What is the pH of 1.0M Na2SO3 (aq)solution at 25C?

a) 3.40
b) 6.03
c) 10.60
d) 7.96
e) 10.40
How can I get ph from only the Molarity?

1 answer

The pH is determined by the hydrolysis of the salt.
........SO3^2- + HOH ==> HSO3^- + OH^-
initial..1.0.............0.........0
change...-x..............x.........x
equil...1-x..............x.........x

Kb for SO3^2- = (Kw/k2 for H2SO3) = (HSO3^-)(OH^-)/(SO3^2-)
Substitute and solve for x = (OH^-) and convert to pH. k2 for H2SO3 in my text (an old one so look in your text for an up to date value) is 6.43E-8.