WAEC Chemistry 2014 Objective — Question 32

Question 32 of 50 from the West African Examinations Council (WAEC) Chemistry 2014 Objective paper, with the correct answer and a full explanation.

Consider the following energy profile diagram of exothermic reaction. The enthalpy change, ΔH is

A. +40 kJmol⁻¹
B. −40 kJmol⁻¹Correct
C. +80 kJmol⁻¹
D. −80 kJmol⁻¹

Explanation

From the diagram, reactants are at about 80 kJ/mol and products at about 40 kJ/mol. Since the reaction is exothermic (energy released), ΔH = products − reactants = 40−80 = −40 kJmol⁻¹.

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