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

INSTRUCTIONS TO CANDIDATES

• 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
   4. Calculate average volume of solution B used. (5mks)
   5. Calculate the number of moles of solution C in 25cm³ of the solution. (2mks)
   6. 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)

Confidential

• 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