Chapter 9, Problem 9.34EP

(a)

Interpretation Introduction

Interpretation

For the given pairs - reducing agent and gain of electrons, whether the concepts of pairing are correct or not have to be indicated.

Concept Introduction:

Reducing agent:

The substance which is getting oxidized in redox reaction is the reducing agent.  It will lose electrons in the reaction.  Formic acid, earth metals, sulfites are examples of reducing agent.

Example:

Consider the reaction:

    ${\text{N}}_{\text{2}}{\text{+3H}}_{\text{2}}\underset{}{\to }{\text{2NH}}_{\text{3}}$

Oxidation No of ${\text{N}}_{\text{2}}=0$

Oxidation No of ${\text{H}}_{\text{2}}\text{= 0}$

Oxidation No of Nitrogen in ${\text{NH}}_{\text{3}}\text{= -3}$

Oxidation No of Hydrogen in ${\text{NH}}_{\text{3}}\text{= +1}$

${\text{N}}_{\text{2}}$ loses electrons and ${\text{H}}_{\text{2}}$ gains electrons in this redox reaction.

Hence ${\text{H}}_{\text{2}}$ is the reducing agent.

(b)

Interpretation Introduction

Interpretation:

For the given pairs – substance oxidized and increases in oxidation number, whether the concepts of pairing are correct or not has to be indicated.

Concept Introduction:

Oxidation:

Loss of electrons from an atom ion or molecule during a chemical reaction is known as oxidation.  Oxidation state of atom ion or molecule will increase in this process.  In simple it is the addition of oxygen.  Reduction is gaining of electrons.

Example    

Here ${\text{Fe}}^{\text{2+}}$ oxidized to ${\text{Fe}}^{\text{3+}}$ by the removal of a single electron.

Oxidizing agent:

Oxidizing agent will gain electrons but itself will get reduced in the reaction.  Oxygen, Hydrogen peroxide are good oxidizing agent.

Example:

Consider the reaction:

    ${\text{N}}_{\text{2}}{\text{+3H}}_{\text{2}}\underset{}{\to }{\text{2NH}}_{\text{3}}$

Oxidation No of ${\text{N}}_{\text{2}}=0$

Oxidation No of ${\text{H}}_{\text{2}}\text{= 0}$

Oxidation No of Nitrogen in ${\text{NH}}_{\text{3}}\text{= -3}$

Oxidation No of Hydrogen in ${\text{NH}}_{\text{3}}\text{= +1}$

${\text{N}}_{\text{2}}$ Loses electrons and ${\text{H}}_{\text{2}}$ gains electrons in this redox reaction.  Hence ${\text{N}}_{\text{2}}$ is the oxidizing agent.

(c)

Interpretation Introduction

Interpretation

For the given pairs – oxidizing agent and gain of electrons, whether the concepts of pairing are correct or not have to be indicated.

Concept Introduction:

Oxidation:

Loss of electrons from an atom ion or molecule during a chemical reaction is known as oxidation.  Oxidation state of atom ion or molecule will increase in this process.  In simple it is the addition of oxygen.  Reduction is gaining of electrons.

Example    

Here ${\text{Fe}}^{\text{2+}}$ oxidized to ${\text{Fe}}^{\text{3+}}$ by the removal of a single electron.

Oxidizing agent:

Oxidizing agent will gain electrons but itself will get reduced in the reaction.  Oxygen, Hydrogen peroxide are good oxidizing agent.

Example:

Consider the reaction:

    ${\text{N}}_{\text{2}}{\text{+3H}}_{\text{2}}\underset{}{\to }{\text{2NH}}_{\text{3}}$

Oxidation No of ${\text{N}}_{\text{2}}=0$

Oxidation No of ${\text{H}}_{\text{2}}\text{= 0}$

Oxidation No of Nitrogen in ${\text{NH}}_{\text{3}}\text{= -3}$

Oxidation No of Hydrogen in ${\text{NH}}_{\text{3}}\text{= +1}$

${\text{N}}_{\text{2}}$ Loses electrons and ${\text{H}}_{\text{2}}$ gains electrons in this redox reaction.  Hence ${\text{N}}_{\text{2}}$ is the oxidizing agent.

(d)

Interpretation Introduction

Interpretation:

For the given pairs – reducing agent and substance reduced, whether the concepts of pairing are correct or not has to be indicated.

Concept Introduction:

Oxidation:

Loss of electrons from an atom ion or molecule during a chemical reaction is known as oxidation.  Oxidation state of atom ion or molecule will increase in this process.  In simple it is the addition of oxygen.  Reduction is gaining of electrons.

Example    

Here ${\text{Fe}}^{\text{2+}}$ oxidized to ${\text{Fe}}^{\text{3+}}$ by the removal of a single electron.

Reducing agent:

The substance which is getting oxidized in redox reaction is the reducing agent.  It will lose electrons in the reaction.  Formic acid, earth metals, sulfites are examples of reducing agent.

Example:

Consider the reaction:

    ${\text{N}}_{\text{2}}{\text{+3H}}_{\text{2}}\underset{}{\to }{\text{2NH}}_{\text{3}}$

Oxidation No of ${\text{N}}_{\text{2}}=0$

Oxidation No of ${\text{H}}_{\text{2}}\text{= 0}$

Oxidation No of Nitrogen in ${\text{NH}}_{\text{3}}\text{= -3}$

Oxidation No of Hydrogen in ${\text{NH}}_{\text{3}}\text{= +1}$

${\text{N}}_{\text{2}}$ Loses electrons and ${\text{H}}_{\text{2}}$ gains electrons in this redox reaction.

Hence ${\text{H}}_{\text{2}}$ is the reducing agent.