A solution has a ph of 10.20 at 25°c. what is the hydroxide-ion concentration at 25°c?

Using equation:

pH+pOH=14

We are given pH=10.20 at 25°c.

So putting this value in the equation,

We have pOH=14-10.20

= 3.8

pOH=-log (OH)

-log (OH) = 3.8

OH=0.00015M

So hydroxide concentration will be 0.00015 M.