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JAMB Chemistry 2021 Question 28

Question 28

Energy Changes

In the preparation of H2SO4(l) as shown in the chemical equation below
SO3(g) + H2O(l) → H2SO4(l)
Given the heats of formation for SO3(g), H2O(l) and H2SO4(l) as −395KJmol−1, −286KJmol−1 and −811KJmol−1 respectively. Calculate the enthalpy (H) change of the reaction.

  1. A.−1032KJ
  2. B.+1032KJ
  3. C.+130KJ
  4. D.−130KJ
Show the answer and explanation

Answer: D (−130KJ)

Explanation

ΔH = ΔHf(products) − ΔHf(reactants) = −811 − (−395 − 286) = −811 + 681 = −130 kJ.