Chapter 14, Problem 108QP

(a)

Interpretation Introduction

Interpretation:

Whether the statement, “The water is present at the side of the equilibrium and has a coefficient of $6$ � is correct or not is to be identified.

Explanation of Solution

The ionic skeleton chemical equation for the given reaction is shown in equation (1).

${\text{I}}_2\left(s\right)+{\text{NO}}_3^{-}\left(aq\right)\stackrel{}{\to }{\text{HIO}}_3+{\text{NO}}_2\left(g\right)\mathrm{......}\left(1\right)$

The oxidation numbers of all the atoms in equation (1) that undergo a redox reaction have been assigned and shown in equation (2).

${\stackrel{0}{\text{I}}}_2\left(s\right)+\stackrel{+5}{\text{N}}{\text{O}}_3^{-}\left(aq\right)\stackrel{}{\to }\text{H}\stackrel{+5}{\text{I}}{\text{O}}_3+\stackrel{+4}{\text{N}}{\text{O}}_2\left(g\right)\mathrm{......}\left(2\right)$

To balance the iodine atom on both sides of equation (2), $2$ is used as a coefficient for ${\text{HIO}}_3$ .

${\stackrel{0}{\text{I}}}_2\left(s\right)+\stackrel{+5}{\text{N}}{\text{O}}_3^{-}\left(aq\right)\stackrel{}{\to }2\text{H}\stackrel{+5}{\text{I}}{\text{O}}_3^{-}+\stackrel{+5}{\text{N}}{\text{O}}_2\left(g\right)\mathrm{......}\left(3\right)$

Equation (4) represents the oxidation half-reaction and equation (5) represents the reduction half-reaction.

$\begin{array}{l}{\stackrel{0}{\text{I}}}_2\left(s\right)\stackrel{}{\to }2\text{H}\stackrel{+5}{\text{I}}{\text{O}}_3^{-}\left(aq\right)+10e^{-}\mathrm{......}\left(4\right)\\ \stackrel{+5}{\text{N}}{\text{O}}_3^{-}\left(aq\right)+e^{-}\stackrel{}{\to }\stackrel{+4}{\text{N}}{\text{O}}_2\left(g\right)\mathrm{......}\left(5\right)\end{array}$

In equation (6), equation (5) is multiple by $10$ and added to equation (4).

$\begin{array}{l}\underset{¯}{\begin{array}{l}{\stackrel{0}{\text{I}}}_2\left(s\right)\stackrel{}{\to }2\text{H}\stackrel{+5}{\text{I}}{\text{O}}_3^{-}\left(aq\right)+10e^{-}\mathrm{......}\left(4\right)\\ \stackrel{+5}{\text{10N}}{\text{O}}_3^{-}\left(aq\right)+10e^{-}\stackrel{}{\to }10\stackrel{+4}{\text{N}}{\text{O}}_2\left(g\right)\mathrm{......}\left(6\right)\end{array}}\\ {\stackrel{0}{\text{I}}}_2\left(s\right)+\stackrel{+5}{\text{10N}}{\text{O}}_3^{-}\left(aq\right)\stackrel{}{\to }2\stackrel{+5}{\text{I}}{\text{O}}_3^{-}\left(aq\right)+10\stackrel{+4}{\text{N}}{\text{O}}_2\left(g\right)\mathrm{......}\left(7\right)\end{array}$

To balance the negative charges on both sides, $10$ ${\text{H}}^{+}$ ions are added to the left side of equation (7).

${\stackrel{0}{\text{I}}}_2\left(s\right)+\stackrel{+5}{\text{10N}}{\text{O}}_3^{-}\left(aq\right)+10{\text{H}}^{+}\left(aq\right)\stackrel{}{\to }2\text{H}\stackrel{+5}{\text{I}}{\text{O}}_3^{-}\left(aq\right)+10\stackrel{+4}{\text{N}}{\text{O}}_2\left(g\right)\mathrm{......}\left(8\right)$

To balance the ${\text{H}}^{+}$ ions on both sides, $4$ water molecules are added to the right side of the equation (8).

${\stackrel{0}{\text{I}}}_2\left(s\right)+\stackrel{+5}{\text{10N}}{\text{O}}_3^{-}\left(aq\right)+10{\text{H}}^{+}\left(aq\right)\stackrel{}{\to }2\text{H}\stackrel{+5}{\text{I}}{\text{O}}_3^{-}\left(aq\right)+10\stackrel{+4}{\text{N}}{\text{O}}_2\left(g\right)+4{\text{H}}_2\text{O}\left(l\right)\mathrm{......}\left(9\right)$

According to equation (9), ${\text{H}}_2\text{O}\left(l\right)$ is on the right side of the reaction and has a coefficient of $4$ . The coefficient of ${\text{NO}}_2\left(g\right)$ is $10$ , the number of ${\text{H}}^{+}$ ion on the left side of the reaction is $10$ , the coefficient of ${\text{NO}}_3^{-}$ is $10$ , and a total of $10e^{-}$ are transferred in the given reaction.

Option (A) is incorrect because according to equation (9), ${\text{H}}_2\text{O}\left(l\right)$ is on the right side of the reaction and has a coefficient of $4$ .

(b)

Interpretation Introduction

Interpretation:

Whether the statement, “The coefficient of ${\text{NO}}_2\left(g\right)$ is $5$ � is correct or not is to be identified.

Explanation of Solution

Option (B) is incorrect because according to equation (9), the coefficient of ${\text{NO}}_2\left(g\right)$ is $10$ .

(c)

Interpretation Introduction

Interpretation:

Whether the statement, “ ${\text{H}}^{+}\left(aq\right)$ is present at the side of the equilibrium and has a coefficient of $10$ � is correct or not is to be identified.

Explanation of Solution

Option (C) is correct because according to equation (9), the coefficient of ${\text{H}}^{+}\left(aq\right)$ is $10$ .

(d)

Interpretation Introduction

Interpretation:

Whether the statement, “The coefficient of ${\text{NO}}_3^{-}\left(aq\right)$ is $5$ � is correct or not is to be identified.

Explanation of Solution

Option (D) is incorrect because according to equation (9), the coefficient of ${\text{NO}}_3^{-}\left(aq\right)$ is $10$ .

(e)

Interpretation Introduction

Interpretation:

Whether the statement, “Five electrons are transferred in the reaction for every molecule of ${\text{I}}_2$ � is correct or not is to be identified.

Explanation of Solution

Option (E) is incorrect because a total of $10e^{-}$ are transferred for every ${\text{I}}_2$ molecule in the given reaction.