Question

What is the formula mass for sulphur dioxide?

Answer 1

If the formula of sulphur dioxide is $S{O}_2$ the first step is to find the the molar mass of each elements present.

Sulphur dioxide has sulphur (S) and oxygen (O) present. If you refer to your periodic table, the atomic weight equals to the molar mass.

The molar mass of sulphur is 32.1 g/mol, and oxygen is 16.0 g/mol.

If you look back at the formula $\left(S{O}_2\right)$, you can see that there is one sulphur and two oxygens present.

Therefore, the molar mass of sulphur dioxide is $[1\times 32.1+2\times 16.0]=64.1$ g/mol.