Chapter 21, Problem 103A

(a)

Interpretation Introduction

Interpretation: The oxidation number of sulfur in ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ needs to be determined.

Concept Introduction: An oxidation number of an element is defined as the number assigned to it in any chemical composition representing number of electrons gained or lost by an atom of that element in forming the chemical compound.

Explanation of Solution

The given molecule is ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$ . Here, the oxidation number of H and O is 1 and -2 respectively. Thus, oxidation state of S can be calculated as follows:

  $\begin{array}{l}2\left(1\right)+x+4\left(-2\right)=0\\ 2+x-8=0\\ x=8-2\\ x=+6\end{array}$

Thus, oxidation number of S is +6.

(b)

Interpretation Introduction

Interpretation: The oxidation number of sulfur in ${\text{H}}_{\text{2}}\text{S}$ needs to be determined.

Concept Introduction: An oxidation number of an element is defined as the number assigned to it in any chemical composition representing number of electrons gained or lost by an atom of that element in forming the chemical compound.

Explanation of Solution

The given molecule is ${\text{H}}_{\text{2}}\text{S}$ . Here, oxidation number of H is 1. Thus, oxidation number of S can be calculated as follows:

  $\begin{array}{c}2\left(1\right)+x=0\\ x=-2\end{array}$

Thus, oxidation number of S is -2.

(c)

Interpretation Introduction

Interpretation: The oxidation number of sulfur in ${\text{SO}}_2$ needs to be determined.

Concept Introduction: An oxidation number of an element is defined as the number assigned to it in any chemical composition representing number of electrons gained or lost by an atom of that element in forming the chemical compound.

Explanation of Solution

The given molecule is ${\text{SO}}_2$ . Here, oxidation number of O is -2. Thus, oxidation number of S can be calculated as follows:

  $\begin{array}{l}x+2\left(-2\right)=0\\ x-4=0\\ x=4\end{array}$

Thus, oxidation number of S is +4.

(d)

Interpretation Introduction

Interpretation: The oxidation number of sulfur in ${\text{Na}}_{\text{2}}{\text{S}}_2{\text{O}}_3$ needs to be determined.

Concept Introduction: An oxidation number of an element is defined as the number assigned to it in any chemical composition representing number of electrons gained or lost by an atom of that element in forming the chemical compound.

Explanation of Solution

The given molecule is ${\text{Na}}_{\text{2}}{\text{S}}_2{\text{O}}_3$ . Here, the oxidation number of Na and O is +1 and -2 respectively. Thus, the oxidation number of S can be calculated as follows:

  $\begin{array}{l}2\left(+1\right)+2x+3\left(-2\right)=0\\ 2+2x-6=0\\ 2x-4=0\\ x=2\end{array}$

Thus, oxidation number of S is +2.

(e)

Interpretation Introduction

Interpretation: The oxidation number of sulfur in $\text{S}$ needs to be determined.

Concept Introduction: An oxidation number of an element is defined as the number assigned to it in any chemical composition representing number of electrons gained or lost by an atom of that element in forming the chemical compound.

Explanation of Solution

The oxidation number of S in monoatomic form will be zero.

Here, no other atom is present if oxidation number of S is considered as x , the calculation step will be:

  $x=0$

(f)

Interpretation Introduction

Interpretation: The oxidation number of sulfur in ${\text{SO}}_3^{2-}$ needs to be determined.

Concept Introduction: An oxidation number of an element is defined as the number assigned to it in any chemical composition representing number of electrons gained or lost by an atom of that element in forming the chemical compound.

Explanation of Solution

The oxidation number of oxygen is -2. Thus, oxidation number of S can be calculated as follows:

  $\begin{array}{l}x+3\left(-2\right)=-2\\ x-6=-2\\ x=-2+6\\ x=4\end{array}$

Thus, the oxidation number of S is +4.