Chapter 11, Problem 11.16P

(a)

Interpretation Introduction

Interpretation:

Value of $\text{pH}$ when $\left[{\text{H}}_{\text{2}}\text{A}\right]$ equals to $\left[{\text{HA}}^{-}\right]$ has to be calculated.

Concept Introduction:

The equation for buffer is described by Henderson-Hasselbach equation and it is a rearranged for of equilibrium constant, $K_{\text{a}}$. Consider an equation of dissociation of an acid as follows:

  $\text{HA}\rightleftharpoons {\text{H}}^{+}+{\text{A}}^{-}$

Formula to calculate $\text{pH}$ is as follows:

  $\text{pH}=\text{p}{K}_{\text{a}}+\log \left(\frac{\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}\right)$

Here,

$\text{p}{K}_{\text{a}}$ is acid dissociation constant of weak acid $\text{HA}$.

$\left[{\text{A}}^{-}\right]$ is concentration of conjugate base ${\text{A}}^{-}$

$\left[\text{HA}\right]$ is concentration of acid $\text{HA}$.

(b)

Interpretation Introduction

Interpretation:

Value of $\text{pH}$ when $\left[{\text{A}}^{2-}\right]$ equals to $\left[{\text{HA}}^{-}\right]$ has to be calculated.

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

Interpretation:

Among ${\text{H}}_2\text{A}$, ${\text{HA}}^{-}$ or ${\text{A}}^{2-}$ principal species at $\text{pH}$ equals to 2 has to be determined.

Concept Introduction:

Refer to part (a).

(d)

Interpretation Introduction

Interpretation:

Among ${\text{H}}_2\text{A}$, ${\text{HA}}^{-}$ or ${\text{A}}^{2-}$ principal species at $\text{pH}$ equals to 6 has to be determined.

Concept Introduction:

Refer to part (a).

(e)

Interpretation Introduction

Interpretation:

Among ${\text{H}}_2\text{A}$, ${\text{HA}}^{-}$ or ${\text{A}}^{2-}$ principal species at $\text{pH}$ equals to 10 has to be determined.

Concept Introduction:

Refer to part (a).