CHEMISTRY PAPER 3 - 2017 KITUI MOCK EXAMINATION

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  1. You are provided with;
    • Aqueous hydrochloric acid labeled solution A.
    • Solution B containing 8.0 g per litre of sodium carbonate.
    • An aqueous solution of substance C labeled solution C

    You are required to determine the;

    • Concentration of solution A.
    • Enthalpy of reaction between hydrochloric acid and substance C

    Procedure I
    Using a pipette and pipette filler, place 25.0cm3 of solution A into a 250ml, volumetric flask.
    Add distilled water to make 250cm3 of solution. Label this solution D.
    Place solution D in a burette. Clean the pipette and use it to place 25.0cm3 of solution B into a conical flask. Add 2 drops of methyl orange indicator provided and titrate with solution D. Record your results in table 1. Repeat the titration two more times and complete the table. (4 marks)

       I  II  III
     Final burette reading       
     Initial burette reading      
     Volume of solution D used (cm3)      
    Calculate;
    1. Average volume of solution D used.   (1 mark)
    2. Concentration of sodium carbonate in solution B.
      (Na = 23.0, O = 16.0, C = 12.0)      (1 mark)
    3. Concentration of hydrochloric acid in solution D.  (2 marks)
    4. Concentration of hydrochloric acid in solution A.  (1 mark)
    Procedure II
    Using a clean burette, place 2 cm3 of solution A into a boiling tube. Take the initial temperature of the solution in the boiling tube and record it in table 2. Using a clean measuring cylinder, measure 14 cm3 of solution C into 100cm3 beaker and add it to a solution A in the boiling tube. Stir the mixture immediately with a thermometer and record in table 2 the highest temperature reached. Repeat the experiment with the other sets of volumes of A and C in the table and complete it.
    (Rinse the thermometer and the boiling tube with distilled water after each experiment) (5 marks)
    Volume of solution A (cm3  2  4  6  8  10  12  14
     Volume of solution C (cm3)  14  12  10  8  6  4  2
     Initial temperature of solution C (0C)              
     Highest temperature of solution C (0C)              
     Change in temperature ΔT(0C)              
    1. On the grid provided, draw a graph of ΔT (vertical axis) against volume of solution A used. (3 marks)
    2. From the graph, determine;
      1. The maximum change in temperature.   (½ mark)
      2. The volume of solution A required to completely neutralize solution C.   (½ mark)
    3. Calculate the;
      1. Number of moles of hydrochloric acid required to completely neutralize solution C.  (1 mark)
      2. Molar enthalpy of reaction between hydrochloric acid and substance C (in kilojoules per mole of hydrochloric acid). Assume the specific heat capacity of the solution is 4.2 Jg-1K-1 and density of solution is 1.0 gcm-3.  (2 marks
  1. You are provided with solid Q. Carry out the following tests on Q and record your observations and inferences in the spaces provided.
    1. Place a spatula of solid Q into a boiling tube and add 12 cm3 of distilled water.
      Shake the mixture thoroughly. Divide the mixture into five portions.
       Observations  Inferences

      1 mark

      1 mark

    2. To the first portion, add 5 cm3 of 2M Nitric (V) acid.
       Observations  Inferences

      1 mark

      1 mark

    3. To the second portion, add four drops of lead (II) nitrate solution.
       Observations  Inferences

      1 mark

      1 mark

    4.  To the third portion, add four drops of Barium nitrate solution.
       Observations  Inferences

      1 mark

      1 mark

    5.  To the fourth portion, add sodium hydroxide solution dropwise until in excess.
       Observations  Inferences

      1 mark

      1 mark

    6. To the fifth portion, add ammonia solution dropwise until in excess.
       Observations  Inferences

      1 mark

      1 mark

  2. You are provided with substance Y.
    Carry out the following tests on Y and record your observations and inferences in the spaces provided.
    1. Describe the appearance of solid Y.   (1 mark)
    2. Scoop a little solid Y with a clean metallic spatula and ignite it using non-luminous part of the Bunsen burner flame.
       Observations  Inferences

      1 mark

      1 mark

    3. Add about 10 cm3 of distilled water to the remaining solid Y in a boiling tube.
      Divide the resulting mixture into 2 portions.
      1. To the portion one, add 3 drops of acidified potassium manganate (VII) solution.
         Observations  Inferences

        1 mark

        1 mark

      2. To portion two, add sodium hydrogen carbonate.
         Observations  Inferences

        1 mark

        1 mark


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