Calculate the ph of a 0.005 m solution of potassium oxide k2o

First, we have to see how K2O behaves when it is dissolved in water:

K2O + H20 = 2 KOH

According to reaction K2O has base properties, so it forms a hydroxide in water.

For the reaction next relation follows:

c (KOH) : c (K2O) = 1 : 2

So,

c (KOH) = 2 x c (K2O) = 2 x 0.005 = 0.01 M = c (OH⁻)

Now we can calculate pH:

pOH = - log c (OH⁻) = - log 0.01 = 2

pH = 14-2 = 12