Question

A sample of an iron sulfide contains `2.561*g` of metal, and `2.206*g` of sulfur. What is the empirical formula of iron sulfide?

Answer 1

`Fe_2S_3`

Explanation:

`"Moles of iron"` `=` `(2.561*g)/(55.85*g*mol^-1)` `=` `0.0459*mol`

`"Moles of sulfur"` `=` `(2.206*g)/(32.06*g*mol^-1)` `=` `0.0688*mol`

If we divide thru by the lower molar quantity, we get, `FeS_(1.5)`. However, by definition, the empirical formula is the simplest WHOLE number that defines constituent elements in a species, so we double the formula to get WHOLE numbers:

`Fe_2S_3`.