Question

The pH ${\text{0}}{\text{.1M NaCl }}$solution at ${\text{2}}{{\text{5}}^{\text{o}}}{\text{C}}$is
(A) 1
(B) 13
(C) 7
(D) Zero

Answer 1

pH is the value that expresses the acidity or alkalinity of a solution on a logarithmic scale. If the pH is 7, this means that the solution is neutral. If pH ${\text{ < 7}}$ the solution is acidic whereas if the ${\text{ph > 7}}$ the solution is alkaline or basic.

Complete step by step answer:
When a strong acid and a strong alkali or base combine, it forms a neutral salt i.e., having pH = 7. The reaction of the formation of ${\text{NaCl}}$ is –
${\text{NaOH + HCl }} \to {\text{NaCl + }}{{\text{H}}_{\text{2}}}{\text{O}}$
Since sodium chloride ${\text{NaCl}}$ is neutral, it does not affect the ${\text{[}}{{\text{H}}^{\text{ + }}}{\text{]}}$ and ${\text{[O}}{{\text{H}}^ - }{\text{]}}$ in water and the concentration of ${\text{NaCl}}$ solution does not alter the pH of the solution. Therefore, the pH is 7.
Thus, the pH of ${\text{0}}{\text{.1M NaCl }}$ solution at ${\text{2}}{{\text{5}}^{\text{o}}}{\text{C}}$ is 7.

Hence, the correct answer is (C) i.e., 7

Note: The difference between acid, base and salt should be cleared. Sodium chloride or ${\text{NaCl}}$ is a salt that is formed by the reaction of sodium hydroxide (${\text{NaOH}}$) and hydrochloric acid (${\text{HCl}}$). Here, ${\text{NaOH}}$ is a strong base and ${\text{HCl}}$ is a strong acid. This results in ${\text{NaCl}}$ being formed that is a salt.