Question

What is the % composition of copper in a compound that contains 43.40 g of copper and 10.95 g of sulfur?

Answer 1

Let us start by determining the compound formula.

We have Cu^1+ and S^2- when you use a criss cross method, these give you Cu2S.

The molar masses of:

Cu = 63.55 g/mol

S = 32.07 g/mol

Cu2S = 159.17 g/mol

We will use the molar mass and the masses given to calculate the percentage of S and Cu.

For Cu:

(43.40/159.17) x100 = 27.3%

For S:

(10.95/159.17) x 100 = 6.9%