Question

Determine the molar solubility of PbSO4 in pure water. Ksp (PbSO4) = 1.6 × 10-10.

a) 4.12 × 10-5 M

b) 1.35 × 10-4 M

c) 4.89 × 10-4 M

d) 1.26 × 10-5 M

e) 1.28 × 10-8 M

Answer 1

Lets see the equilibrium reaction of PbSO₄ to calculate molar solubility

PbSO₄  $\rightleftharpoons$ Pb²⁺_(aq) + 2SO₄^2-_(aq)  

As we can see , every one mole of PbCl₂ produces 1 mole of Pb²⁺ and 1 mole of SO₄^-

Lets see the ICE table

PbSO₄$\rightleftharpoons$ Pb²⁺_(aq) + SO₄^2-_(aq)  

Initial - 0 0

Change - +s +s

at Equilibrium - s s

So, Solubility product constant for above reaction is

Ksp = [Pb²⁺][SO₄^2-] = (s) (s) = s²

Ksp = s²

Then

s² = Ksp = 1.6 $\times$ 10^-10

lets take square root on both the sides

we get

s = 1.26 $\times$ 10^-5 M

So option (d) is correct