[carlsone]

Pb(s) + PbO₂(s) + 4H⁺(aq) + 2SO₄^2–(aq) ⇌ 2PbSO₄(s) +  2H₂O(ℓ)


Assuming equilibrium has been established, which one of the following will cause a
decrease in pH?
(a) adding more solid lead
(b) adding solid sodium sulfate
(c) removing solid lead sulfate
(d) adding barium nitrate solution

I am assuming that any addition or removal of solids will not impact on the hydrogen ion concentration and therefore equilibrium. Unless they can alter the concentration. Is (d) the answer then? Because water in the nitrate solution dilutes the system which in turn reestablishes the concentration by increase the amount of hydrogen ion?  I'd appreciate any input, thanks.

[mjc123]

What happens when you have barium and sulfate ions in solution?

[carlsone]

I see so you're saying that Barium Sulfate will be formed, the system will re-establish the concentration of sulfate ion and in doing so will re-establish the concentration of reactant species?

[mjc123]

Yes

[carlsone]

Thanks for that, but I'm wondering, it doesn't directly explain how hydrogen ion concentration increases, as it would if a base was added to the system, that's
 where my confusion lies.

[AWK]

Think about electroneutrality of solution.

[carlsone]

That's  really helpful, thank you both.  I was confining myself to acid/base and equilibrium concepts.