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Buffer pH

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Could some explain in depth why the answer is C and not the other 3?
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Borek
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What do you need for a buffer solution?

And what pKa do you need for a buffer with pH over 7?
Original post by Borek
What do you need for a buffer solution?

And what pKa do you need for a buffer with pH over 7?


For an acidic buffer solution you need a weak acid and its salt and for an alkaline buffer solution you need a weak base and its salt

I don't know the answer for the second question. I know that pH=pkA + log(salt/weak acid) only
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Borek
4
Original post by scientific222
For an acidic buffer solution you need a weak acid and its salt and for an alkaline buffer solution you need a weak base and its salt


That's not 100% correct. It is not about having an acid and its salt, it is about having acid and its conjugate base.

I don't know the answer for the second question. I know that pH=pkA + log(salt/weak acid) only


pH has to be close to pKa. For a reasonably effective buffer you want pH to be between pKa-1 and pKa+1.

Try to apply these to all answers.

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