Question

Number of moles of oxygen atom present in 0.1 moles ofAl2(do4)3

Answer 1

Al2(SO4)3 ??

in this molecule, you can see it has 3x4=12 atoms of Oxygen.

therefore, 1 mole of the compound will have 12 moles of O atoms

0.1 mole of the compound will have 1.2 moles of O atoms

;-)

Answer 2

1 mol Al2(SO4)3 contains 3*4 = 12 mol Oxygen

So 0.1 mole of Al2(SO4)3 would contain -

12 * 0.1 / 1 = 1.2 mole Oxygen