Compute the difference in masses of one mole each of aluminium atoms and one mole of its ions. (Mass of an electron is 9.1x10-28 g). Which one is heavier?
Mass of 1 mole of aluminium atom = the molar mass of aluminium = 27 g mol-1
An aluminium atom needs to lose three electrons to become an ion, AI3+
For one mole of AI3+ ion, three moles of electrons are to best lost.
The mass of three moles of electrons 3 x (9.1x10-28) x 6.022 x1023 g
= 27.3 x 6.022 x10-5 g
=164.400 x 105 g
=.00164 g
Molar mass of Al3+ = (27 - 0.00164) gmol-1
= 26.998gmol-1
Difference = 27 – 26.9984 = 0.0016 g
