One mole of magnesium in the vapour state absorbed 1200 kJ mol–1 of energy. If the first and second ionisation energies of Mg are 750 and 1450 kJ mol–1 respectively, the final composition of the mixture is
(a) 31% Mg+ + 69% Mg2+
(b) 69% Mg+ + 31% Mg2+
(c) 86% Mg+ + 14% Mg2+
(d) 14% Mg+ + 86% Mg2+