To determine the solubility product of copper(II) iodate, Cu(IO3)2, by iodometric titration in an ac — Physical Chemistry — Kinetics Chemistry Question
Solubility Product of Copper(II) Iodate
To determine the solubility product of copper(II) iodate, Cu(IO3)2, by iodometric titration in an acidic solution (25 °C) 30.00 cm3 of a 0.100 molar sodium thiosulphate solution are needed to titrate 20.00 cm3 of a saturated aqueous solution Cu(IO3)2.
Write the sequence of balanced equations for the above described reactions.
Model Answer
2 Cu2+ + 4 IO3- + 24 I- + 24 H+ → 2 CuI + 13 I2 + 12 H2O (1)
I2 + 2 S2O32- → 2 I- + S4O62- (2)
Calculate the initial concentration of Cu2+ and the solubility product of copper(II) iodate. Activity coefficients can be neglected.
Model Answer
From (2):
n(S2O32-) = c V = 0.100 mol dm-3 × 0.03000 dm3 = 3.00×10-3 mol
From (2) and (1):
n(I2) = 1.50×10-3 mol
n(Cu2+) = 1.50×10-3 mol × 2 / 13 = 2.31×10-4 mol
c(Cu2+) = 2.31×10-4 mol / 0.02000 dm3 = 1.15×10-2 mol dm-3
[Cu2+] = 1.15×10-2
[IO3-] = 2 [Cu2+]
Ksp = [Cu2+] [IO3-]2 = 4 [Cu2+]3 = 4 × (1.15×10-2)3 = 6.08×10-6