Question

Calculate the concentration of H3O⁺ in a solution that contains 5.5 × 10-5 M OH⁻ at 25°C. Identify the solution as acidic, basic, or neutral. A) 1.8 × 10-10 M, basic B) 1.8 × 10-10 M, acidic C) 5.5 × 10-10 M, neutral D) 9.2 × 10-1 M, acidic E) 9.2 × 10-1 M, basic

Answer 1

Answer : The correct option is, (A) $1.8\times 10^{-10}M$, basic.

Explanation : Given,

Concentration of $OH^-$ ion = $5.5\times 10^{-5}M$

First we have to calculate the pOH.

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

$pOH=-\log (5.5\times 10^{-5})$

$pOH=4.26$

Now we have to calculate the pH.

$pH+pOH=14\\\\pH=14-pOH\\\\pH=14-4.26=9.74$

Now we have to calculate the $H_3O^+$ concentration.

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

$9.74=-\log [H_3O^+]$

$[H_3O^+]=1.8\times 10^{-10}M$

As we know that, when the pH value is less than 7 then the solution acidic in nature and when the pH value is more than 7 then the solution basic in nature.

From the pH value, 9.74 we conclude that the solution is basic in nature because the value of pH is greater than 7.

Therefore, the $H_3O^+$ concentration is, $1.8\times 10^{-10}M$, basic.