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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: carlsone on February 17, 2017, 08:02:44 AM

Title: Decreasing pH of a reaction at equilibrium
Post by: carlsone on February 17, 2017, 08:02:44 AM: Pb(s) + PbO₂(s) + 4H⁺(aq) + 2SO₄²^–(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.
Title: Re: Decreasing pH of a of a reaction at equilibrium
Post by: mjc123 on February 17, 2017, 08:21:30 AM: What happens when you have barium and sulfate ions in solution?
Title: Re: Decreasing pH of a reaction at equilibrium
Post by: carlsone on February 17, 2017, 09:07:45 AM: 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?
Title: Re: Decreasing pH of a reaction at equilibrium
Post by: mjc123 on February 17, 2017, 09:58:35 AM: Yes
Title: Re: Decreasing pH of a reaction at equilibrium
Post by: carlsone on February 17, 2017, 06:27:37 PM: 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.
Title: Re: Decreasing pH of a reaction at equilibrium
Post by: AWK on February 17, 2017, 07:18:49 PM: Think about electroneutrality of solution.
Title: Re: Decreasing pH of a reaction at equilibrium
Post by: carlsone on February 17, 2017, 07:28:11 PM: That's really helpful, thank you both. I was confining myself to acid/base and equilibrium concepts.