Question

Will the heat release in the following two reactions be equal? Give reasons in support of your answer:

(i) H2 (g) + 1/2 O2 (g) → H2O (g)

(ii) H2 (g) + 1/2 O2 (g) → H2O (l)

Answer 1

No, The heats released in the two reactions are not equal. The heat released in any reaction depends upon the reactants, products and their physical states. Here in reaction (i) the water produced is in the gaseous state whereas in reaction (ii) liquid water is formed. As we know, that when water condenses to form water, heat equal to the latent heat of vaporisation is released. Thus, more heat is released in reaction (ii).