Question

What is the empirical formula for a sample of a compound that contains 60.0% sulfur and 40.0% oxygen?

Answer 1

Knowing molar mass of sulfur $M_S=32$ g/mole and oxygen $M_O=16$ g/mole, find number of gram-atoms:

$n=\tfrac{\omega}{M}$ ;

$n_S=\tfrac{60}{32}=1.875,$

$n_O=\tfrac{40}{16}=2.5.$

So

$n_S:n_O=1.875:2.5$ , or

$n_S:n_O=\tfrac{1.875}{1.875}:\tfrac{2.5}{1.875}=1:1.33$ .

Convert the ratio to whole number.

3 - that can multiplied with the numbers in atomic ratio.

$n_S:n_O=(1*3):(1.33*3)=3:4.$

The empirical formula: $S_3O_4$.

Answer: $S_3O_4.$