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JAMB Chemistry 1982 Question 17

Question 17

Energy Changes

0.16 g of methane when burnt raises the temperature of 100 g of water by 40°C. What is the heat of combustion of methane if the heat capacity of water is 4.2 Jg−1°C−1? (CH4 = 16)

  1. A.1,160 kJ mol−1
  2. B.1,180 kJ mol−1
  3. C.1,560 kJ mol−1
  4. D.1,600 kJ mol−1
  5. E.1,680 kJ mol−1.
Show the answer and explanation

Answer: E (1,680 kJ mol−1.)

Explanation

Heat = 100 × 4.2 × 40 = 16,800 J = 16.8 kJ from 0.16/16 = 0.01 mol, so 16.8/0.01 = 1,680 kJ mol−1.