Question

In: Chemistry

You wish to make a buffer with a pH of 11. A) Which of the following...

You wish to make a buffer with a pH of 11.

A) Which of the following amino acids would you use to make your buffer: glutamine, aspartate, histidine, or tyrosine?

B) Why would your chosen amino acid be better than the others?

C) Start with 0.02M of the base form of your amino acid and calculate the concentration of the acidic form needed to have your buffer at the desire pH of 11. Show your work.

This is the third time I have posted this question. I believe the answer to A is histidine. I believe the answer to B is because histidine is basic. I really need the explanation for part C. However, please confirm that my answers for A and B are correct.

Solutions

Expert Solution

In strongly basic solutions (pH > 9), the predominant form is the fully deprotonated aminocarboxylate anion. This species would have a net charge of -1.

In common chemical usage, a pH buffer is a substance or a mixture of substances, that permits solutions to resist large changes in the pH upon addition of small amounts of H+

andOH-ions.

All the amino acids possess a single α-amino group and a single α-carboxyl group and R-group

So in amino acids, α-carboxyl group acts as conjugate acid (proton donor) and α-amino groupacts as proton acceptor. Together α-carboxyl group and α-amino group resists change in pH by partially absorbing additions of H+

or OH-ions to the system.

B)

AS Histidine is the basic amino acid with pka value of 9.17 so

A).

so Histidine  is ther best option.

Many other amino acid acts as buffer at different pH depending on their isoelectric pH and pka values.

C) answer is 0.016 M concentration of acid should be added for a change of PH =+1 or -1,

When we have a buffer we can use the Hendersen-Hasselbach equation. This is nice since it is the simplest treatment of the acid-base equilibrium.

using all and pka=ph for buffer we get,

c)

queen_honey_blossom answered 2 years ago
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