KCSE 2014 Chemistry Paper 2 Questions with Marking Scheme

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    1. The set up below was used to prepare dry hydrogen chloride gas, and investigate its effect on heated iron fillings.
      sulphuric acid iron fillings


      1. Name substance L. (1 mark)
      2. Name liquid M. (1 mark)
      3. What will be observed in tube B? (1 mark)
      4. Write an equation for the reaction that occurs in tube B. (1 mark)
      5. Why is the gas from tube B burnt? (1 mark)

      1. Explain the following observations:
        1. A white precipitate formed when hydrogen chloride gas is passed through aqueous silver nitrate. (1 mark)
        2. Hydrogen chloride gas fumes in ammonia gas. (1 mark)
      2. State two uses of hydrogen chloride gas. (1 mark)

    2. The diagram below is a representation of an industrial process for the manufacture of a bleaching powder.


      chlorine bleaching


      1. Name substance Q. (1 mark)
      2. When the bleaching powder is added to water during washing, a lot of soap is used. Explain. (1 mark)


  1.  
    1. The grid below represents part of the periodic table. Study it and answer the questions that follow. The letters are not the actual symbols of the elements.

      Periodic table

      1. Select the most reactive metal. Explain. (2 marks)
      2. Select the element that can form an ion with a charge of 3-. (1 mark)
      3. Select an alkaline earth metal. (1 mark)
      4. Which group I element has the highest first ionization energy? Explain. (2 marks)
      5. Element A combines with chlorine to form a chloride of A. State the most likely pH value of a solution of the chloride of A. Explain. (2 marks)

      1. Explain why molten calcium chloride and magnesium chloride conduct electricity while carbon tetrachloride and silicon tetrachloride do not. (2 marks)
      2. Under the same conditions, gaseous neon was found to diffuse faster than gaseous fluorine. Explain the observation. (F= 19.0: Ne= 20.0) (2 marks)


    1. Draw the structures of the following:
      1. Butan-1-ol (1 mark)
      2. Hexanoic acid. (1 mark)

    2. Study the flow chart below and answer the questions that follow.
      organic chemistry
      1. State the conditions necessary for fermentation of glucose to take place. (1 mark)
      2. State one reagent that can be used to carry out process S. (1 mark)
      3. Identify gases: (2 marks)
        P…………
        T…………
      4. How is sodium hydroxide kept dry during the reaction? (1 mark)
      5. Give one commercial use of process R. (1 mark)

    3. When one mole of ethanol is completely burnt in air, 1370 KJ of heat energy is released. Given that 1 litre of ethanol is 780 g, calculate the amount of heat energy released when 1 litre of ethanol is completely burnt. (3 marks)
      (C = 12.0; H = 1.0; O = 16.0)

    4. State two uses of ethanol other than an alcoholic drink. (2 marks)


    1.  Other than temperature, state two factors that determine the rate of chemical reaction. (1 mark)

    2. A solution of hydrogen peroxide was allowed to decompose and the oxygen given off collected. After 5 minutes, substance G was added to the solution of hydrogen peroxide. The total volume of oxygen evolved was plotted against time as shown in the graph below

      Hydrogen Peroxide Decomposed


      1. Describe the procedure of determining the rate of reaction at minute 12. (3 marks)
      2. How does the production of oxygen in region AB compare to that in region BC? (2 marks)
      3. Write an equation to show the decomposition of hydrogen chloride. (1 mark)

    3. Sulphur (IV) oxide reacts with oxygen to form Sulphur (VI) oxide as shown in the equation below:
      sulphur (iv) oxide

      1. Explain the effect of the yield SO3 of lowering the temperature for this reaction. (2 marks)
      2. Name one catalyst used for the reaction. (1 mark)


    1. The scheme below shows some of the reactions of solution D. Study it and answer the questions that follow.

      Reactions


      1. Give a possible cation present in solution D. (1 mark)
      2. Write an ionic equation for the reaction in step II. (1 mark)
      3. What observations would be made in step V? Give a reason. (2 marks)
      4. Explain why the total volume of hydrogen gas produced in step I was found to be very low although calcium and solution D were in excess. (2 marks)
      5. State one use of substance E. (1 mark)

