Mr Study's 3/4 Questions

[Mr. Study]

How would I do this question?

A 15.00 g sample of an unstable hydrated salt, Na₂SO₄.xH₂O was found to contain 7.05 g of water. The value of x in this formula is?

Thanks.

[oliverk94]

m of Na₂SO₄ = 15 - 7.05 = 7.95 g

n(Na₂SO₄):n(xH₂O)

7.95/142 g mol: 7.05/18 g mol

0.05598: 0.391667

Divide by smallest value

0.05598/0.05598: 0.391667/0.05598

1: 7

So the equation will be:
Na₂SO₄:7H₂O

x=7

[Mr. Study]

Thank you for that!