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JAMB Chemistry 1985 Question 30

Question 30

Energy Changes

The energy change (ΔH) for the reaction CO(g) + ½O2(g) → CO2(g) is (ΔHf(CO) = −110.4 kJ mol−1) (ΔHf(CO2) = −393 kJ mol−1)

  1. A.−503.7 kJ
  2. B.+503.7 kJ
  3. C.−282.9 kJ
  4. D.+282.9 kJ
  5. E.+393.3 kJ
Show the answer and explanation

Answer: C (−282.9 kJ)

Explanation

ΔH = (heats of formation of products) − (heats of formation of reactants) = −393 − (−110.4 + 0) ≈ −283 kJ, so the answer is −282.9 kJ.