Question

Compute the differences in masses of 1000 moles each of magnesium atoms and magnesium ions

Answer 1

Mass of 1 mol i.e. 6.023x10^23 =  24 g
Mass of 10^3 mole = 6.023x10^23 = 24 kg 

 Mg loses 2 electrons per atom hence no. of electrons lost are
= 6.023 x 10^23 x 2
= 1.2 x 10^27
 
Mass of 1 electron = 9.31 x 10^-31
 Therefore total mass of electrons lost = 1.2 x 10 x 9.31 x 10-31

difference in mass = 0.001121 kg
and mass of Mg ions = 24 - 0.001121 = 23.9989 kg

i hope it will help you
regards