# An unknown compound was found to have a percent composition as follows 47.0% potassium, 14.5% carbon, and 38.5% oxygen. What is its empirical formula?

Jan 2, 2016

Potassium oxalate?

#### Explanation:

In 100 g of compound there are 47.0 g potassium, 14.5 g carbon, and 38.5 g oxygen. Why?

We divide thru by the atomic masses:

$K$ $=$ $\frac{47.0 \cdot g}{39.1 \cdot g \cdot m o {l}^{- 1}}$ $=$ $1.20$.

$C$ $=$ $\frac{14.5 \cdot g}{12.0 \cdot g \cdot m o {l}^{- 1}}$ $=$ $1.21$.

$O$ $=$ $\frac{38.5 \cdot g}{16.0 \cdot g \cdot m o {l}^{- 1}}$ $=$ $2.4$.

Now if we divide thru by the lowest ratio, we get ${K}_{n} {C}_{m} {O}_{o}$ $=$ $K C {O}_{2}$ as the empirical formula.

You have likely got the dipotassium salt of oxalic acid, $H O C \left(= O\right) C \left(= O\right) O H$, which has precisely this empirical formula. I take it you are an undergraduate?