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What pKa should be used to keep a buffer neutral?


lord farquaad:
The objective is to maintain pH = 7.0 for an enzyme-catalyzed reaction that will produce hydrogen ions along with the desired product. At equal concentrations, which weak acid, if any, will serve as the better buffer for the reaction:
acid A with pKa = 6.5, or acid B with pKa = 7.5?

a) acid A
b) acid B
c) water will work as good as either acid
d) both are equally effective

The answer is a) acid A.

I understand that when pKa is higher than pH, deprotonation occurs. Which makes choice a) the correct answer... I just feel like I'm missing something. I guess I'm not sure how adding the acid relates back to creating a buffer. I think I understand but want to be sure. We have a test coming up.

Think how produced H+ changes amounts of conjugate acid/base in the buffer in both cases.

For what ratio of conjugate acid/base is the buffer most effective?


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