Chemistry Questions and Answers - Form 2 Mid Term 2 Exams 2021

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INSTRUCTIONS TO CANDIDATES

  • Answer ALL questions
  • All workings must be clearly shown where necessary.
  1. Study the word equation below and answer the questions that follow
    Zinc + copper (II) oxide → Zinc Oxide + Copper
    1. Which element has been oxidized?   (1 mark)
    2. Which element has been reduced?   (1 mark)
    3. State the oxidizing agent    (1 mark)
    4. State the reducing agent    (1 mark)
    5. What is oxidation?      (1 mark)
    6. What is reduction?     (1 mark)
  2. State two chemical tests for the presence of water   (2 marks)
  3. The pH of a soil sample was found to be 6.5. An agricultural officer recommended the addition of lime (calcium oxide). State two functions of lime in the soil   (2 marks)
  4. State two advantages of using glass apparatus in the laboratory over plastic apparatus.   1mk
  5. Explain how you would separate a mixture of sand, salt and water    (3 marks)
  6. Solutions F.W and have pH values shown in the table below
     Solution   pH value 
         F     2.0
        W     5.5
        Q     8.0
    1. What do you deduce about the nature of solution W?  (1 mark)
    2. Which solution would react vigorously with sodium hydroxide?    (1 mark)
    3. Which solution is likely to be ammonia solution?  (1 mark)
  7. Students from Kamatu secondary school did an experiment in their laboratory on separation of
    mixtures, Study the set up below and answer he questions that follow.
             F2 Chem Math Q7 2021
    1. Name solid Q   (1 mark)
    2. What is the name given to the above method of separating mixtures?   (1 mark)
    3. What was the use of cold water?   (1 mark)
    4. Why was it possible to separate the two mixtures?   (1 mark)
    5. Identify apparatus Z    (1 mark)
  8. A student reacted hydrochloric acid with sodium carbonate, a salt was formed, water and a colourless
    gas which formed a white precipitate with calcium hydroxide.
    1. Give the name of the salt fomed   (1 mark)
    2. Identify the colourless gas produced  (1 mark)
    3.  Write a word equation for the reaction that took place   (1 mark)
  9. Two samples of water of equal volumes were heated on different flames of a Bunsen bumer as
    shown in the diagram below. The sample in flame I took 8 minutes to boil while that in flame II took 20 minutes to boil.
             F2 Chem Q9 2021
    1. Identify
      1. flame I, give a reason   (2 marks)
      2. Flame II, give a reason   (2 marks)
    2. What other observation was made in this experiment when heating was over? Give a reason
      (2 marks)
  10. In a class experiment a student separately heated equal volumes of distilled water and sea water on identical flames. Identify the water sample which boiled first. Give a reason for your answer  (2 marks)
  11. Use the flow chart below to answer the questions that follow.
             F2 Chem Q11 2021
    1. Identify the following substances     (3 marks)
      1. Substance B
      2. Liquid
      3. Gas D
    2. Name two substances that can be used in chamber A to remove carbon (IV) oxide  (2 marks)
    3. Name a substance that can be used in chamber H to remove substance B   (1 mark)
    4. Identify the following processes   (2 marks)
      1. Process I
      2. Process II
    5. Give one other industrial process in which process II is used,  (1 mark)
    6. Give the physical property of the components of the mixture separated by process II (1 mark)
  12. Study the diagram below and answer the questions that follow:
    F2 Chem Q12 2021
    1. Why is it important to drive out all the air from the combustion tube before lighting the jet?
      (1 mark)
    2. State the observations made in the combustion tube   (2 marks)
    3. What is the purpose of anhydrous copper (II) sulphate in this experiment   (1 mark)
    4. Which property of hydrogen is being investigated in the above experiment   (1 mark)
  13. Students from Bunyore girls high school in Kisumu County went for a symposium in Shimo La Tewa high school in Mombasa county. They realized that, their school buses were bought on the same tem the previous year, the bus for Shimo La Tewa high school had rusted faster than their bus. Give a suitable explanation for this observation.   (3 marks)
  14. When a student was stung by a bee, the teacher applied a solution of aqueous ammonia to the affected area of the skin and the student was relieved off the pain, Explain    (2 marks)
  15. Given the following:
    • leaves from tradescantia
    • Propanone
    • Mortar and pestle
    • Beaker
      Describe how you can make a simple acid-base indicator   (4 marks)
  16. The set up below was used in a chemistry lesson while studying the reaction of metals with water
    F2 Chem Q16 2021
    1. Write a word equation for the reaction taking place in the boiling tube   (1 mark)
    2. State the observations made in this experiment   (1 mark)
    3. Explain the observation you have stated in (b) above   (1 mark)
    4. A solution of phenolphthalein indicator was added to the resulting solution. State and explain what was observed.  (2 marks)
    5. Predict the pH value of the resulting solution. Explain   (2 marks)
  17. The diagrams below represent two methods of gas collection in the laboratory
             F2 Chem Q17 MT2 2021
    1. Give their names     (2 marks)
      A
      B
    2. State the property of gases collected by the above methods
      A-
      B-(2 marks)
  18. In an experiment to investigate the percentage of oxygen in air, 200 cm3 of air was passed over the heated copper turning repeatedly until a constant volume of air remained. 160 cm3 of air remained at the end of the experiment.
    1. Determine the percentage volume of air used up during the experiment   (3 marks)
    2. Name two gases that remained in 160 cm3 of air    (2 marks)
  19. List down 3 mineral acids that are commomn;y used in the laboratory.  (3 marks)
  20. Study the diagram below and answer the questions that follow.
            F2 Chem Q20 MT2 2021
    1. What is the name given to the above method of preventing rusting?  (1 mark)
    2. When the set up is exposed to atmosphere the iron exposed in the crack does not rust. Explain 
      (1 mark)


