Chemistry Paper 3 Form 3 Questions and Answers - End Term 2 Exams 2021

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Chemistry Paper 3 Form 3 End Term 2 Exams 2021 with Marking Schemes


  • Answer all questions on the space provided
  • All working Must be clearly shown
  1. You are provided with;
    • Solution A 0.2MNaOH
    • Solution B Hydrochloric acid
    • Solution C sodium Carbonate solution

    You are required to standardize hydrochloric acid using solution A and hence determine the morality in moles per liter of solution C sodium carbonate

    Procedure I
    Using a pipette transfer 25cm3 solution A into conical flask add 2 to 3 drops phenolphthalein indicator then titrate with hydrochloric acid provided in a beaker from burette. Shake the conical flask after each additional and note the volume required to neutralize sodium hydroxide solution. Record your results in the table below.
    1. What is the average volume of solution B? (5mks)
    2. Calculate the number of moles of solution B required to complete neutralize solution A. (3mks)
    3. Calculate the molarity in moles per liter of solution B hydrochloric acid. (1mk)

    Procedure II

    Rinse the pipette thoroughly then pipette 25cm3 of solution C sodium carbonate into clean conical flask then add 2 to 3 drops of phenolphthalein indicator. Refill the burette with solution B and use it to titrate content of the conical flask. Shake the flask after each addition of the acid solution B and note the volume of the acid required to neutralize 25cm3 of sodium carbonate solution C. 
    Record your results in table below
    1. Calculate average volume of solution B used. (5mks)
    2. Calculate the number of moles of solution C in 25cm3 of the solution. (2mks)
    3. Calculate the molarity of solution C in Mole per liter. (1mk)
  2. You are provided with solid D. Carry out tests below and record your observation and inferences in the table below.
    1. Describe the appearance of sold D. (2mks)
    2. Take a boiling tube, add all solid D and add about 10cm3 of distilled water. Shake the mixture
       Observations  Inference
       (1mk)  (1mk)
    3. Divide the solution obtained above into five portions. To the first portion add drops of lead (ii) Nitrate solution. 
       Observations  Inference
       (1mk)  (2mks)
    4. To the second portion add 3 drops of barium Nitrate.
       Observations  Inference
       (1mk)  (1mk)
    5. To the third portion add few then excess drops of ammonia solution.
       Observations  Inference
       (1mk)  (2mk)
    6. To the fifth portion, add drops of hydrochloric acid then boil the mixture.
       Observations  Inference
       (2mk)  (1mk)
    7. Give the formula of the anion acid cation present in substance D. 
      Cation…………………………………… (1mk)
      Anion ……………………………………. (1mk)


  • Solution A – 0.2M NaOH
    - 80cm3 per students
  • Solution B – 0.2MHCl
    - 150cm3 per student
  • Solution C – 0.05M Na2CO3
    - 80 cm3 per student
  • Solid D (0.5g Pb(NO3)2)
  • Burette
  • Pipette
  • Complete stand
  • 3 conical flask
  • Access – Phenolphthalein indicator and a dropper
    -0.1M pb(NO3)2 and a dropper
    -2M NH4OH 
    -0.5M Ba(NO3)2 and a dropper
    -0.5M HCl  and a dropper
  • 6 test tubes in rack
  • 1 boiling tube
  • Wash bottle with distilled water

Marking Scheme

    1. CT✓
      Average = 25.1cm3
    2. Moles of NaOH = 25.0 x 0. 2
      = 0.005moles✓
      Moles of acid, moles ratio 1:1✓
      = 0.005 x 1
      = 0.005moles✓
    3. 0.005 x 1000 ✓½
      = 0.2M ✓½
    4. Volume average = 12.5cm3
        ± 0.2✓½
    5. Moles of the acid = 12.5 x 0.2
      = 0.0025moles✓
      Moles of carbonate, moles ratio 1:2✓½
      = 0.0025/= 0.00125 moles ✓½
    6. = 0.00125 x 1000
    1. White/ colorless✓
      Crystalline solid✓

       Observations  Inference
       Solid dissolved forming a colorless solution ✓ (1mk) Soluble salt ✓
      Absence of colored ions (1mk)
       Observations  Inference
       No white precipitate 
       Observations  Inference
       No white precipitate 
       Observations  Inference
       White precipitate
       Insoluble in excess
    6.  Observations  Inference

       No effervescence
       White precipiatate that dissolve on boiling

       Pb2+ present
      Cation Pb2+ (1mk)
      Anion NO3-  (1mk)

      The only soluble salts of lead is Lead (II)Nitrate  
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