help please! The quiz question is as follows: You are planning to carry out a re

Question

help please!

The quiz question is as follows:

You are planning to carry out a reaction at pH =4 that releases protons. Would it be better to use a 1.0 M formic acid/sodium buffer or a 1.0 M acetic acid/sodium acetate buffer? (pKa formic acid 3.75; pKa acetic acid 4.76.)

The answer to the question is formic acid/sodium buffer.

My question: why is the formic acid/sodium buffer the preffered buffer for this reaction? My thinking is that if the reaction is releasing protons, this would raise the acidity of the reaction overall. It would seem to me that a buffer with the more basic pKa (meaning a pKa above the pH of 4) would keep the reaction optimally buffered. Obviously there is a flaw somewhere in my logic or I am not understanding the subject material correctly. My textbook offers no explaination to assist me with this. Please help me to understand this concept better. If anyone can offer a step by step solution it would be greatly appreciated.

Thank you!!

Explanation / Answer

pKa of formic acid 3.75 is nearer to desired pH 4.0. so formic/sodium formate is better buffer.

If pKa is closer to pH then buffer works effectively. Buffer works more effective at pH = pKa.

Buffer shows its capacity in the pH range of pKa+1 to pKa-1.

So acetic acid/sodium acetate buffer can also use to get pH 4.0. but formic acid/Sodium formate is better than acetate buffer.

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