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

Hint: 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.