Compute the difference in masses of 103 moles each of magnesium atoms and magnesium ions.
(Mass of an electron = 9.1×10–31 kg)
A Mg atom and Mg2+ ion differ by two electrons.
For 103 moles, each of magnesium atoms and ions there would be a difference of 103 x 2 moles of electrons.
Mass of 2 ×103 moles of electrons = 2×103 × 6.023 ×1023 × 9.1 ×10–31 kg
= 2 × 6.022 × 9.1 × 10–5kg = 109.6004 ×10–5 kg
= 1.096 × 10–3kg