[user456]

We have to calculate the pH of Ba(OH)₂ solution if 10ml of it neutralizes 20ml of 0.01 M HCl solution.
According to law of neutralization-
N_AV_A=N_BV_B
20×0.01=10×N_B
N_B=0.02
After that they calculate the pOH by taking the -logarithm of this normality. But isn't pOH the log of molarity of a base?
also in this case the molarity and normality would be different as there are 2 OH^- ions in one Ba(OH)₂ molecule.

[AWK]

But isn't pOH the log of molarity of a base?

You are right, but base in this case is OH- (normality of Ba(OH)₂ = molarity of OH-)

[Babcock_Hall]

The formula for pOH needs a minus sign in front of the log, but that's just me being picky.