Question

The normality of $0.3\text{m}$ phosphorous acid is ___?

Answer 1

Step1. Phosphorous acid

• The chemical name of ${\mathrm{H}}_3{\mathrm{PO}}_3$is phosphorus acid.
• Only those $\text{H}$ atoms which are attached with oxygen in $\mathrm{P}–\mathrm{OH}$ form are ionizable and cause the basicity.

• Only two $\text{H}$ atoms are attached with oxygen in $\mathrm{P}–\mathrm{OH}$ in case of phosphorous acid.
• Hence, basicity is two.

Step2. Formula for normality

$\text{Normality = molarity×basicity (for acids)}$

Step3. Calculation of normality

$$\begin{gathered} \text{Normality = 0.3×2} \\ =0.6\text{N} \end{gathered}$$

Hence, the normality of $0.3\text{m}$ phosphorous acid is $0.6\text{N}$.