# A sample of a compound contains 7.89 g potassium, 2.42 g carbon, and 9.69 g oxygen. What is the empirical and molecular formulas of this compound, which has a molar mass of 198.22 g/mol?

Dec 22, 2017

The empirical formula is $K C {O}_{3}$. The molecular formula is ${K}_{2} {C}_{2} {O}_{6}$

#### Explanation:

Let the molecular formula be ${K}_{m} {C}_{n} {O}_{p}$

The weight of the sample is

$m = 7.89 + 2.42 + 9.69 = 20 g$

The number of moles of each element is

Potassium $= \frac{7.89}{39.1} = 0.2$

Carbon $= \frac{2.42}{12} = 0.2$

Oxygen $= \frac{9.69}{16} = 0.6$

Divide by $0.2$

Potassium $= \frac{0.2}{0.2} = 1$

Carbon $= \frac{0.2}{0.2} = 1$

Oxygen $= \frac{0.6}{0.2} = 3$

Therefore,

The empirial formula is $K C {O}_{3}$

Since the molar mass is $= 198.22$

and

${M}_{K} + {M}_{C} + {M}_{O} = 39 + 12 + 3 \cdot 16 = 99$

The molecular formula is ${K}_{2} {C}_{2} {O}_{6}$

And the name of this compound is probably

Potassium peroxydicarbonate