Chapter 20, Problem 45A

(a)

Interpretation Introduction

Interpretation: Whether the reaction, $Li\left(s\right)+H_{2}O\left(l\right)\to LiOH\left(aq\right)+H_2\left(g\right)$ is a redox reaction or not is to be determined.

Concept Introduction: The reaction which involves the reduction and oxidation process is the redox reaction. Oxidation involves the loss of electrons and reduction involves the gaining of electrons.

Answer to Problem 45A

The given reaction $Li\left(s\right)+H_{2}O\left(l\right)\to LiOH\left(aq\right)+H_2\left(g\right)$ is a redox reaction.

Explanation of Solution

In the given reaction,

  $Li\left(s\right)+H_{2}O\left(l\right)\to LiOH\left(aq\right)+H_2\left(g\right)$

Lithium, $Li$ increases its oxidation state from zero to +1 by the loss of electrons. So, it is an oxidation reaction.

Hydrogen, H in $H_{2}O$ changes its oxidation state from +1 to zero by the gaining of electrons.

So, it is a reduction reaction.

Since the given reaction involves both oxidation and reduction, it is a redox reaction.

(b)

Interpretation Introduction

Interpretation: Whether the reaction, $K_{2}C{r}_2{O}_7\left(aq\right)+HCl\left(aq\right)\to KCl\left(aq\right)+CrC{l}_3\left(aq\right)+H_{2}O\left(l\right)$ is a redox reaction or not is to be determined.

Concept Introduction: The reaction which involves the reduction and oxidation process is the redox reaction. Oxidation involves the loss of electrons and reduction involves the gaining of electrons.

Answer to Problem 45A

The given reaction $K_{2}C{r}_2{O}_7\left(aq\right)+HCl\left(aq\right)\to KCl\left(aq\right)+CrC{l}_3\left(aq\right)+H_{2}O\left(l\right)$ is a redox reaction.

Explanation of Solution

In the given reaction,

  $K_{2}C{r}_2{O}_7\left(aq\right)+HCl\left(aq\right)\to KCl\left(aq\right)+CrC{l}_3\left(aq\right)+H_{2}O\left(l\right)$

Chlorine, $Cl$ increases its oxidation state from -1 to 0 $\left(C{l}_2\right)$ by the loss of electrons. So it is an oxidation reaction.

Chromium, $Cr$ in $K_{2}C{r}_2{O}_7$ changes its oxidation state from +6 to +3 by the gaining of electrons. That is,

  $\left(\begin{array}{c}2x-14+2=0\\ x=+6\end{array}\right)$

So it is a reduction reaction.

Since the given reaction involves both oxidation and reduction, it is a redox reaction.

(c)

Interpretation Introduction

Interpretation: Whether the reaction, $Al\left(s\right)+HCl\left(aq\right)\to AlC{l}_3\left(aq\right)+H_2\left(g\right)$ is a redox reaction or not is to be determined.

Concept Introduction: The reaction which involves the reduction and oxidation process is the redox reaction. Oxidation involves the loss of electrons and reduction involves the gaining of electrons.

Answer to Problem 45A

The given reaction $Al\left(s\right)+HCl\left(aq\right)\to AlC{l}_3\left(aq\right)+H_2\left(g\right)$ is a redox reaction.

Explanation of Solution

In the given reaction,

  $Al\left(s\right)+HCl\left(aq\right)\to AlC{l}_3\left(aq\right)+H_2\left(g\right)$

Aluminum, Al increases its oxidation state from zero to +3 by the loss of electrons. So, it is an oxidation reaction.

Hydrogen, $H$ in $HCl$ changes its oxidation state from +1 to zero by gaining of electrons. So it is a reduction reaction.

Since the given reaction involves both oxidation and reduction, it is a redox reaction.

(d)

Interpretation Introduction

Interpretation: Whether the reaction, $C{l}_2\left(g\right)+H_{2}O\left(l\right)\to HCl\left(aq\right)+HClO\left(aq\right)$ is a redox reaction or not is to be determined.

Concept Introduction: The reaction which involves the reduction and oxidation process is the redox reaction. Oxidation involves the loss of electrons and reduction involves the gaining of electrons.

Answer to Problem 45A

The given reaction $C{l}_2\left(g\right)+H_{2}O\left(l\right)\to HCl\left(aq\right)+HClO\left(aq\right)$ is a redox reaction.

Explanation of Solution

In the given reaction,

  $C{l}_2\left(g\right)+H_{2}O\left(l\right)\to HCl\left(aq\right)+HClO\left(aq\right)$

Chlorine, $Cl$ increases its oxidation state from zero to +1 in $HClO$ by the loss of electrons. So, it is an oxidation reaction.

Chlorine, $Cl$ changes its oxidation state from zero to -1 by the gaining of electrons in $HCl$ . So, it is a reduction reaction.

Since the given reaction involves both oxidation and reduction, it is a redox reaction.

(e)

Interpretation Introduction

Interpretation: Whether the reaction, $I_2{O}_5\left(s\right)+CO\left(g\right)\to I_2\left(s\right)+4C{O}_2\left(g\right)$ is a redox reaction or not is to be determined.

Concept Introduction: The reaction which involves the reduction and oxidation process is the redox reaction. Oxidation involves the loss of electrons and reduction involves the gaining of electrons.

Answer to Problem 45A

The given reaction $I_2{O}_5\left(s\right)+CO\left(g\right)\to I_2\left(s\right)+4C{O}_2\left(g\right)$ is a redox reaction.

Explanation of Solution

In the given reaction,

  $I_2{O}_5\left(s\right)+CO\left(g\right)\to I_2\left(s\right)+4C{O}_2\left(g\right)$

Carbon, C in CO increases its oxidation state from +2 to +4 in $C{O}_2$ by the loss of electrons. So it is an oxidation reaction.

Iodine, I in $I_2{O}_5$ changes its oxidation state from +5 to zero by the gaining of electrons. So it is a reduction reaction.

Since the given reaction involves both oxidation and reduction, it is a redox reaction.

(f)

Interpretation Introduction

Interpretation: Whether the reaction, $H_{2}O\left(l\right)+S{O}_3\left(g\right)\to H_{2}S{O}_4\left(aq\right)$ is a redox reaction or not is to be determined.

Concept Introduction: The reaction which involves the reduction and oxidation process is the redox reaction. Oxidation involves the loss of electrons and reduction involves the gaining of electrons.

Answer to Problem 45A

The given reaction $H_{2}O\left(l\right)+S{O}_3\left(g\right)\to H_{2}S{O}_4\left(aq\right)$ is not a redox reaction.

Explanation of Solution

In the given reaction,

  $H_{2}O\left(l\right)+S{O}_3\left(g\right)\to H_{2}S{O}_4\left(aq\right)$

The oxidation number of sulphur, S in $S{O}_3$ and $H_{2}S{O}_4$ is +6. And that of hydrogen, H in $H_{2}O$ and $H_{2}S{O}_4$ is +1.

That means that there is no change in oxidation number in the reaction. So, it is not a redox reaction.