Question

What are the concentrations of hydroxide and hydronium ions in a solution with a pH of 4.6?

Answer 1

Answer : The concentration of hydroxide and hydronium ion is, $3.9\times 10^{-10}M$ and $2.5\times 10^{-5}M$

Explanation:  Given,

pH = 4.6

pH : It is defined as the negative logarithm of hydrogen ion and hydronium ion concentration.

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

First we have to calculate the $H^+$ concentration.

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

$4.6=-\log [H_3O^+]$

$[H_3O^+]=2.5\times 10^{-5}M$

Now we have to calculate the pOH.

$pH+pOH=14\\\\pOH=14-pH\\\\pOH=14-4.6=9.4$

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

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

$9.4=-\log [OH^-]$

$[OH^-]=3.9\times 10^{-10}M$

Therefore, the concentration of hydroxide and hydronium ion is, $3.9\times 10^{-10}M$ and $2.5\times 10^{-5}M$

Answer 2

Answer: 2.5 × 10⁻⁵ M H₃O⁺ and 4.0 × 10⁻¹⁰ M OH⁻

Explanation:

∵ pH = - log[H₃O⁺]

∴ 4.6 = - log[H₃O⁺].

∴ log[H₃O⁺] = - 4.6.

∴ [H₃O⁺] = 2.51 x 10⁻⁵.

∵ [H₃O⁺][OH⁻] = 10⁻¹⁴.

[H₃O⁺] = 2.51  x 10⁻⁵ M.

∴ [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(2.51  x 10⁻⁵ M) = 3.98 × 10⁻¹⁰ M ≅ 4.0 × 10⁻¹⁰ M.