Question

An analytical chemist is titrating 245.7 mL of 0.7500 M solution of propionic acid (HC₂H₅CO₂) with a 0.8200 M solution of KOH. The pKa of propionic acid is 4.89. Calculate the pH of the acid solution after the chemist has added 106.2 mL of the KOH solution to it.

A) 3.21
B) 4.89
C) 7.00
D) 8.45

Answer 1

To determine the pH of the acid solution after adding KOH, use the Henderson-Hasselbalch equation to calculate the concentration of the acetate ion.

Step-by-step explanation:

The pH of the acid solution can be determined using the Henderson-Hasselbalch equation. 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. In this case, the initial concentration of propionic acid is 0.7500 M, and the concentration of the conjugate base (acetate ion) is determined by the amount of KOH solution added. To calculate the pH after adding 106.2 mL of the KOH solution, we need to determine the moles of KOH added and then calculate the concentration of the resulting acetate ion.