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Friday, 14 August 2026
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Chemistry Past Questions and Answers

Topic: Energy changes

Jamb Chemistry Questions - Energy changes

Question 1:
The part of the total energy of a system that accounts for the useful work done in a system is known as
  • A Enthalpy change
  • B None of the above
  • C Gibb's free energy
  • D Entropy
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Question 2:
When copper (ii) sulphate solution is treated with excess ammonium hydroxide, a precipitate is first formed, and then this dissolves to give a deep blue solution. This deep blue solution is a
  • A Cu(OH)<sub style='font-size: smaller;'>2</sub>
  • B CuSo<sub style='font-size: smaller;'>4</sub>.5H<sub style='font-size: smaller;'>2</sub>O
  • C (NH<sub style='font-size: smaller;'>4</sub>)<sub style='font-size: smaller;'>2</sub>SO<sub style='font-size: smaller;'>4</sub>
  • D Cu(NH<sub style='font-size: smaller;'>3</sub>)<sub style='font-size: smaller;'>4</sub>(OH)<sub style='font-size: smaller;'>2</sub>
  • E CuSO<sub style='font-size: smaller;'>4</sub>.(NH<sub style='font-size: smaller;'>4</sub>)<sub style='font-size: smaller;'>2</sub>SO<sub style='font-size: smaller;'>4</sub>.2H<sub style='font-size: smaller;'>2</sub>O
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Question 3:
The number of grammes of potassium hydroxide in 250cm3 of one molar solution is?
(K = 39, O = 16, H = 1)
  • A 40g
  • B 52g
  • C 100g
  • D 26g
  • E 14g
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Question 4:
In which of the following is the entropy change positive?
  • A H<sub style='font-size: smaller;'>2</sub>O<sub style='font-size: smaller;'>(I)</sub> → H<sub style='font-size: smaller;'>2</sub>O<sub style='font-size: smaller;'>(g)</sub>
  • B Cu<sup style='font-size: smaller;'>2+</sup><sub style='font-size: smaller;'>(aq) + Fe(s)</sub> → Fe<sup style='font-size: smaller;'>(2+)</sup> + Cu<sub style='font-size: smaller;'>(s)</sub>
  • C N<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub> + 3H<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub> → 2NH<sub style='font-size: smaller;'>3</sub><sub style='font-size: smaller;'>(g)</sub>
  • D 2HCI<sub style='font-size: smaller;'>(s)</sub> → H<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub> + CI<sub style='font-size: smaller;'>2</sub><sub style='font-size: smaller;'>(g)</sub>
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Question 5:
If an equilibrium reaction has ∆H < O, the reaction will proceed favorably in the forward reaction at?
  • A Low temperatures
  • B High temperatures
  • C All temperatures
  • D All pressures
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