MARKING SCHEME 

  1.  
    1. Zinc
    2. Copper (II) oxide
    3. Copper (II) oxide
    4. Zinc
    5. Addition of oxygen to a substance
    6. Removal of oxygen from a substance
  2.  
    • It turns white anhydrous copper (II) sulphate to blue
    • It turns blue cobalt chloride paper pink
  3.  
    • To add calcium as a mineral in the soil
    • To neutralize the acidity in the soil (6.5)
  4.  
    • Glass can be heated while plastic cannot
    • Glass apparatus allows one to make observation when doing an experiment ie they are visible   from the side
  5.  
    • Mix sand and salt with water
    • Filter the sand using a sieve and get sand as a residue
    • Evaporate the filtrate to dryness to obtain crystals of salt
  6.  
    1. It is a weak acid
    2. F
    3. Q
  7.  
    1. Iodine
    2. Sublimation
    3. To condense the hot iodine vapour
    4. Because iodine can sublime while sodium chloride cannot
    5. Tripod stand
  8.  
    1. Sodium chloride
    2. Carbon (IV) oxide
    3. Sodium carbonate + hydrochloric acid → sodium chloride + carbon (iv) oxide + water
  9.  
    1.  
      1. Flame I.
        Non-luminous flame, used less time to boil:
      2. Flame II, 
        Luminous flame; used more time to boil;
    2. The beaker in flame II was black at the bottom; because of soot produced by the flame when the air hole is closed carbon burns in limited supply of oxygen
  10. Distilled water boiled first; this because sea water has dissolved salts that act as impurities hence raising the boiling point:
  11.  
    1.  
      1. Water vapour
      2. Liquid air
      3. Oxygen
    2.  
      • Concentrated sodium hydroxide
      • Concentrated potassium hydroxide
    3. Silica gel
    4.  
      1. Purification
      2. Fractional distillation
    5. Separation of the contents of crude oil
    6. They have different but close boiling points
  12.  
    1. Burning hydrogen in presence of oxygen in air is explosive
    2.  
      • The black copper (II)oxide changed to brown
      • The white anhydrous copper (II) sulphate turned blue
    3. To absorb the water vapour produced in the combustion tube;
    4. Reducing property;
  13. In Mombasa county the environment is salty compared to Kisumu county: the salty environment speeds up the rate of rusting: in Kisumu the rusting process is not speeded by salty environment hence it is slow;
  14. The bee sting injects acid to the affected part: ammonia is a base which neutralize the acidity which relieves off the pain:
  15.  
    1. Cut the tradescantia leaves and place them in a mortar:
    2. Using a pestle crush the leaves to produce the juice:
    3. Add propanone as you continue crushing:
    4. Decant the extract in a beaker:
  16.  
    1. Calcium + water → calcium hydroxide + hydrogen gas
    2. The burning splint burns with a pop sound
    3. Hydrogen gas is produced which bums with a pop sound in air
    4. The solution turned pink; solution formed ie calcium hydroxide is an alkaline:
    5. 11, 12, 13, 14; the solution is an alkaline;
  17.  
    1. A- Upward delivery/downward displacement of air:
      B-Downward delivery/ upward displacement of air;
    2. A- They are less dense than air/ they are lighter than air,
      B - They are denser than air,
  18.  
    1. Initial volume of air = 200 cm3
      Final volume of air - 160 cm3
      Volume of air used= 40 cm3;
      Percentage volume of air = volume of air used x 100:
                                                   Initial volume
                                           = 40 x 100 =20%
                                                   200
                                           = 20%:
    2.  
      • Carbon (IV) oxide;
      • Nitrogen;
  19.  
    1. Hydrochloric acid;
    2. Nitric acid:
    3. Sulphuric acid
  20.  
    1. Galvanization
    2. Zinc is more reactive than iron and hence reacts with oxygen;

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