Join thousands of students who trust us to help them ace their exams!Watch the first video
Multiple Choice
Which of the following compounds would make for the best buffer at pH 8?
A
Acetic acid, pKa = 4.8
B
Tricine, pKa = 8.15
C
Glycine, pKa = 9.9
D
Tris, pKa = 8.3
Verified step by step guidance
1
Understand that a buffer is most effective when the pH is close to the pKa of the buffering agent. This is because the buffer can resist changes in pH when the concentrations of the acid and its conjugate base are equal, which occurs at the pKa.
Identify the pH at which the buffer needs to be effective. In this problem, the desired pH is 8.
Compare the pKa values of the given compounds to the desired pH. The closer the pKa is to the pH, the more effective the compound will be as a buffer at that pH.
Evaluate each compound: Acetic acid has a pKa of 4.8, which is far from 8, making it a poor buffer at pH 8. Glycine has a pKa of 9.9, which is also not close to 8. Tris has a pKa of 8.3, which is close to 8, and Tricine has a pKa of 8.15, which is even closer to 8.
Conclude that Tricine, with a pKa of 8.15, is the best choice for a buffer at pH 8, as its pKa is closest to the desired pH, allowing it to effectively resist changes in pH around this value.