one mol of Mg in vapour state absorbed 1200 KJ energy. If the first and 2^nd ionisation enthalpies of Mg r 750 and 1450 KJ mol^-1 respectively, the final composition of the mixture is

1. 69% Mg+, 31% Mg2+
2. 59% Mg+,41% Mg2+
3. 49% mg+ 51 mg 2+
4. 29 mg+ 71% mg2+

it’s answer is (1).
as this ionisation is an endergonic or energy-absorbing process andIst IP < IInd IP < IIIrd IP because as the electrons go out of the atom, the ionic size goes on decreasing and the amount of positive charge goes on increasing because of which positive charge contibution goes on decreasing in the final composition as the atomic size also decreases.