Work 2: Measuring pK1 for glycine K1 of an ampholite can be calculated by measuring the pH of a solution with well-known ampholite (CA) and acid (cacid) concentrations. • Use 25 cm3 beakers to prepare the following three solutions: Table 1 Serial Number: #1 #2 #3 0.2 M glycine solution, cm³ 5 0.01 M HCI solution, cm³ 10 15 15 10 5 pH obtained 4.22 4.39 4.50 • Calibrate the electrode with a pH = 4.00 buffer (knob buffer 1). Measure the pH of each solution then calculate [H3O+], ÇA, cacid and finally K1 using equation (5). Average the three values.
Work 2: Measuring pK1 for glycine K1 of an ampholite can be calculated by measuring the pH of a solution with well-known ampholite (CA) and acid (cacid) concentrations. • Use 25 cm3 beakers to prepare the following three solutions: Table 1 Serial Number: #1 #2 #3 0.2 M glycine solution, cm³ 5 0.01 M HCI solution, cm³ 10 15 15 10 5 pH obtained 4.22 4.39 4.50 • Calibrate the electrode with a pH = 4.00 buffer (knob buffer 1). Measure the pH of each solution then calculate [H3O+], ÇA, cacid and finally K1 using equation (5). Average the three values.
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![Work 2: Measuring pK1 for glycine
K1 of an ampholite can be calculated by measuring the pH of a solution with well-known ampholite (CA)
and acid (cacid) concentrations.
• Use 25 cm3 beakers to prepare the following three solutions:
Table 1
Serial Number:
#1
#2
#3
0.2 M glycine solution, cm³ 5
0.01 M HCI solution, cm³
10
15
15
10
5
pH obtained
4.22
4.39
4.50
• Calibrate the electrode with a pH = 4.00 buffer (knob buffer 1). Measure the pH of each solution then
calculate [H3O+], ÇA cacid and finally K1 using equation (5).
• Average the three values.
Process (1) happens in acidic solutions, where deprotonation of A-is neglicted. Ki can be
calculated based on a titration of glycine with a strong acid. In the following derivation,
the total concentration of glycine is indicated as ca, the concentration of the acid (titrant)
is Cacid. In this case:
CA = [A*]+ [A*]
[H;O"] + [A*]
(3)
Cacid
%3D
(4)
By combining equations (1) (3) and (4):
[H,O*](ca - c,cid +[H;O*])
Cacid - [H,O*]
K,
(5)
Based on this formula, Kı can be calculated by measuting the pH of a glycine solution
with well-known ca and cacid.
For the second deprotonation process of glycine:](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F8d870417-90fa-4e90-962a-13f10d87b3a0%2F01b84bd1-46fa-4204-9df8-663ed40b949d%2Fw73mb5b_processed.png&w=3840&q=75)
Transcribed Image Text:Work 2: Measuring pK1 for glycine
K1 of an ampholite can be calculated by measuring the pH of a solution with well-known ampholite (CA)
and acid (cacid) concentrations.
• Use 25 cm3 beakers to prepare the following three solutions:
Table 1
Serial Number:
#1
#2
#3
0.2 M glycine solution, cm³ 5
0.01 M HCI solution, cm³
10
15
15
10
5
pH obtained
4.22
4.39
4.50
• Calibrate the electrode with a pH = 4.00 buffer (knob buffer 1). Measure the pH of each solution then
calculate [H3O+], ÇA cacid and finally K1 using equation (5).
• Average the three values.
Process (1) happens in acidic solutions, where deprotonation of A-is neglicted. Ki can be
calculated based on a titration of glycine with a strong acid. In the following derivation,
the total concentration of glycine is indicated as ca, the concentration of the acid (titrant)
is Cacid. In this case:
CA = [A*]+ [A*]
[H;O"] + [A*]
(3)
Cacid
%3D
(4)
By combining equations (1) (3) and (4):
[H,O*](ca - c,cid +[H;O*])
Cacid - [H,O*]
K,
(5)
Based on this formula, Kı can be calculated by measuting the pH of a glycine solution
with well-known ca and cacid.
For the second deprotonation process of glycine:
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