(a) What is a chemical formula ?

(b) What is the significance of a formula ? Give an example to illustrate.

(a) A chemical formula also known as molecular formula employs symbols to denote the molecule of an element or of a compound.

(b) The chemical/molecular formula of a compound has quantitative significance. It represents:

1. both the molecule and the molecular mass of the compound.
2. the respective numbers of different atoms present in one molecule of the compound.
3. the ratios of the respective masses of the elements present in the compound.

For example, the formula CO₂ means that:

1. the molecular formula of carbon dioxide is CO₂.
2. each molecule contains one carbon atom joined by chemical bonds with two oxygen atoms.
3. the molecular mass of carbon dioxide is 44, given that the atomic mass of carbon is 12 and that of oxygen is 16.