Chemistry Paper 2 Questions and Answers - Form 3 End Term 1 Exams

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  • Answer all the questions in the spaces provided.
  1. The grid below shows part of the table. The letter is not the actual chemical symbols of the elements. Study it and use it to answer the question that follows.
    grid of periodic table Q1 Form 3 End Term 1 2021
    1. Which element is the:
      1. Most reactive non metal. 1mk
      2. Most reactive metal. 1mk
    2. What name is given to element that belongs to the regions marked W.? 1mk
    3. What type of bond if formed in the compound when element Z reacts with element U? Give a reason for your answer. 2mks
    4. Compare the atomic radius of:
      1. T and U. 2mks
      2. Z and X. 2mks
    5. Write the formula of the compound formed when:
      1. Element Z reacts with element Y 1mk
      2. Element P reacts with element V. 1mk
    6. Given that element G has an electron arrangement of 2:8:4 put it in it correct position on the above grid. 1mk
  2. The diagram below shows a set-up that can be used to obtain nitrogen gas in an experiment.
    diagram on set up used to obtain Nitrogen Gas in an experiment
      1. Name liquid L (1mk)
      2. What observation would be made in tube K after heating for some time? (1mk)
      3. Write an equation for the reaction that took place in tube K. (1 mk)
      4. If 320cm3 of ammonia gas reacted completely with the copper?
        1. Volume of nitrogen gas produced. (1mk)
        2. the mass of copper oxide that reacted (3mks)
          (Cu = 63.5, O=16.O, one mole of gas occupies 24 litres at room temperature and pressure)
      5. At the end of experiment the PH of the water in the beaker was found to be about II. Explain (2mks)
    2. In another experiment a gas jar containing ammonia was inverted over a burning splint. What observation would be made? (1mk)
    3. Why is it advisable to obtain nitrogen from air instead ammonia? (1mk)
  3. A form three student from Anestar High School used the set up drawn below in an attempt to prepare dry carbon IV oxide .Study it carefully and use it to answer the questions that follows.
    corrected diagram set up for preparing dry carbon dioxide
    1. Identify two faults in the set up of the apparatus. 2mks
    2. Complete the diagram to show how dry carbon IV oxide gas can be collected. 1mk
    3. Name substances D and E and give their purposes in the above set up
      1. Substance D. 1mk
      2. Purpose 1mk
      3. Substance E. 1mk
      4. Purpose 1mk
    4. Write the equation of the reaction in the flask G. 2mk
    5. State and explain the observation made when dilute sulphuric acid is used in place of hydrochloric acid. 2mks
    6. Give any two uses of carbon IV oxide gas. 2mks
  4. The scheme below shows various reactions starting with hydrogen and nitrogen .study it carefully and answer the question that follows.
    Scheme of various reactions starting with hydrogen and nitrogen
    1. Name the substances:
      1. T 1mk
      2. U 1mk
      3. A 1mk
      4. Q 1mk
      5. W 1mk
      6. C 1mk
    2. Name the catalyst which could be used in:
      1. Step I 1mk
      2. Step II 1mk
    3. Write equations for the reaction occurring in:
      1. Step I 1mk
      2. Step II 2mks (two equations)
    4. What property of ammonia gas is shown in its reaction with copper II oxide? 1mk
    5. Give one industrial use for:
      1. Ammonia 1mk
      2. Nitric acid 1mk
    1. Candle wax is mainly a compound consisting of two elements. Name the two elements. 2mks
    2. The set up below was used to investigate the burning of a candle study it and answer the questions that follow.
      set up used to investigate burning of a candle
      1. What would happen to the burning candle if the pump was turned off? Give a reason 1mk
      2. State and explain the changes in mass that is likely to occur in tube A by the end of the experiment. 3mks
      3. Name two gases that come out through tube C. 2mks
      4. Write two equations for the reactions taking place when a candle burns. 4mks
    1. The flow charts below shows some reaction starting with zinc nitrate. Study it and answer the question that follows.
      flow charts of some reactions starting with zinc Nitrate
      1. State the condition necessary in step I. 1mk
      2. Identify:
        1. Reagent Z 1mk
        2. Gas C 1mk
        3. Acidic product E and F. 2mks
    2. Write equation for the reaction in:
      1. Step I 1mk
      2. Step II 1mk
      3. Step VI 1mk
  7. The diagram below shows the set up used by a student to prepare dry sulphur IV oxide gas. Study it carefully and answer the question that follows.
    set up used by a student to prepare dry Sulphur IV Oxide gas
    1. Complete the diagram to show how to collect dry sulphur (IV) oxide. 1mk
    2. Write an equation for the reaction in the flask. 2mk
    3. Give another pair of chemical that could be used to prepare sulphur (IV) oxide. 2mks
    4. Distinguish between the bleaching action of sulphur IV oxide and chlorine. 2mks
    5. Sulphur IV oxide gas was bubbled through concentrated nitric (V) acid .State and explain the observations made. 2mks

