Question

Question: Consider the titration of a generic weak acid HA with a strong base that gives the following titration curve:

On the curve indicate the points that correspond to the following.

a. The equivalence point

b. The maximum buffering region

c. $\mathbf{pH}\mathbf{=}{\mathbf{pK}}_{\mathbf{a}}$

d. pH depends only on [HA]

e. pH depends only on [A]

f. pH depends only on the amount of excess strong base added

Short answer

The equivalence point of the titration curve is point (a).

The maximum buffering region is shown as point (b).

At the half equivalence point, the pH is equal to the ${\text{pK}}_{\text{a}}$ . The point is shown as point (c).

Before the half equivalence point, the pH depends mainly on [HA]. The point is shown as (d).

After the half equivalence point, the pH depends mainly on $\left[{\mathrm{A}}^{-}\right]$; the point is shown as (e).

After the equivalence point with the addition of a strong base, the pH will increase abruptly. The point is shown as (f).

Step-by-step solution

Definition of titration curve

The plot of the pH of the analyte solution versus the volume of titrant added as the titration progresses is defined as the titration curve.

Explanations

The titration curve for the weak acid and strong base is represented as:

$$\begin{gathered} \mathbf{The}\mathbf{}\mathbf{point}\mathbf{}\mathbf{where}\mathbf{}\mathbf{the}\mathbf{}\mathbf{curve}\mathbf{}\mathbf{steepness}\mathbf{}\mathbf{is}\mathbf{}\mathbf{maximum}\mathbf{}\mathbf{is}\mathbf{}\mathbf{known}\mathbf{}\mathbf{as}\mathbf{}\mathbf{the}\mathbf{}\mathbf{equivalence} \\ \mathbf{}\mathbf{point}\mathbf{.} \end{gathered}$$

$\mathbf{The}\mathbf{}\mathbf{volume}\mathbf{}\mathbf{of}\mathbf{}\mathbf{the}\mathbf{}\mathbf{base}\mathbf{}\mathbf{is}\mathbf{}\mathbf{22}\mathbf{mL}\mathbf{}\mathbf{}\mathbf{which}\mathbf{}\mathbf{is}\mathbf{}\mathbf{shown}\mathbf{}\mathbf{as}\mathbf{}\mathbf{point}\mathbf{}\mathbf{a}\mathbf{.}$

Point (a) is the equivalence point.