Answer:
[OH⁻] = 1.77 × 10⁻¹¹ 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,
3.25 + pOH = 14
pOH = 14 - 3.25
pOH = 10.75
As ,
pOH = -log [OH⁻]
So,
[OH⁻] = 10^-pOH
Putting value of pOH,
[OH⁻] = 10⁻¹⁰·⁷⁵
[OH⁻] = 1.77 × 10⁻¹¹ M