Question

compute the difference in masses of one mole each of aluminium atoms and one mole of its ions . (mass of an electron is 9.1 x 10^-28 g ) . which one is more heavier ?

Answer 1

Mass of 1 mole of aluminium atom is = Molar mass of aluminium = 27 g mol​-1

Aluminium atom has to lose three electrons to form Al³⁺ ion.
Three moles of electrons will be lost to form 1 mole of Al^{3 +} ion.
Mass of electron = 9.1$\times$×10^-28 g
Hence , the mass of three moles of electrons = 3 $\times$×9.1×$\times$ 10^-28 $\times$×6.022 $\times$×10²³ g
= 27.3 $\times$×6.022 $\times$×10^-5 g
= 0.00164 g
Therefore , the molar mass of Al^{3 +} = (27 - 0.00164 ) g mol^-1 = 26.9983 g mol^​-1
Hence , aluminium atom is heavier than Al³⁺ ion.
Difference : 27 - 26.9983 = 0.0017 g