Chapter 11, Problem 11.18P

(a)

Interpretation Introduction

Interpretation:

Value of $\text{p}{K}_{\text{a}}$ for acid ${\text{BH}}^{+}$ has to be calculated.

Concept Introduction:

Ionic product of water is denoted by $K_{\text{w}}$ and is expressed as follows:

  $K_{\text{w}}=K_{\text{a}}{K}_{\text{b}}$

Here,

$K_{\text{a}}$ is acid equilibrium constant.

$K_{\text{b}}$ is base equilibrium constant.

(b)

Interpretation Introduction

Interpretation:

Value of $\text{pH}$ at $\left[{\text{BH}}^{+}\right]$ equals to $\left[\text{B}\right]$ 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:

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

Here,

$p{K}_{\text{a}}$ 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 $\text{HA}$.

(c)

Interpretation Introduction

Interpretation:

Among ${\text{BH}}^{+}$ or $\text{B}$ principal species at $\text{pH}$ equals to 7 has to be determined.

Concept Introduction:

Refer to part (b).

(d)

Interpretation Introduction

Interpretation:

Value of $\frac{\left[\text{B}\right]}{\left[{\text{BH}}^{+}\right]}$ at $\text{pH}$ 12 has to be determined.

Concept Introduction:

Refer to part (b).