In a sample of hydrogen atom containing 1 mole of H atoms, electrons in 30% of H-atoms are in `1^"st"` excited state and remaining are in `2^"nd"` excited state and ground state . If the total energy emitted when all electrons return to ground state is 642.24 kJ, find % of electron in `2^"nd"` excited state . Energy level in H-atom =`E_1=-13.6 eV, E_2=-3.4 eV, E_3= -1.5 eV` and (1 eV/ species =96 kJ /mole)

Answer

30