Question

What percentage of the total mass of the compound `KAl_2S_2O_3` is due to the sulfur in the compound?

Answer 1

The sulfur accounts for 31.3 % of the mass of the compound.

Explanation:

You must determine two values:

1. The molar mass of the compound - for `KAl_2S_2O_3` this is 39.1 + (2 x 27.0) + (2 x 32.1) + (3 x 16.0) = 205.3 g

2. The mass of the requested element in this formula. In this case, each formula unit contains two sulfur atoms, so the mass is 64.2 g

Divide 2 by 1:

`64.2/205.3 = 0.313` or 31.3 %