Kenya Certificate Of Secondary Education(KCSE 2013) Chemistry Paper 2

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Kenya Certificate Of Secondary Education(KCSE 2013) Chemistry Paper 2

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1. The grid given below represents part of the periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of the element.
  1. Select a letter which represents an element that loses electrons more readily
    Give a reason for your answer. (2 marks)
  2. Explain why the atomic radius of P is found to be smaller than that of N. (2 marks)
  3. Element M reacts with water at room temperature to produce 0.02 dm³ of gas. Determine the mass of M which was reacted with water. (Molar gas volume at room temperature is 24 dm³, Relative atomic mass of M = 7)
2. Use the information in the table below to answer the questions that follow.
  (These letters are not the symbols of the elements.)
  
  Identify a letter which represents an element in the table calcium, carbon or sulphur. Give a reason in each case.
1. 1. What is meant by the term 'Enthalpy of formation'? (1 mark)
  2. The following enthalpies of combustion of carbon, methane and hydrogen are indicated below:
    
    Enthalpy of combustion of CH₄ = -890 kJ mol^-1
    1. Draw an energy cycle diagram that links the enthalpy of formation of methane to enthalpies of combustion of carbon, hydrogen and methane. (2 marks)
    2. Determine the enthalpy of formation of methane. (2 marks)
2. An experiment was carried out where different volumes of dilute hydrochloric acid and aqueous sodium hydroxide both at 25⁰C were mixed and stirred with a thermometer. The highest temperature reached by each mixture was recorded in the table below:
  1. On the grid provided, plot a graph of hoghest temperature (vertical axis), against volume of hydrochloric acid (horizontal axis). (3 marks)
  2. Using your graph, determine the:
    1. Highest temperature reached; (¹/₂ mark)
    2. Volume of acid and base reacting when the highest temperature is reached; ( ¹/₂ mark)
  3. Calculate the amount of heat liberated during the neutralisation process.
    (Specific heat capacity is 4.2 g^-1K^-1 and the density of the solution is 1.0 g cm^-3) (2 marks)
3. The molar neutralisation between hydrochloric acid and ammonia solution was found to be -52.2 kJ mol^-1, while that of hydrochloric acid and sodium hydroxide was -57. 1 kJ mol^-1. Explain the difference in these values. (2 marks)
1. The diagram below shows the Frasch process used for extraction of sulphur.
  Use it to answer the questions that follow.
  1. Identify X. (1 mark)
  2. Why is it necessary to use super heated water in this process? (1 mark)
  3. State two physical properties of sulphur that makes it possible for it to be extracted by this method. (2 marks)
2. The diagram below shows part of the processes of manufacture of sulphuric (VI) acid. Study it and answer the questions that follow.
  1. Write an equation for the formation of sulphur (IV) oxide from sulphur. (1 mark)
  2. What is the role of concentrated sulphuric (VI) acid in chamber A? (1 mark)
  3. Name two catalysts that can be used in catalystic chamber B. (2 marks)
  4. State two roles of heat exchanger. (2 marks)
3. Explain one way in which sulphur (IV) oxide is a pollutant.
4. What observations would be made when a few drops of concentrated sulphur (VI) acid are added to crystals of sugar? Explain your answer. (1 mark)
1. The set up below can be used to produce sodium hydroxide by electrolysing brine.
  1. Identify the gas Y. (1 mark)
  2. Describe how aqueous sodium hydroxide is formed in the above set-up. (2 marks)
  3. One of the uses of sodium hydroxide is in the manufacturing of soaps.
    State one other use of sodium hydroxide. (1 mark)
2. Study the information given in the table below and answer questions that follow.
  1. Construct an electrochemical cell that will produce the largest emf. (3 marks)
  2. Calculate the emf of the cell constructed in (i) above. (2 marks)
  3. Why is it not advisable to store a solution containing E⁺ ions in acontainer made of H? (2 marks)
1. Describe one method that can be used to distinguish between sodium sulphate and sodium hydrogen sulphate. (2 marks)
2. Describe how a pure sample of lead (II) sulphate can be prepared in the laboratory starting with lead metal. (3 marks)
3. Study the flow chart below and answer the questions that follow.
  1. Write the equation for the reaction in:
    1. Step II (1 mark)
    2. Step IV (1 mark)
  2. State the observations made in step III. Explain. (2 marks)
  3. Name another substance that be used in step V. (1 mark)
1. Distinguish between a neutron and a proton. (1 mark)
2. What is meant by radioactive substance? (1 mark)
3. State two dangers associated with radioactive substances in the environment. (2 marks)
4. The isotopes of hydrogen , deuterium (²₁D) and tritium (³₁T) react to form element Y and neutron particles, according to the equation below:
  ²₁D + ³₁T -----> ^a_bY + ¹₀n
  1. What is the atomic:
    1. mass of Y; (1 mark)
    2. number of Y. (1 mark)
  2. What is tha name given to the type of reaction undergone by the isotopes of hydrogen? (1 mark)
5. 1. What is meant by the half-life of a radioactive substance? (1 mark)
  2. 288g of a radioactive substance decayed to 9g in 40 days. Determine the half-life of the radioactive substance. (2 marks)
1. Give the systematic names for the follwing compounds:
  1. CH₃CH₂COOH; (1 mark)
  2. CH₃CH₂CH₂CHCH₂ (1 mark)
  3. CH C CH₂CH₃. (1 mark)
2. Study the flow chart below and use it to answer the questions that follow:
  1. Identify the organic compound K. (1 mark)
  2. Write the formula of M. (1 mark)
  3. Give one reagent that can be used in:
    1. Step I; (1 mark)
    2. Step II. (1 mark)
  4. Write an equation of the reaction in step III. (1 mark)
3. The structure below represents a type of a cleansing agent.
  
  Describe how the cleansing agent removes grease from a piece of cloth. (3 marks)