how would you do this question

Question

when i did it i did -log(1.0) but that is just 0 so what it the procedure to do this question

Calculate the pH of a 1.0 mol/L aqueous solution of sodium benzoate. Note: Only the benzoate ion affects the pH of the solution.

Answer 1

Benzoate ion hydrolyzes in water to form a solution that is not neutral.
If we call the benzoate ion Bz^-, then
.........Bz^- + HOH ==> HBz + OH^-
I........1.0..............0.....0
C........-x..............x.....x
E.......1-x..............x......x

Kb for Bz^- = (Kw/Ka for HBz) = x*x/(1-x) and solve for x = (OH^-),then convert to pH.
HBz is benzoic acid. You can find Ka for HBz in you text/notes I'm sure but it's approx 10^-5.

Answer 2

thanks