A certain manganese oxide contains 72% manganese. What is the empirical formula?

1 Answer
May 1, 2017

Since % litterally means "per hundred" let's take a 100g sample.

Explanation:

We convert the mass ratio into mol ratio:

Then 72g of this is Manganese.
The molar mass of Mn=55, so 72g7255=1.31mol of Mn

The 28g of Oxygen (molar mass O=16) breaks down to:
28g2816=1.75mol of O

The mol ratio Mn÷O=1.31÷1.75=0.75÷1=3÷4

Empirical formula: Mn3O4

Note:
This works if you take any other sample size, but then there are more calculations to do.