At 298 K the enthalpy of formation of liquid water is -285.9 kJ/mol and that of steam -242.8 kJ/mol. The enthalpy of vapourisation of water is

Options

(a) 43.1 kJ/mol
(b) -43.1 kJ/mol
(c) 242.8 kJ/mol
(d) -242.8 kJ/mol

Correct Answer:

43.1 kJ/mol

Explanation:

ΔH(vap) = -242.8 – (-285.9) = 43.1 kJ/mol.