Question

Write the chemical formulae for the following compounds :

(i) Sulphuric acid :

(ii) Nitric acid :

(iii) Potassium nitrate :

(iv) Sodium chloride :

(v) Sodium bicarbonate :

(vi) Aluminium chloride :

Answer 1

• A chemical formula is a representation of a substance's molecular composition in terms of the symbols for the elements that make up the molecule.
• Water is a substance with two hydrogen atoms and one oxygen atom in each molecule. ${\mathrm{H}}_2\mathrm{O}$ is the formula for water.
• A chemical formula of a compound is obtained by using the criss-cross method, where the valencies of both positively and negatively charged ions in interchanged in such a way to get a neutral compound.

Sulphuric acid $$\begin{gathered} \mathrm{H}{\mathrm{SO}}_4 \\ +1-2 \\ \overline{{\mathrm{H}}_2{\mathrm{SO}}_4} \end{gathered}$$	Nitric acid $$\begin{gathered} \mathrm{H}{\mathrm{NO}}_3 \\ +1-1 \\ \overline{{\mathrm{HNO}}_3} \end{gathered}$$	Potassium nitrate $$\begin{gathered} \mathrm{K}{\mathrm{NO}}_3 \\ +1-1 \\ \overline{{\mathrm{KNO}}_3} \end{gathered}$$
Sodium chloride $$\begin{gathered} \mathrm{Na}\mathrm{Cl} \\ +1-1 \\ \overline{\mathrm{NaCl}} \end{gathered}$$	Sodium bicarbonate $$\begin{gathered} \mathrm{Na}{\mathrm{HCO}}_3 \\ +1-1 \\ \overline{{\mathrm{NaHCO}}_3} \end{gathered}$$	Aluminium chloride $$\begin{gathered} \mathrm{Al}\mathrm{Cl} \\ +3-1 \\ \overline{{\mathrm{AlCl}}_3} \end{gathered}$$