Question

What is the ratio of acetic acid (pK = 4.76) to acetate(-) in a 2.0 M acetate solution with a pH = 6.76?

a) 1:1
b) 10:1
c) 100:1
d) 1000:1

Answer 1

Using the Henderson-Hasselbalch equation, the ratio of acetate to acetic acid in the solution with a pH of 6.76 and pKa of 4.76 is found to be 100:1.

Step-by-step explanation:

The question asks to find the ratio of acetic acid to acetate in a solution with a given pH and known pKa. We can use the Henderson-Hasselbalch equation to solve this:

For a weak acid and its conjugate base, the equation is: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid.

Here, pH = 6.76 and pKa = 4.76. Plugging these values into the equation and solving for the ratio [A-]/[HA] gives us:

6.76 = 4.76 + log([A-]/[HA])
log([A-]/[HA]) = 6.76 - 4.76
log([A-]/[HA]) = 2
Converting from logarithmic form:
[A-]/[HA] = 10²
Therefore, the ratio of acetate to acetic acid is 100:1, which corresponds to option (c).