SEE EXAMPLE IN THE IMAGE A mixture of 0.20M acetic acid and 0.30M sodium acetate is given. Calculate the pH of the medium if the pKa of the acetic acid is 4.76. Show your complete solution.
SEE EXAMPLE IN THE IMAGE A mixture of 0.20M acetic acid and 0.30M sodium acetate is given. Calculate the pH of the medium if the pKa of the acetic acid is 4.76. Show your complete solution.
Chapter12: Water Requirements For Aquaculture
Section: Chapter Questions
Problem 27SA
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Question
SEE EXAMPLE IN THE IMAGE
A mixture of 0.20M acetic acid and 0.30M sodium acetate is given. Calculate the pH of the medium if the pKa of the acetic acid is 4.76. Show your complete solution.
![Sample Problems
1. The pH of the given solution of lactic acid and lactate is 4.30. Calculate the pka
of lactic acid, when the concentration of lactic acid and lactate are 0.020M and
0.073M, respectively.
Solution:
A.) Following components are given in the equation:
pH of the medium = 4.30
Concentration of lactate ion (proton acceptor) = 0.073M
Concentration of lactic acid (proton donor) = 0.020M
B.) Formula:
[Proton Acceptor]
[Proton Donor]
pH
pKa + log
%3D
We need to calculate the pKa of lactic acid. So, take out the pKa to the left side and
the equation now becomes:
[Proton Acceptor]
log
[Proton Donor]
pKa
pH
%3D
C.) Substitute the given values in the new equation:
0.073
pKa =
4.30 – log
0.020
4.30 – log 3.65
log 3.65 is 0.56
pKa =
4.30 – 0.56
3.74
Answer: the pKa of the given solution is 3.74
C.) Substitute the given values in the new equation:
0.073
pKa
4.30 – log
%3D
0.020
4.30 – log 3.65
%3D
log 3.65 is 0.56
pKa =
4.30 – 0.56
3.74
%3D
Answer: the pKa of the given solution is 3.74](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1ac265d4-e05b-453a-8fb0-a7cea587ddec%2Fa318a46a-cb1a-46cb-b4b6-4808054cd9e0%2F8drqqjq_processed.jpeg&w=3840&q=75)
Transcribed Image Text:Sample Problems
1. The pH of the given solution of lactic acid and lactate is 4.30. Calculate the pka
of lactic acid, when the concentration of lactic acid and lactate are 0.020M and
0.073M, respectively.
Solution:
A.) Following components are given in the equation:
pH of the medium = 4.30
Concentration of lactate ion (proton acceptor) = 0.073M
Concentration of lactic acid (proton donor) = 0.020M
B.) Formula:
[Proton Acceptor]
[Proton Donor]
pH
pKa + log
%3D
We need to calculate the pKa of lactic acid. So, take out the pKa to the left side and
the equation now becomes:
[Proton Acceptor]
log
[Proton Donor]
pKa
pH
%3D
C.) Substitute the given values in the new equation:
0.073
pKa =
4.30 – log
0.020
4.30 – log 3.65
log 3.65 is 0.56
pKa =
4.30 – 0.56
3.74
Answer: the pKa of the given solution is 3.74
C.) Substitute the given values in the new equation:
0.073
pKa
4.30 – log
%3D
0.020
4.30 – log 3.65
%3D
log 3.65 is 0.56
pKa =
4.30 – 0.56
3.74
%3D
Answer: the pKa of the given solution is 3.74
![2. What is the ratio of the concentration of acetic acid and acetate ions required
to prepare a buffer with pH 5.20. The pka of acetic acid is 4.76.
Solution:
You cannot directly apply the Henderson - Hasselbalch equation because it is an
indirect question. First, you need to rearrange the equation accordingly.
A.) Following components are given in the equation:
pH of the buffer = 5.20
pka of acetic acid = 4.76
B.) Formula:
[Proton Acceptor]
pH = pka + log
[Proton Donor]
C.) Rearrange the Components:
[Proton Acceptor]
log
[Proton Donor]
= pH - pKa
[Proton Acceptor]
log
[Proton Donor]
= 5.20 – 4.76
[Proton Acceptor]
log
[Proton Donor]
= 0.44
[Proton Acceptor]
log
= antilog of 0.44 = 2.75
[Proton Donor]
Answer: The ratio of acetate to acetic acid required to get pH of 5.20 is 2.75.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1ac265d4-e05b-453a-8fb0-a7cea587ddec%2Fa318a46a-cb1a-46cb-b4b6-4808054cd9e0%2Fez4etq_processed.jpeg&w=3840&q=75)
Transcribed Image Text:2. What is the ratio of the concentration of acetic acid and acetate ions required
to prepare a buffer with pH 5.20. The pka of acetic acid is 4.76.
Solution:
You cannot directly apply the Henderson - Hasselbalch equation because it is an
indirect question. First, you need to rearrange the equation accordingly.
A.) Following components are given in the equation:
pH of the buffer = 5.20
pka of acetic acid = 4.76
B.) Formula:
[Proton Acceptor]
pH = pka + log
[Proton Donor]
C.) Rearrange the Components:
[Proton Acceptor]
log
[Proton Donor]
= pH - pKa
[Proton Acceptor]
log
[Proton Donor]
= 5.20 – 4.76
[Proton Acceptor]
log
[Proton Donor]
= 0.44
[Proton Acceptor]
log
= antilog of 0.44 = 2.75
[Proton Donor]
Answer: The ratio of acetate to acetic acid required to get pH of 5.20 is 2.75.
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