Question

What is the pH of a solution with a concentration of 4.2 × 10–5 M H3O+?

Answer 1

Answer;

pH = 4.38

Explanation;

Consider that;

[H3O+] = 10-pH mol/L

 Therefore; the pH is the -log of the [hydronium ion].

pH = - log [H3O+]

Thus;

pH = - log (4.2 × 10^–5)

     = 4.38

Answer 2

Answer : The correct option is, 4.38

Explanation : Given,

concentration of $H_3O^+$ = $4.2\times 10^{-5}M$

pH : It is defined as the negative logarithm of hydrogen ion $(H^+)$ or hydronium ion $(H_3O^+)$ concentration.

Formula used :

$pH=-\log [H_3O^+]$

$pH=-\log (4.2\times 10^{-5})$

$pH=4.38$

Therefore, the pH of a solution is, 4.38