Empirical Formula

Molecular Formula

The molecular formula of a compound represents the actual composition of a compound. It gives the kind and number of atoms of element present in the compound.

A molecular formula is either the same as the empirical formula or is a whole number multiple of it. You can find the multiple of it by dividing the given molecular mass by the molar mass of the empirical formula.

Example:

The Empirical formula of hydrazine is NH₂. The compound has a Molar Mass of 32g mol^-1. What is its molecular formula?

M(NH₂) = 16 g mol^-1- this is twice the molar mass of the molar mass - 16 x 2 = 32 g mol^-1.

So, the molecular formula is double the empirical formula- N₂H₄.

Empirical Formula Practice Questions

Molecular Formula Questions - look at the answers only after you've given the questions a go!