Question

Find the $pH$ of $N{a_2}S{O_4}$:
A) $7$
B) $> 7$
C) $< 7$
D) Data insufficient.

Answer 1

We know that $pH$ is the concentration of hydrogen ion in the solution.
The mathematical expression of $pH$ is,
$pH = \log \left[ {{H^ + }} \right]$
A solution which has $pH$ less than seven then is considered as acidic and a solution which has $pH$ greater than seven then it is considered as basic.

Complete step by step answer:
First, we see the preparation of sodium sulphate.
Sodium sulphate is formed by the reaction of sodium hydroxide and sulphuric acid.
$2NaOH + {H_2}S{O_4}\xrightarrow{{}}N{a_2}S{O_4} + 2{H_2}O$
The above reaction is the reaction between strong acid and strong base.
We know that sulphuric acid is a strong acid and sodium hydroxide is a strong base.
Sulphuric acid provides hydrogen ion which combines with the hydroxyl ion from the strong base to form water molecules leading to $pH$ of $7$ and the anion of the acid combines with cation of the base to give a neutral salt.

Thus, an option A is correct.

Additional Information:
We know that a strong acid and strong base ionizes completely in aqueous solution. The general equation of the dissociation of acid is,
$HA\left( {aq} \right)\xrightarrow{{}}{H^ + }\left( {aq} \right) + {A^ - }\left( {aq} \right)$
The general equation for the dissociation of base is,
$XOH\left( {aq} \right)\xrightarrow{{}}{X^ + }\left( {aq} \right) + O{H^ - }\left( {aq} \right)$
The $pH$ range of the body is$7 - 7.8$. If the $pH$ of rain water is less than $5.6$ then it is called acid rain. When acid rain flows into the river it lowers the $pH$ of water and the survival of aquatic life in such a reaction is difficult.

Note:
We must know that if ${\text{pOH}}$ value is given then the ${\text{pH}}$ of the solution is also calculated from the value of ${\text{pOH}}{\text{.}}$ the formula to calculate the ${\text{pH}}$ of the solution is,
${\text{pOH + pH = 14}} \\\ {\text{pH = 14 - pOH}} \\\$