Question

What are the concentrations of hydroxide and hydronium ions in a solution with a pH of 10.2?

Answer 1

Answer: The correct option is, (D) $6.3\times 10^{-11}M$  and $1.6\times 10^{-4}$

Explanation:  pH is the measure of acidity or alkalinity of a solution.

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

$10.2=-\log [H^+]$

$[H^+]=6.30\times 10^{-11}$

Now we have to calculate the concentration of $OH^-$ ions.

$pH+pOH=14\\\\pOH=14-pH\\\\pOH=14-10.2=3.8$

Now we have to calculate the $OH^-$ concentration.

$pOH=-\log [OH^-]$

$3.8=-\log [OH^-]$

$[OH^-]=1.6\times 10^{-4}M$

Therefore, the $H^+$ concentration is $6.3\times 10^{-11}$and $OH^-$ concentration is, $1.6\times 10^{-4}M$

Answer 2

Answer;

6.3 × 10–11 M H3O+ and 1.6 × 10–4 M OH–

Explanation;

pH = -log [H3O+]

Therefore;

if pH is 10.2; then;

[H3O+] = -in(pH)

           = 10^-10.2

          =6.3 × 10–11 M H3O+

But; pH + pOH = 14

Therefore;

pOH = 14 - 10.2

        = 3.8

But; pOH = -log [OH-]

[OH] = In pOH

        = 10^-3.8

        = 1.6 × 10^-4 M OH-