Question

Of the following solutions, which has the greatest buffering capacity?

a. 0.365M HC2H3O2 and 0.497 M NaC2H3O2
b. 0.521 M HC2H3O2 and 0.217 M NaC2H3O2
c. 0.821 M HC2H3O2 and 0.713 M NaC2H3O2
d. 0.121 M HC2H3O2 and 0.116 M NaC2H3O2

Answer 1

Answer:

d. 0.121 M HC2H3O2 and 0.116 M NaC2H3O2

Explanation:

Hello,

In this case, since the pH variation is analyzed via the Henderson-Hasselbach equation:

$pH=pKa+log(\frac{[Base]}{[Acid]} )$

We can infer that the nearer to 1 the ratio of of the concentration of the base to the concentration of the acid the better the buffering capacity. In such a way, since the sodium acetate is acting as the base and the acetic acid as the acid, we have:

a. $\frac{[Base]}{[Acid]}=\frac{0.497M}{0.365M}=1.36$

b. $\frac{[Base]}{[Acid]}=\frac{0.217M}{0.521M}=0.417$

c. $\frac{[Base]}{[Acid]}=\frac{0.713M}{0.821M}=0.868$

d. $\frac{[Base]}{[Acid]}=\frac{0.116M}{0.121M}=0.959$

Therefore, the d. solution has the best buffering capacity.

Regards.