For which salt in each of the following groups will the solubility depend on pH?

Pb(OH)2
PbCl2

could you explain too?
thanks!

You are working with (H^+)(OH^-) = Kw = 1E-14. This is the ion product of water which is a constant of 1E-14. So Pb(OH)2 will be the one that is pH depended BECAUSE that is the one with OH^- in it. As you change the pH, you are changing the H^+ (of course) so the OH must change, too. I think it is simpler to look at it as a Le Chatelier's Principle problem.

Pb(OH)2(s) ==> Pb^2+ + 2OH^-
Now, what happens as I increase H^+. That reacts with OH to form water and shifts the reaction to the right which has the effect of increasing the solubility of Pb(OH)2.

To identify whether the solubility of a salt depends on pH, we need to consider if the salt has a basic or acidic component that can undergo hydrolysis.

1. Pb(OH)2:
In this case, Pb(OH)2 is a salt that contains the hydroxide ion (OH-) group. Hydroxide ions are basic in nature and can react with water to form hydroxide ions (OH-) and hydronium ions (H3O+). This hydrolysis reaction can be represented as:
Pb(OH)2 + H2O ⇌ Pb(OH)+ + OH-
The reaction generates hydroxide ions, which increases the concentration of OH- in the solution. As a result, the solubility of Pb(OH)2 will be pH-dependent and increase in alkaline or basic conditions.

2. PbCl2:
In the case of PbCl2, it does not contain any component that can undergo hydrolysis and release ions upon reaction with water. PbCl2 remains relatively insoluble in water and does not depend on pH for its solubility. The solubility of PbCl2 generally remains constant regardless of the pH of the solution.

Therefore, for the given salts, the solubility of Pb(OH)2 will be pH-dependent, whereas the solubility of PbCl2 will not be affected by pH.