tion at pH 9 has a ratio of [HA]/[A-] of 10. What is the pKa of the acid? solution of 0.03 M NaOH is:
tion at pH 9 has a ratio of [HA]/[A-] of 10. What is the pKa of the acid? solution of 0.03 M NaOH is:
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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![**Buffer and pH Calculations**
---
**Question 3:**
A buffer solution at pH 9 has a ratio of \([HA]/[A^-]\) of 10. What is the \(pK_a\) of the acid?
A. 7
B. 8
C. 9
D. 10
E. 11
---
**Question 4:**
The pH of a solution of 0.03 M NaOH is:
A. 0.003
B. 1.53
C. 3.00
D. 7.00
E. 9.53
F. 12.47
G. The pH cannot be determined
---
In Question 3, you are required to understand the relationship between the pH of a solution, the ratio of the concentration of the acid (\([HA]\)) to its conjugate base (\([A^-]\)), and the \(pK_a\) of the acid. This relationship is given by the Henderson-Hasselbalch equation:
\[ pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right) \]
The buffer solution has a pH of 9, and the ratio \([HA]/[A^-] = 10\), which implies \(\left( \frac{[A^-]}{[HA]} \right) = \frac{1}{10} \). Plugging these values into the equation:
\[ 9 = pK_a + \log \left( \frac{1}{10} \right) \]
\[ 9 = pK_a - 1 \]
\[ pK_a = 10 \]
Thus, the correct answer is D. 10
For Question 4, you need to calculate the pH of a solution of 0.03 M NaOH, a strong base that fully dissociates in water:
\[ NaOH \rightarrow Na^+ + OH^- \]
Since the concentration of \( OH^- \) is 0.03 M, one can calculate the pOH of the solution and then use it to find the pH:
\[ pOH = -\log [OH^-] \]
\[ pOH = -\log (0.03) \approx 1.53 \]
\[ pH = 14 - pOH \](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F98bfadad-2e46-40d9-a2de-6f1567de7085%2F7627fccd-b62b-458d-a8ca-841d27ddb6c5%2Fpcp4r1le_processed.png&w=3840&q=75)
Transcribed Image Text:**Buffer and pH Calculations**
---
**Question 3:**
A buffer solution at pH 9 has a ratio of \([HA]/[A^-]\) of 10. What is the \(pK_a\) of the acid?
A. 7
B. 8
C. 9
D. 10
E. 11
---
**Question 4:**
The pH of a solution of 0.03 M NaOH is:
A. 0.003
B. 1.53
C. 3.00
D. 7.00
E. 9.53
F. 12.47
G. The pH cannot be determined
---
In Question 3, you are required to understand the relationship between the pH of a solution, the ratio of the concentration of the acid (\([HA]\)) to its conjugate base (\([A^-]\)), and the \(pK_a\) of the acid. This relationship is given by the Henderson-Hasselbalch equation:
\[ pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right) \]
The buffer solution has a pH of 9, and the ratio \([HA]/[A^-] = 10\), which implies \(\left( \frac{[A^-]}{[HA]} \right) = \frac{1}{10} \). Plugging these values into the equation:
\[ 9 = pK_a + \log \left( \frac{1}{10} \right) \]
\[ 9 = pK_a - 1 \]
\[ pK_a = 10 \]
Thus, the correct answer is D. 10
For Question 4, you need to calculate the pH of a solution of 0.03 M NaOH, a strong base that fully dissociates in water:
\[ NaOH \rightarrow Na^+ + OH^- \]
Since the concentration of \( OH^- \) is 0.03 M, one can calculate the pOH of the solution and then use it to find the pH:
\[ pOH = -\log [OH^-] \]
\[ pOH = -\log (0.03) \approx 1.53 \]
\[ pH = 14 - pOH \
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