What is the mass fraction of oxygen in calcium hydroxide Ca (OH) 2?

The mass fraction of an element in a compound is defined as the ratio of the sum of the relative atomic mass of all atoms of this element in the composition of a substance to the relative molar mass. The formula can be represented as:

ω = (n * Ar) / Mr

The relative molecular weight is found as the sum of the relative atomic masses (RAM) of all the elements in a compound. OAM is taken from the periodic table.

Ar (O) = 16

Mr (Ca (OH) 2) = Ar (Ca) + Ar (O) * 2 + Ar (H) * 2 = 40 + 16 * 2 + 1 * 2 = 74.

Let’s find the mass fraction of oxygen:

ω (O) = (2 * 16) / 74 = 0.43.

Answer: the mass fraction of oxygen is 0.43.