The ionization enthalpies of Li and Na are 520 kJ m o l - 1 and 495 kJ m o l - 1 respectively. The energy required to convert all the atoms present in 70 mg of Li vapours and 230 mg of sodium vapours of their respective gaseous cations respectively are

Step-by-step solution

Number of moles = w e i g h t in gm atomic weight Number of moles Li = 70 1000 × 7 = 10 - 2 Number of moles of Na = 230 1000 × 23 × = 10 - 2 Amount of energy = moles × energy needed for 1 mole. So the amounts of energies required for 1 0 - 2 mole each of Li and Na are as follows For sodium = 520 × 10 - 2 kJ = 5200 J For Lithium = 495 × 10 - 2 kJ = 4950 J respectively.