in this experiment. (1mark)

QUESTION 2 (7MKS)

You are provided with 3.0g of potassium nitrate labeled solid G. You are required to determine the enthalpy change of solution of solid G.

Procedure

Using a measuring cylinder, place 30cm³ of distilled water in 100cm³ plastic beaker. Stir the water gently with a thermometer and take the temperature after every half a minute. Record the readings in the table III below. At exactly 2 minutes add all solid G to water at once. Stir well and take the temperature of the mixture after every half a minute up to the 4th minute. Record your results in the table III below.

1.  
   

   Time in Minutes	0	½	1	1½	2	2½	3	3½	4
   Temperature (oC)					X

   (2marks)
2. On the grid provided plot a graph of temperature against time. (2marks)
   
3. On the graph show the change in temperature, ΔT (12mark)
4. Calculate the molar enthalpy of solution (ΔHsoln). Assume density of solution= 1.0g/cm³, specific heat capacity of the solution = 4.2jg-K- , K=39.0, N=14.0, O=16.0) (2¹/₂ marks)

QUESTION 3:- QUALITATIVE ANALYSIS (16MKS)

1. You are provided with solid F.
   You are required to identify the cations and anions in the solid.
   1. Place all the solid F in a boiling tube and add about 10cm3 of distilled water. Shake thoroughly and then filter into a clean test tube. Retain both the filtrate and the residue for the subsequent steps
      

      Observations	Inferences
      1 mark	1 mark

   2. Divide the filtrate into 4 portions.
      1. To the first portion, add aqueous ammonia dropwise till in excess.
         

         Observations	Inferences
         1 mark	1 mark

      2. To the 2nd portion add 3 drops of sodium chloride solution.
         

         Observations	Inferences
         ½ mark	1 mark

      3. To the 3rd portion add about 2 drops of lead (II) nitrate solution and warm the mixture.
         

         Observations	Inferences
         1 mark	½ mark

   3.  
      1. Scrap the residue into a clean test tube, add dilute nitric (v) acid until the solid dissolves. Test for any gas produced using the wooden splint provided.
         

         Observations	Inferences
         1 mark	1 mark

      2. To 2cm³ of the resultant mixture, add 2 drops of potassium iodide
         

         Observations	Inferences
         ½ mark	½ mark

2. You are provided with solid Z. Carry out the tests below and record your observations and inferences in the spaces provided.
   1. Using a metallic spatula, ignite one half of solid Z in a Bunsen flame.
      

      Observations	Inferences
      ½ mark	1 mark

   2. Place the other half of solid Z in a boiling tube. Add about 15cm3 of distilled water and shake well. Use the solution for the following tests.
      1. Place 1cm3 of the solution in a test tube and determine its pH using universal indicator paper.
         

         Observations	Inferences
         ½ mark	½ mark

      2. To about 2cm³ of the solution in a test tube, add 3 drops of acidified potassium manganate (VII).
         

         Observations	Inferences
         1 mark	1 mark

      3. To 2cm³ of the solution in a test tube, add 2 drops of bromine water.
         

         Observations	Inferences
         1 mark	½ mark