# How do you calculate the percentage composition by mass of potassium in potassium hydroxide?

Jan 25, 2017

Add the up the atomic masses of all the atoms in the compound to find the molecular mass. Then divide the mass of potassium present in the molecule by the molecular mass of the molecule.

#### Explanation:

K (potassium) = 39 amu
O ( oxygen) = 16 amu
H ( hydrogen) = 1

The total mass of the compound is 56 amu or 56 grams/mole

The percentage of potassium =  39/56 xx 100 = 70%