Question

1st and 2nd ionization energies of magnesium are 7.645 and 15.035 eV respectively. The amount of energy in kJ needed to convert all the atoms of magnesium into Mg²⁺ ions present in 12 mg of magnesium vapours in

Answer 1

7.645 eV = 1.224 x 10 ^-18 J/mol
15.035 eV = 2.4 x 10^-18 J/mol

Molar mass Mg = 24 g/mol
Number of moles in 12 mg (12 x 10^-3 g) of magnesium = (12 x 10^-3 ) / 24
= 5 x 10^-4

Energy required to convert 1 mole of magnesium atoms into Mg²⁺ ions = (1.224 +2.4) x 10^-18 J
= 3.624 x 10^-18 J
So, energy required to convert 5 x 10^-4 mole of magnesium atoms into Mg²⁺ ions = 3.624 x 10^-18 x 5 x 10^-4
= 1.81 x 10^-21 J