Question

A solution at 25 degrees Celsius is 1.0 × 10–5 M H3O+. What is the concentration of OH– in this solution? 1.0 × 10–5 M OH– 1.0 × 10–14 M OH– 1.0 × 105 M OH– 1.0 × 10–9 M OH–

Answer 1

Answer:

1.0 × 10⁻⁹ M.

Explanation:

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

[H₃O⁺] = 1.0 x 10⁻⁵ M.

∴ [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(1.0 x 10⁻⁵ M) = 1.0 × 10⁻⁹ M.

Answer 2

Answer : The correct option is, $1.0\times 10^{-9}M$ $OH^-$

Explanation:

First we have to calculate the pH.

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

$pH=-\log (1.0\times 10^{-5})$

$pH=5$

Now we have to calculate the pOH.

$pH+pOH=14\\\\pOH=14-pH\\\\pOH=14-5=9$

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

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

$9=-\log [OH^-]$

$[OH^-]=1.0\times 10^{-9}M$

Therefore, the $OH^-$ concentration is, $1.0\times 10^{-9}M$