Assume that acid rain has lowered the ph of a particular lake to ph 4.0. What is the hydroxyl ion concentration of this lake?

[OH⁻] = 1.0 * 10⁻¹⁰ M

Solution:

In order to calculate concentration of hydroxide ion i. e. [OH⁻] first we will find the pOH by using following relation,

pH + pOH = 14

Putting value of pH given and solving for pOH,

4.0 + pOH = 14

pOH = 14 - 4.0

pOH = 10.0

As,

pOH = - log [OH⁻]

So,

[OH⁻] = 10^-pOH

Putting value of pOH,

[OH⁻] = 10⁻¹⁰

[OH⁻] = 1.0 * 10⁻¹⁰ M