In: Chemistry
What is the pH of a 0.39 M solution of sodium oxalate, Na2C2O4? Acid ionization constants for oxalic acid are Ka1 = 5.6 x 10-2 and Ka2= 5.4 x 10-5.
C2O4^2- + H2O -----------------------> HC2O4- + OH-
0.39 0 0
0.39 - x x x
Kb2 = [HC2O4-][OH-] / [C2O4^2-]
Kw / Ka2 = x^2 / (0.39 - x)
1.0 x 10^-14 / 5.4 x 10-5.= x^2 / (0.39 - x)
1.85 x 10^-10 = x^2 / (0.39 - x)
x = 8.5 x 10^-6
[OH-] = 8.5 x 10^-6 M
pOH = -log[OH-] = -log (8.5 x 10^-6 )
= 5.07
pH + pOH = 14
pH = 14 - 5.07 = 8.9
pH = 8.93