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I dont understand the answer to this acid and base question a level chem

Why couldn't it be A, I thought buffers could be alkali as wellScreenshot 2022-10-28 10.58.47 AM.pngScreenshot 2022-10-28 10.58.55 AM.png
(edited 1 year ago)
Original post by leoishush
Why couldn't it be A, I thought buffers could be alkali as wellScreenshot 2022-10-28 10.58.47 AM.pngScreenshot 2022-10-28 10.58.55 AM.png


The idea of a buffer is that it contains a high concentration of a weak acid and it's salt- so HA and A-. For a basic buffer requirement is for weak base and its salt - so NH3 and NH4+. In the case you suggest the solution would not consist of either of these as the hydroxide would lower the concentration of the acid.
Reply 2
ohhhhh its because sodium hydroxide is a strong base

Original post by Mole man
The idea of a buffer is that it contains a high concentration of a weak acid and it's salt- so HA and A-. For a basic buffer requirement is for weak base and its salt - so NH3 and NH4+. In the case you suggest the solution would not consist of either of these as the hydroxide would lower the concentration of the acid.
Original post by leoishush
ohhhhh its because sodium hydroxide is a strong base


No. It is because only in Z is the acid in excess (and some of the salt ion).

The other two mixtures either contain no acid, some salt and an excess of base OR a perfectly neutralised mixture containing salt only.
(edited 1 year ago)
Reply 4
Original post by Pigster
No. It is because only in Z is the acid in excess (and some of the salt ion).

The other two mixtures either contain no acid, some salt and an excess of base OR a perfectly neutralised mixture containing salt only.





but excess base could form alkali buffer?
Original post by leoishush
but excess base could form alkali buffer?


True, but alkaline buffers involve a weak base and its conjugate acid ion. NaOH is a strong base and hence can't form an alkaline buffer.

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