Chapter 18, Problem 100AP

Interpretation Introduction

(a)

Interpretation:

The given half reaction should be balanced

Concept Introduction:

The oxidation-reduction reaction is also known as a redox reaction. In this reaction, one reactant is oxidized and other is reduced. In balancing an oxidation-reduction reaction, they must be first divided into two half reactions: one is oxidation reaction and other is reduction reaction.

The balancing of redox reaction is complicated as compared to simple balancing. It is necessary to determine the half reactions of reactants undergoing oxidation and reduction. On adding the two half-reactions, net total equation can be obtained. This method of balancing redox reaction is known as half equation method.

The following rules must be followed in balancing redox reaction by half equation method:

1. Initially, redox reaction is separated into two half equations; oxidation and reduction.
2. Atoms other than hydrogen and oxygen are balanced first in the unbalanced half equations.
3. Oxygen atoms are balanced by addition of water on either side of the reaction.
4. Hydrogen ion/s is added to balance the hydrogen atom.
5. Electrons are added to balance the charge.
6. Half reactions are added to get the net total equation.
7. The further addition of hydroxide ion takes place on both side of the reaction, if the solution is basic in nature to neutralise the hydrogen ion present in the solution.

Answer to Problem 100AP

${\text{SiO}}_{\text{2}}\left(\text{s}\right)+4{\text{H}}^{+}\left(\text{a}\text{q}\right)+4{\text{e}}^{-}\to \text{Si}\left(\text{s}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$.

Explanation of Solution

The given half reaction is as follows:

${\text{SiO}}_{\text{2}}\left(\text{s}\right)\to \text{Si}\left(\text{s}\right)$

In the above reaction, add 2 water molecules to the right to balance the number of oxygen atoms:

${\text{SiO}}_{\text{2}}\left(\text{s}\right)\to \text{Si}\left(\text{s}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Now, add 4 hydrogen ions to the left to balance the hydrogen atoms,

${\text{SiO}}_{\text{2}}\left(\text{s}\right)+4{\text{H}}^{+}\left(\text{a}\text{q}\right)\to \text{Si}\left(\text{s}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

To balance the charge add 4 electrons to the left side of the reaction arrow thus,

${\text{SiO}}_{\text{2}}\left(\text{s}\right)+4{\text{H}}^{+}\left(\text{a}\text{q}\right)+4{\text{e}}^{-}\to \text{Si}\left(\text{s}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

The above reaction is balanced half reaction.

Interpretation Introduction

(b)

Interpretation:

The given half reaction should be balanced

Concept Introduction:

The oxidation-reduction reaction is also known as a redox reaction. In this reaction, one reactant is oxidized and other is reduced. In balancing an oxidation-reduction reaction, they must be first divided into two half reactions: one is oxidation reaction and other is reduction reaction.

The balancing of redox reaction is complicated as compared to simple balancing. It is necessary to determine the half reactions of reactants undergoing oxidation and reduction. On adding the two half-reactions, net total equation can be obtained. This method of balancing redox reaction is known as half equation method.

The following rules must be followed in balancing redox reaction by half equation method:

1. Initially, redox reaction is separated into two half equations; oxidation and reduction.
2. Atoms other than hydrogen and oxygen are balanced first in the unbalanced half equations.
3. Oxygen atoms are balanced by addition of water on either side of the reaction.
4. Hydrogen ion/s is added to balance the hydrogen atom.
5. Electrons are added to balance the charge.
6. Half reactions are added to get the net total equation.
7. The further addition of hydroxide ion takes place on both side of the reaction, if the solution is basic in nature to neutralise the hydrogen ion present in the solution.

Answer to Problem 100AP

$\text{S}\left(\text{s}\right)+2{\text{H}}^{+}+2{\text{e}}^{-}\to {\text{H}}_{\text{2}}\text{S}\left(\text{a}\text{q}\right)$.

Explanation of Solution

The given half reaction is as follows:

$\text{S}\left(\text{s}\right)\to {\text{H}}_{\text{2}}\text{S}\left(\text{a}\text{q}\right)$

In the above reaction, add 2 hydrogen ions to the left to balance the hydrogen atoms.

$\text{S}\left(\text{s}\right)+2{\text{H}}^{+}\to {\text{H}}_{\text{2}}\text{S}\left(\text{a}\text{q}\right)$

To balance the charge add two electrons to the left:

$\text{S}\left(\text{s}\right)+2{\text{H}}^{+}+2{\text{e}}^{-}\to {\text{H}}_{\text{2}}\text{S}\left(\text{a}\text{q}\right)$

The above half reaction is balanced.