    2.  Starting with sodium chloride, describe how a pure sample of lead (II) chloride can be prepared in the laboratory. (3 marks)

      1. State a property of anhydrous calcium chloride which makes it suitable for use as a drying agent for chlorine gas. (1 mark)
      2. Name another substance that can be used to dry chlorine gas. (1 mark)


  2. The diagram below represents a set up of an electrolytic cell that can be used in the production of aluminium.

    electrolytic cell


    1. On the diagram, label the anode. (1 mark)

    2. Write an equation for the reaction at the anode. (1 mark)

    3. Give a reason why the electrolytic process is not carried out below 9500C. (1 mark)

    4. Give a reason why the production of aluminium is not carried out using reduction process? (1 mark)

    5. Give two reasons why the aluminium ions are discharged. (2 marks)

    6. State two properties of duralumin that make it suitable for aircraft industry. (2 marks)

    7. Name two environmental effects caused by extraction of aluminium. (2 marks)

  3.  
    1. Dissolving of potassium nitrate in water is an endothermic process. Explain the effect of increase in temperature on the solubility of potassium nitrate. (2 marks)

    2. The table below shows the solubilities of potassium sulphate and potassium chlorate (V) at different temperatures. pottasium chlorate

      1. Draw the solubility curves for both salts on the same axis. (Temperature on the X- axis) (3 marks)

        mathkcse2013q23

      2. A solution of potassium sulphate contains 20g of the salt dissolved in 100g of water at 1000C. This solution is allowed to cool to 250C.
        1. At what time will the crystals first appear? (1 mark)
        2. What mass of crystals will be present at 250C? (1 mark)
      3. Which of the two salts is more soluble at 300C? (1 mark)
      4. Determine the concentration of potassium nitrate in moles per litre when the solubility of the two salts is the same. (K = 39.0; O = 16.0; S =32.0)
      5. 100g of water at 1000C contains 19g of potassium chlorate (V). Describe how a solid sample of potassium sulphate at 600C can be obtained. (2 marks)

