Question

25 POINTS!! Help! Using the table, which answer lists the salts in order of increasing solubility?

Salt: Ksp:
-----------------------------
PbSo4 = 1.6 x 10^-8
PbS = 8 x 10^-28
PbL2 = 7.1 x 10^-9
PbCl2 = 1.6 x 10^-5



PbCl2 < PbI2 < PbSO4 < PbS


PbS < PbI2 < PbSO4 < PbCl2


PbI2 < PbCl2 < PbS < PbSO4


PbS < PbI2 < PbCl2< PbSO4

Answer 1

Answer is: PbS < PbI2 < PbSO4 < PbCl2.

1) Chemical dissociation: PbSO₄(s) → Pb²⁺(aq) + SO₄²⁻(aq).
Ksp = 1.6·10⁻⁸.
[Pb²⁺] = [SO₄²⁻] = s; solubility.
Ksp = [Pb²⁺] · [SO₄²⁻].
s² = 1.6·10⁻⁸.
s = √1.6·10⁻⁸.
s = 1.26·10⁻⁴ M.
2) Chemical dissociation: PbS(s) → Pb²⁺(aq) + S²⁻(aq).
Ksp = 1.6·10⁻⁸.
[Pb²⁺] = [SO₄²⁻] = s; solubility.
Ksp = [Pb²⁺] · [SO₄²⁻].
s² = 8·10⁻²⁸.
s = √8·10⁻²⁸.
s = 2.83·10⁻¹⁴ M.
3) Chemical dissociation: PbI₂(s) → Pb²⁺(aq) + 2I⁻(aq).
Ksp = 7.1·10⁻⁹.
[Pb²⁺] = s; solubility.
[I⁻] = 2[Pb²⁺] = 2s.
Ksp = [Pb²⁺] · [I⁻]².
4s³ = 7.1·10⁻⁹.
s = ∛7.1·10⁻⁹ ÷ 4.
s = 1.2·10⁻³ M.
4) Chemical dissociation: PbCl₂(s) → Pb²⁺(aq) + 2Cl⁻(aq).
Ksp = 1.6·10⁻⁵.
[Pb²⁺] = s; solubility.
[Cl⁻] = 2[Pb²⁺] = 2s.
Ksp = [Pb²⁺] · [Cl⁻]².
4s³ = 1.6·10⁻⁵.
s = ∛1.6·10⁻⁵ ÷ 4.
s = 1.58·10⁻² M.