In which of the solutions will Lead sulfate, PbSO4, be most soluble in? Explain. (a) pure water (b) 0.05M NaNO3 (c) 0.05M Na2SO4 (d) 0.05M Pb(NO3)2

Answer 1

Looking at the solubility of PbSO₄, we can write it as ...

PbSO₄(s) <==> Pb²⁺(aq) + SO₄^2-(aq) ... this would be in pure water (a)

For (b), NaNO₃:

Adding Na⁺ and NO₃^- ions would form Pb(NO₃)₂ and Na₂SO₄ by reacting with the Pb²⁺(aq) and SO₄^2-(aq). But since both of these dissociate completely, this would have no effect on the solubility of PbSO₄

For (c), Na₂SO₄:

Adding a common ion (SO₄^2-) will, according to Le Chatelier's Principle, push the reaction toward the reactant side thus decreasing the solubility of PbSO₄

For (d), Pb(NO₃)₂:

Again, adding a common ion (Pb²⁺) will decrease the solubility of PbSO₄ (see reason for c).

So, in summary, PbSO₄ would be most soluble in pure water and in the NaNO₃ solution.