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JAMB Chemistry 2008 Question 27

Question 27

Energy Changes

Which of the following reactions is endothermic?

  1. A.C(s) + O2(g) → CO2(g)
  2. B.CaO(s) + H2O(l) → Ca(OH)2(s)
  3. C.C(s) + H2O(g) → CO(g) + H2(g)
  4. D.HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
Show the answer and explanation

Answer: C (C(s) + H2O(g) → CO(g) + H2(g))

Explanation

Making water gas from steam and red-hot coke absorbs heat (the coke cools down). Burning carbon, slaking lime and neutralisation all release heat.