Question

Which equation correctly shows how you could calculate [OH-] from [H+]

Answer 1

Answer:

[OH⁻] = 10⁻¹⁴/[H⁺].

Explanation:

∵ [H⁺][OH⁻] = 10⁻¹⁴.

∴ [OH⁻] = 10⁻¹⁴/[H⁺].

Answer 2

Answer:

$Kw = [H+][OH-]$

Explanation:

For a given solution H+ refers to the hydrogen ion concentration and is indicative of the acidity of the solution. The more the [H+] concentration, higher is the acidity. Similarly, OH- refers to the hydroxide ion concentration and reflects the basicity of the solution. A solution with a higher OH- concentration is said to be basic.

The two are related by considering the dissociation of water:

$H2O(l)\rightleftharpoons H+(aq)+ OH-(aq)$

The dissociation constant for water, Kw is:

$Kw = [H+][OH-]\\\\where\ Kw = 10^{-14} \\\\10^{-14} = [H+][OH-]$

$[H+] = \frac{10^{-14}}{[OH-]}$