Chemistry Paper 3 - Alliance High School Pre-Trial Examination 2018

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CHEMISTRY
PAPER 3
PRACTICAL
TIME: 2¹/₄ HOURS

ALLIANCE HIGH SCHOOL
PRE-TRIALS MAY 2018

INSTRUCTIONS:

• Answer ALL questions in the spaces provided.
• You are NOT allowed to start working with the apparatus for the first 15 minutes. This time will enable you to read through the question paper and make sure you have all the chemicals and apparatus required.
• Mathematical tables and electronic calculators may be used.
• All working must be clearly shown where necessary.

1. You are provided with:
   -Solution P of potassium manganate (VII)
   -0.05M solution Q of oxalic acid
   -Solution R containing 4.9g of ammonium iron (II) sulphate (NH₄)₂SO₄FeSO₄6H₂O, in 250cm³ of water
   
   You are required to:
   1. Determine the rate of reaction between oxalic acid and Potassium manganate (VII).
   2. Standardize the solution P.
   
   
   PROCEDURE I:
   Using a 10 ml measuring cylinder, place 1 cm³ of solution P into each of the five(5) test-tubes in a rack. Using a 50ml measuring cylinder place 19 cm³ of solution Q into a boiling tube. Prepare a water bath by placing about 200cm³ of water into a beaker and start to heat. Place a thermometer into solution Q and place it in the warm water until it attains a temperature of 40^oC. Remove the boiling tube from the water - bath and place it in the test tube rack. Add the first portion of solution P immediately and at the same time, start a stop watch. Record the time taken for solution P to be decolourised in table 1 below. Repeat the procedure at temperatures of 50^oC, 60^oC, 70^oC and 80^oC to complete the table.
   
   

   Temperature of solution Q (oC)	40	50	60	70	80
   Time taken for decolourisation (t secs)
   1/t sec -1

     (6 mks)
   
   1. Plot a graph of ¹/_t against temperature. (X axis) (3 mks)
   2. From the graph, determine the time taken for the mixture to decolourise at 65^oC. (2 marks)
   3. How does the rate of reaction between oxalic acid and potassium manganate (VII) vary with temperature? (1 mark)
   
   
   PROCEDURE II
   Fill a burette with solution P. Pipette 24cm³ of solution R into a conical flast and titrate the solution P against solution R until a permanent pink colour just appears. Record your results in table II below and repeat the procedure to fill the table.
   
   

   Titre	I	II	III
   Final burette reading (cm3)
   Intial burette reading (cm3)
   Volume of solution P used (cm3)

    (4 mks)
   1. Determine the average volume of P used. (1 mk)
   2. Calculate the concentration of solution R in moles per litre. (Fe=56,S=32,O=16,N=14,H=1) (2 mks)
   3. Find the number of moles of solution R used. (1 mk)
   4. Given the ionic equation for the reaction is
      5Fe²⁺(aq) + MnO₄^-(aq) + 8H⁺(aq) ------> 5Fe³⁺(aq) + Mn²⁺(aq) + 4H₂O(l);
      Find the number of moles of solution P used. (1 mk)
   5. Determine the concentration of the Potassium Manganate (VII), solution P in moles per litre. (2 mks)
2. You are provided with solid B. Carry out the tests below and record your observations and inferences in the table below.
   1. Place half a spatula full of solid B in a clean dry test-tube and heat gently then strongly.
      

      Observations	Inferences
      (1 mk)	1(mk)

       
   2. Place the remaining solid B in a boiling tube and add about 5cm³ of distilled water and shake well. Divide the resulting mixture into four portions for the tests below.
      

      Observations	Inferences
      (1 mk)	1(mk)

       
      1. To the first portion add Sodium hydroxide solution dropwise until in excess.
         

         Observations	Inferences
         (1 mk)	1(mk)

          
      2. To the second portion add 2-3 drops of dilute Sulphuric (VI) acid.
         

         Observations	Inferences
         (1 mk)	1(mk)

          
      3. To the third portion add aqueous ammonia dropwise until in excess.
         

         Observations	Inferences
         (1 mk)	1(mk)

          
      4. To the fourth portion add 2-3 drops of barium nitrate solution.
         

         Observations	Inferences
         (1 mk)	1(mk)

          
3. You are provided with solid L. Carry out the tests below on L and record the observations and inferences in the spaces provided.
   1. Place half of solid L in a boiling tube and add about 5cm³ of distilled water. Divide the resulting mixture into two portions for the tests below:
      1. To the first portion, add 2-3 drops of acidified Potassium manganate (VII).
         

         Observations	Inferences
         (1 mk)	1(mk)

          
      2. To the second portion, dip a piece of blue litmus paper.
         

         Observations	Inferences
         (1/2 mk)	(1/2 mk)

          
      3. Place the remaining solid L in a metallic spatula and ignite it.
         

         Observations	Inferences
         (1 mk)	1(mk)