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JAMB Chemistry 2014 Question 27

Question 27

Energy Changes

If the change in free energy of a system is −899 J mol-1 and the entropy change is 10 J mol-1 K-1 at 25 °C, calculate the enthalpy change.

  1. A.+2081 J mol-1
  2. B.−2081 J mol-1
  3. C.−649 J mol-1
  4. D.+649 J mol-1
Show the answer and explanation

Answer: A (+2081 J mol-1)

Explanation

ΔG = ΔH − TΔS, so ΔH = ΔG + TΔS = −899 + 298 × 10 = +2081 J mol-1.