How many moles of oxygen are in 123 g of Cr(SO4)3

Question

PLEASE SHOW THE WORK THOROUGHLY SO I CAN UNDERSTAND.

Answer 1

So, 1 MOLE of Cr(SO₄)₃ has the following in it;

1 mole of Cr

3 moles of S

12 moles of O

Hopefully you can see that. Everything inside the parentheses is multiplied by 3.

So, we need to find out how many moles of Cr(SO₄)₃ we have in the 123 g.

The molar mass of Cr(SO₄)₃ is 340.2 g / mol (add up the atomic masses of all of the elements)

123 g x 1 mol / 340.2 g = 0.3616 moles Cr(SO₄)₃

moles of O present = 0.3616 moles Cr(SO₄)₃ x 12 moles O / 1 mol Cr(SO₄)₃ = 4.34 moles of oxygen (3 s.f.)