A solution containing 0.1238 mol Na2C2O4 and 0.0176 mol NaHC2O4 was treated with 23.58 mL of a 0.766 M HCl solution and diluted to 1.00 L. the solution pOH was fond to be 9.32. determine Ka2 for oxalic acid or Kb1 for the oxalate ion.
moles of HCl added = 23.58 x 0.766 / 1000 = 0.01806
C2O42- + HCl ----------------> HC2O4-
0.1238 0.01806 0.0176 ----------------> initial
- 0.01806 - 0.01806 +0.01806 --------------> Change
0.14186 0 0.03566 --------------> equilibrium
pOH = 9.32
pH = 14 - 9.32 = 4.68
pH = pKa2 + log [salt - C / acid + C]
4.68 = pKa2 + log [0.1238 - 0.01806/ 0.0176 + 0.01806]
pKa2 = 4.2079
Ka2 = 6.20 x 10^-5
Kb1 = 10^1-14 / 6.12 x 10^-5
Kb1 = 1.61 x 10^-10
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