Question

Calculate the concentrations of H₂C₂O₄, HC₂O₄⁻, C₂O₄²⁻, and H⁺ species in a 0.370 M oxalic acid solution (K_a1 = 6.5 ×10⁻², K_a2 = 6.1 ×10⁻⁵). Be sure to report your answers to the correct number of significant figures.

Answer 1

H2C2O4   ---------------> HC2O4-   + H+

0.370                                  0              0

0.370 - x                            x              x

Ka1 = x^2 / 0.370 - x

6.5 x 10^-2 = x^2 / 0.370 - x

x = 0.126

[HC2O4-] = 0.126 M

[H+] = 0.126 M

[H2C2O4] = 0.244 M

[A2-] = 6.10 x 10^-5 M