Interpretation Introduction

(c)

Interpretation:

The given half reaction should be balanced

Concept Introduction:

The oxidation-reduction reaction is also known as a redox reaction. In this reaction, one reactant is oxidized and other is reduced. In balancing an oxidation-reduction reaction, they must be first divided into two half reactions: one is oxidation reaction and other is reduction reaction.

The balancing of redox reaction is complicated as compared to simple balancing. It is necessary to determine the half reactions of reactants undergoing oxidation and reduction. On adding the two half-reactions, net total equation can be obtained. This method of balancing redox reaction is known as half equation method.

The following rules must be followed in balancing redox reaction by half equation method:

1. Initially, redox reaction is separated into two half equations; oxidation and reduction.
2. Atoms other than hydrogen and oxygen are balanced first in the unbalanced half equations.
3. Oxygen atoms are balanced by addition of water on either side of the reaction.
4. Hydrogen ion/s is added to balance the hydrogen atom.
5. Electrons are added to balance the charge.
6. Half reactions are added to get the net total equation.
7. The further addition of hydroxide ion takes place on both side of the reaction, if the solution is basic in nature to neutralise the hydrogen ion present in the solution.

Answer to Problem 100AP

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)+3{\text{H}}^{+}\left(\text{a}\text{q}\right)+2{\text{e}}^{-}\to {\text{HNO}}_2\left(\text{a}\text{q}\right)+{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$.

Explanation of Solution

The given half reaction is as follows:

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)\to {\text{HNO}}_2\left(\text{a}\text{q}\right)$

In the above reaction, add 1 water molecule to the right to balance the number of oxygen atoms first.

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)\to {\text{HNO}}_2\left(\text{a}\text{q}\right)+{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Add 3 hydrogen ions to the left to balance the hydrogen atoms,

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)+3{\text{H}}^{+}\left(\text{a}\text{q}\right)\to {\text{HNO}}_2\left(\text{a}\text{q}\right)+{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Last step is to balance the charge, thus, 2 electrons are added to left side of the reaction arrow:

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)+3{\text{H}}^{+}\left(\text{a}\text{q}\right)+2{\text{e}}^{-}\to {\text{HNO}}_2\left(\text{a}\text{q}\right)+{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

The above half reaction is balanced.

Interpretation Introduction

(d)

Interpretation:

The given half reaction should be balanced

Concept Introduction:

The oxidation-reduction reaction is also known as a redox reaction. In this reaction, one reactant is oxidized and other is reduced. In balancing an oxidation-reduction reaction, they must be first divided into two half reactions: one is oxidation reaction and other is reduction reaction.

The balancing of redox reaction is complicated as compared to simple balancing. It is necessary to determine the half reactions of reactants undergoing oxidation and reduction. On adding the two half-reactions, net total equation can be obtained. This method of balancing redox reaction is known as half equation method.

The following rules must be followed in balancing redox reaction by half equation method:

1. Initially, redox reaction is separated into two half equations; oxidation and reduction.
2. Atoms other than hydrogen and oxygen are balanced first in the unbalanced half equations.
3. Oxygen atoms are balanced by addition of water on either side of the reaction.
4. Hydrogen ion/s is added to balance the hydrogen atom.
5. Electrons are added to balance the charge.
6. Half reactions are added to get the net total equation.
7. The further addition of hydroxide ion takes place on both side of the reaction, if the solution is basic in nature to neutralise the hydrogen ion present in the solution.

Answer to Problem 100AP

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)+4{\text{H}}^{+}\left(\text{a}\text{q}\right)+3{\text{e}}^{-}\to \text{NO}\left(\text{g}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$.

Explanation of Solution

The given half reaction is as follows:

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)\to \text{NO}\left(\text{g}\right)$

To balance the above reaction, add 2 water molecules to right side of the reaction arrow.

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)\to \text{NO}\left(\text{g}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Now, hydrogen atoms can be balanced by adding 4 hydrogen ions to the left side of the reaction arrow:

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)+4{\text{H}}^{+}\left(\text{a}\text{q}\right)\to \text{NO}\left(\text{g}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Last step is to balance the charge,

Thus, 3 electrons are added to left side of the reaction arrow and balanced half reaction will be:

${\text{NO}}_3{}^{-}\left(\text{a}\text{q}\right)+4{\text{H}}^{+}\left(\text{a}\text{q}\right)+3{\text{e}}^{-}\to \text{NO}\left(\text{g}\right)+2{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$.