A biochemist hat 100 mL of a 0.10 M solution of a buffer that contains a weak ac

Question

A biochemist hat 100 mL of a 0.10 M solution of a buffer that contains a weak acid with a pKa of 6.3. She adds 4 0 mL of 1 0 M HCl which changes the pH to 5 7 What was the pH of the original solution? Obstructive lung diseases prevent the efficient expiration of CO_2 how might this effect an individual's ability to regulate blood pH. Briefly explain showing the relevant equilibria. During the analysis of a small peptide you decide to inject the hydrolyzed peptide into an HPLC that has a cation exchange column. Your sample contains: Gly, Phe, Arg, Asn, and Asp What order would expect these AA to elute from the column? When you choose to use a pH gradient to elute your peptide, would you choose to start with high pH and move lower or vice versa, and why?

Explanation / Answer

Q7.

V = 100 mL

M = 0.1 buffer

pKa = 6.3

pH = pKa + log(A-/HA)

initially:

pH = 6.3 + log(A-/HA)

after addition:

5.7 = 6.3 + log(A-x/HA+x)

10^(5.7-6.3) = (A-x/HA+x)

mmol of HCL = MV = 4*1 = 4

so, x = 4

0.25118 = (A-x)/(HA+x)

0.25118 = (A-4)/(HA+4)

A+HA = MV = 100*0.1 = 10

so

0.25118 = (A-4)/(HA+4)

A = 10-HA

0.25118 = (10-HA-4)/(HA+4)

0.25118 HA + 4*0.25118 = 6 - HA

1.25118 HA = 6 - 4*0.25118

HA = (6 - 4*0.25118) / 1.25118= 3.9924

A = 10-HA = 10-3.9924= 6.0076

so

initially

pH = 6.3+log(6.0076/3.9924) = 6.47

Please consider posting multiple questions in multiple set of Q&A. According to Chegg's Q&A Guidelines, we are only allowed to answer to one questions per Q&A.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.