Question

Calculate the concentrations of all species in a 1.23 M Na2SO3 (sodium sulfite) solution. The ionization constants for sulfurous acid are Ka1 = 1.4× 10–2 and Ka2 = 6.3× 10–8.

Answer 1

First you need to calculate the final pH

Since you are adding the conjugate base lets do de analysis as a base:

the mass action equation, remember since it is for the base is Kb and

At the equilibrium the concentration of the OH is equal to HSO₃^-

X=[OH]

C0=concentration added

Solving for X you get a quadratic equation that can be solved:

X=4.36x10^-4=OH

Remember

so H+=2.29x10-11

pH=10.64

Now using both mass action equations you can find the concentrations of the other compounds: