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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 40oC. 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 50oC, 60oC, 70oC and 80oC 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 65oC. (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)
         
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