Question

What is the normality of $1\mathrm{M}{\mathrm{H}}_3{\mathrm{PO}}_4$ solution?

• A. $3.0\mathrm{N}$
• B. $2.0\mathrm{N}$
• C. $1.0\mathrm{N}$
• D. $0.5\mathrm{N}$

Answer 1

The correct option is A

$3.0\mathrm{N}$

Explanation for correct option

$\mathbf{\left(}\mathbf{A}\mathbf{\right)}$$3.0\mathrm{N}$

Step 1: Given,

$\mathrm{Molarity}=1\mathrm{M}$

Step 2: Formula used to determine the normality of the solution.

$\mathrm{Normality}=\mathrm{Molarity}\times \mathrm{n}-\mathrm{factor}$

Here,

$\mathrm{n}-\mathrm{factor}$ is the number of electrons gained or lost per atom during a reaction.

Step 3: To determine the $\mathrm{n}-\mathrm{factor}$ for ${\mathrm{H}}_3{\mathrm{PO}}_4$ solution.

On dissociation, phosphoric acid produces $3{\mathrm{H}}^{+}$ ions.

${\mathrm{H}}_3{\mathrm{PO}}_4\to 3{\mathrm{H}}^{+}+{\mathrm{PO}}_4^{3-}$

Thus, the n-factor for phosphoric acid, ${\mathrm{H}}_3{\mathrm{PO}}_4$​ is 3.

Step 4: To determine the normality of the solution.

$$\begin{gathered} \mathrm{Normality}=\mathrm{Molarity}\times \mathrm{n}-\mathrm{factor} \\ \mathrm{Normality}=1\times 3 \\ \mathrm{Normality}=3\mathrm{N} \end{gathered}$$

Explanation for incorrect options:

Since, the correct value of normality is $3\mathrm{N}$. Therefore, options (B), (C) and (D) stand incorrect.

Therefore, the correct option is $\mathbf{\left(}\mathbf{A}\mathbf{\right)}\mathbf{}\mathbf{3}\mathbf{.}\mathbf{0}\mathbf{}\mathbf{N}$.