MARKING SCHEME

  1.                                
    1.                            
      1. Sodium chloride / potassium chloride /rock salt. (1 mark)
      2. Concentrated sulphuric (VI) acid (1 mark)
      3. Grey solid turns green (1 mark)
      4. Fe(s) + 2 HCl(g) → FeCl2(s) + H2(g). (1 mark) 
      5. To avoid explosion. (1 mark)
    2.                                      
      1.                          
        1. The gas reacts with silver nitrate to form insoluble silver chloride. (1 mark)
        2. Both gases form ammonium chloride which is white. (1 mark)
      2.                        
        • To make hydrochloric acid.
        • Manufacture of ammonium chloride.
        • Manufacture of PVC.
        • Making chloroethene /vynil chloride (1 mark)
    3.            
      1. Q is Ca(OH)2 (aq) /calcium chloride (1 mark)
      2. Presence of Ca2+ which make water hard / forms scum. (1 mark)
  2.                                    
    1.                    
      1. K - Has largest atomic radius / it most readily loses its outermost electron.
      2. B /N (1 mark)
      3. D / Mg (1 mark)
      4. A (1) It has the smallest/smaller atomic radius/ its outermost electron is more/most strongly held by nucleus.(1) (2 marks)
      5. PH is seven (7). The chlorides of group 1 elements are neutral salts. (2 marks)
    2.                    
      1. Both CaCl2 and MgCl2 have mobile ions in molten state (1) while both CCl4 and SiCl4 are molecular compounds with no mobile ions (1).
      2. Neon has molar mass of 20 while Flourine has a molar mass of 38 (1). Therefore Neon diffuses faster. (1) Since it has a lower molecular mass the faster the rate of diffusion.
  3.                              
    1.                                        
      3a jhgatyfdyatfd(1 mark)
    2.                    
      1. Yeast/enzymes/zymase/temperature of 35 - 40ºC. (2 marks)
      2. Acidified KMnO4 or K2Cr2O7 (1 mark) 
      3. P = Ethene / C2H4 (1 mark)
        T = Methane / CH4 (1 mark)
      4. Addition of CaO or NaOH (1 mark)
      5. Converting oils into fats. (1 mark)
        Manufacture of mangarine /hardening oils.
    3. CH3 CH2 OH →1370 kJ(1)
      R.M.M. of CH3CH2OH           46(1/2)
      1 litre (780g) = 1370 × 780 (1)
                                     46
      = 23,230.43 kj (1/2)
    4. Fuel
      Solvent
      Anti-septic
      Manufacture of synthetic fibres
      Manufacture of gasohol
      Manufacture of ethanoic acid/vinegar
      Used in themometers
      Manufacture of other organic compounds.
      Any 2 (2 marks)
  4.                                
    1.                        
      • Pressure
      • Concentration
      • Catalyst
      • Particle size/surface area
      • Light intensity (1 mark)
    2.                  
      1. Draw a tangent to the graph at 12 min. (1)
        Determine change in volume(1/2) /Calculate gradient.
        Determine change in time.(1/2)
        Divide change in volume by change in time (1)
      2. AB Low production of gas(1) while BC the rate is very high because catalyst B was added. (1)
      3. 2H2O2(aq) O2(g)+ 2H2O(l)(1)
    3.                    
      1. Lowering the temperature shifts the equilibrium to the right /favours the forward reaction. (1) Hence more SO3 will be produced. (1)
      2. Platinum or Vanadium pentoxide/vanadium (v) oxide / V2O5/ platinised asbestos any (1 mark)
  5.                                
    1.                
      1. Cation present in solution D is H+ (1 mark) 
      2.  Ba2+(aq) + SO42-(aq) → BaSo4(s)
      3. Zinc disappears /zinc dissolves.
        Blue colour disappears and brown solid is deposited.(1)
        Zinc being more reactive than copper displaces /Cu2+ ions from solution, copper which is brown is formed.(1)
        Apparatus feels warm/reaction is exothermic.
      4. The reaction forms CaSO4 which is insoluble(1) the insoluble CaSO4 coats the surface of calcium preventing further reaction. (1)
      5. Making plaster of paris / making plaster. (1)
    2. Dissolve sodium chloride in distilled water. (1/2) Add aqueous lead nitrate. (1)
      Filter the mixture, (1/2) wash residue with distilled water. (1/2)
      Dry residue in oven at controlled temperatures/ between filter papers.( 21 )
    3.                    
      1. It absorbs moisture/water. / deliquescent / hygroscopic (1)
      2. Conc. H2SO4(1) / H2SO4(l) / concentrated sulphuric (VI) acid/
  6.                            
    6 jkagtyfda
    1.  On the diagram (1)
    2. 2O2-(l) → O2(g) + 4e (1)
    3. Below 950 ºC, the electrolyte is not in molten state.(1)
    4. Aluminium is more reactive than carbon (coke)(1) therefore the reduction process is not possible / carbon / carbon (II) oxide / coke cannot reduce Al2O3.
    5.                  
      • Aluminium is less reactive than Sodium (1)  therefore: It is preferentially discharged.
      • Al3+ ions are in higher concentration than Na+.(1)
    6.                  
      • Global warming due to production of CO2 / F2 pollution. (1)
      • Creation of gullies during excavation. (1)
    7.                
      • Light (1)
      • Strong (1)
        6b jagvjtdfatyd
  7.                    
    1. Solvent molecules move further apart hence more solid particles dissolve / creating more space for solid particles(1)
      therefore:The solubility increases.(1)
    2.                                                        
      1. (3 marks)   
      2.                        
        1. Value read from the graph (1)
        2. 10.5 g (value read) (1)
      3. Salt identified from the graph (1)
      4. Solubility of K2SO4 = 12.8 (1/2) g/100 g
        Mass of K2SO4 in 100 cm3 =12.8 × 1000 (1/2)
                                                       100
        = 128 g(1/2)
        Molar mass of K2SO4 = 174g (1/2) 
        Conc of K2SO4 = 128 (1/2) = 0.7356M (1/2)
                                 174
      5. Filter crystals of K2SO4(1/2)
        Dry between filter papers. (1/2)

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