Marking Scheme

      1. T  ✓1
      2. Q  ✓1
    2. Transition elements  ✓1
    3. Ionic/Electrovalent elements ✓1
      There is complete transfer of electrons from Z to U. ✓1
      1. U has more occupied ✓1 energy levels than T, hence has a larger atom radius than T. ✓1
      2. Z has a smaller atomic radius ✓1 than X. Z has more protons and therefore a higher nuclear charge which attracts its electrons more strongly. ✓1
      1. Z3Y2 ✓1
      2. No compound formed as it is stable ✓1
      Correct position of element G in the grid representin periodic table
      1. Liquid L- water ✓1
      2. Black ✓½Copper (II) Oxide changes to brown Copper metal ✓½
      3. 2CuO(s) + 2NH3(g) → 3Cu(s) + 3H2O(l) +N2(g) ✓1
        • 2×24litres of NH3 produce 24litres N2  
          48000cm3 NH3 produce 24000cm3 N2 ✓½
          ∴ 320cm3 NH3 produce   320  × 24000cm3 N2
                                =160cm3 N2  ✓½
        • 2 Moles NH3 produce 3 moles CuO  ✓1
          48000cm3 NH3 produce 238.5g CuO
          ∴ 320cm3 NH3 produce   320  × 238.5g CuO   ✓1
                                          =1.59g  ✓1
      5. Ammonia✓1dissolved in the water to form ammonia solution which is a weak base.✓1
    2. The splint is extingushed as ammonia does not support burning. ✓1
    3. Air has a plentiful supply of nitrogen. ✓1
      • Thistle funnel should not reached the bottom of the flask G  ✓1
      • Delivery tube leading the gas into substance E should dip in it. ✓1
      complete diagram showing how Carbon dryIV Oxide is collected
      1. D-Water✓1 - removes hydrogen chloride gas✓1
      2. E- Conc Sulphuric Acid - Dries the Carbon (IV) Oxide gas
    4. CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) ✓2
    5. The reaction would start but stop immediately ✓1. This is due to formation ✓1 of insoluble Calcium Sulphate which coats the unreacted Carbonate preventing further reaction.
      • Used in fire extinguishers ✓1
      • Used as a refrigerating agent for perishable goods. ✓1
      • Manufacture of sodium Carbonate in the Solvay process.
      • Used in making aerated drinks.
        (Any two correct)
      1. T - Nitrogen ✓1
      2. U - Hydrogen ✓1
      3. A - Ammonium Sulphate ✓1
      4. Q - Nitrogen Gas ✓1
      5. W - Copper ✓1
      6. C - Oxygen gas ✓1
      1. Step I - Iron  ✓1
      2. Step II - Platinum Rhodium ✓1
      1. Step I 
        N2(g) + 3H2(g) double arrows 2NH3(g) ✓1
      2. Step II:
        4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l) ✓1
        4NO2(g) + O2(g) + 2H2O(l) → 4HNO3(aq) ✓1
    4. It is a reducing agent
      1. Ammonia
        • As a fertilizer
        • Manufacture of Nitrogeneous fertilizers
        • As a refrigerant
        • Softening hard water
        • removal of greasy stains
        • Manufacture of Hydrazine that is used as rocket fuel.
          (Any one correct)
      2. Nitric Acid
        • Manufacture of fertilizers
        • Manufacture of explosives
        • Manufacture of dyes and drugs.
        • Purification of metals such as silver and gold
        • etching designs on some metals
          (Any correct one)
    1. Carbon ✓1 and Hydrogen ✓1
        • It would be extingushed ✓1
          This is due to build up of Carbon (IV) Oxide in the funnel around the burning candle ✓1

        • Mass increases ✓1
          Calcium Oxide absorbs water to form Calcium Hydroxide than absorbs Carbon (IV) Oxide gas. ✓1
        • Argon ✓1
        • Nitrogen ✓1
        • C(s) + O2(g) → CO2(g) ✓2
        • 2H2 + O2(g) → 2H2O(l)  ✓2
      1. Heating ✓1
        1. Reagent Z - Na2CO3, K2CO3 or (NH4)2CO3 ✓1
        2. Gas C - Oxygen gas ✓1
        3. Acidic product E and F. 
          E - Nitric (III) acid ✓1
          F- Nitric (V) acid ✓1
      1. Step 1
        2Zn(NO3)2(s) → 2ZnO(s) + 4NO2(aq) +O2(g) ✓1
      2. Step 2
        2NO2(g) + H2O(l) → HNO3(aq) + HNO2(aq) ✓1
      3. Step 6
        Zn(NO3)2(aq) + Na2CO3(aq) → ZnCO3(l) + 2NaNO3(aq) ✓1
              Use Na2CO3, K2CO3 or (NH4)2CO3 in the above equation

    1. complete diagram of how Sulphur IV Oxide is collected
    2. Na2SO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + SO2(g) ✓2
    3. Copper ✓1 and Conc. Sulphuric acid ✓1
    4. SO2 bleaches by reduction ✓½ hence temporary ✓½ Cl2 bleaches by oxidation hence permanent ✓1
    5. Brown fumes of NO2 are produced. SO2 reduces conc. HNO3 forming brown fumes of NO2.

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