Question

What is the empirical formula for a compound that is 31.9% potassium, 28.9% chlorine, and 39.2% oxygen?

Answer 1

The empirical formula is `KClO_3`, potassium chlorate.

Explanation:

In 100 g of stuff, there are 31.9 g potassium, 28.9 g of chlorine, and 39.2 g oxygen.

We divide these gram quantities by the respective atomic masses of each of the atoms to get the atomic ratio of constituents.

`K`: `(31.9*g)/(39.1*g*mol^-1)` `=` `0.816*mol`.

`Cl`: `(28.9*g)/(35.45*g*mol^-1)` `=` `0.816*mol`.

`O`: `(39.2*g)/(15.99*g*mol^-1)` `=` `2.45*mol`.

If we divide thru by the least molar quantity (that of potassium or oxygen), we get an empirical formula of `KClO_3`, potassium chlorate.

Note that because this is an ionic, and not a molecular species, we can quote the empirical as the actual formula.