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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: slayer on December 12, 2006, 11:49:47 PM

Title: Which buffer solution will have the the lowest pH?
Post by: slayer on December 12, 2006, 11:49:47 PM

NH₃ / NH₄Cl

PO₄^3- / HPO₄^2-

HSO₃^- / KOH

I initially assumed that HSO₃^- / KOH was the lowest pH because sulfuric acid is a very strong acid and KOH is a strong base, so they would both dissociate entirely.

is this a correct assumption?

Title: Re: Which buffer solution will have the the lowest pH?
Post by: Borek on December 13, 2006, 05:18:53 AM

Assumption is wrong, this is sulfurous acid, not sulfuric. And in a way you have posted the same question twice, shame on you. Finallly, you still haven't decided whether it is a buffer solution, or not.

Title: Re: Which buffer solution will have the the lowest pH?
Post by: slayer on December 13, 2006, 01:36:59 PM

Quote from: Borek on December 13, 2006, 05:18:53 AM

And in a way you have posted the same question twice, shame on you.

yea sorry about that borek. It was actually a two part problem where the first part I had to identify the above three as being buffers among a set of 6 combinations. I missed the HSO₃^- / KOH, so now I have to explain why it is a buffer system.

The second part of the problem was which of the buffer systems you selected has the lowest pH.  But if I was to establish which of the conjugates appeared to be more acidic, that would be the lowest pH, right?

Title: Re: Which buffer solution will have the the lowest pH?
Post by: AWK on December 14, 2006, 02:51:12 AM

Quote

HSO3- / KOH

This solution cannot exist.
KOH will react with HSO₃^- anion to form SO₃^2- anion, and both anions eventually form a buffer solution