Question

Write the chemical formula of the following compound:

Sodium arsenite.

Answer 1

Chemical formula:

• The symbolic representation of a molecule of a compound is called its chemical formula.
• To write the formula of a chemical substance, the valency and the symbol of the various atoms or radicals present in it must be known.

For example, the chemical formula of sulphuric acid is ${\mathrm{H}}_2{\mathrm{SO}}_4$.

• The chemical formula of sodium arsenite is ${\mathrm{NaAsO}}_2$
• By applying the criss cross method:

$$\begin{gathered} \mathrm{Symbol}\mathrm{Na}{\mathrm{AsO}}_2 \\ \mathrm{Valency}1\nearrow \nwarrow 3 \end{gathered}$$

Therefore, the chemical formula for sodium arsenite is ${\mathrm{NaAsO}}_2$.