Chapter 20.2, Problem 10SP

(a)

Interpretation Introduction

Interpretation: The oxidation number of ${\text{S}}_{\text{2}}{\text{O}}_{\text{3}}$ is to be determined.

Concept Introduction: The zero, positive or negative numbers that are assigned to an atom for indicating its degree of oxidation and reduction is the oxidation number. This number indicates the number of electrons that are either gained or lost during the bond formation in a chemical compound.

Certain rules must be followed to get the oxidation number of elements in a chemical compound. They are,

• The oxidation number of oxygen is $-\text{2}$ .
• For a neutral compound, the total sum of the oxidation number is zero.
• For ionic compounds with a charge, the total sum of oxidation number is equal to its charge.

Answer to Problem 10SP

The oxidation number of sulfur in ${\text{S}}_{\text{2}}{\text{O}}_{\text{3}}$ is $+3$ .

Explanation of Solution

The given compound ${\text{S}}_{\text{2}}{\text{O}}_{\text{3}}$ is neutral. So, the total sum of oxidation numbers is equal to zero. And also the oxidation number of oxygen is $-\text{2}$ .

Let $x$ be the oxidation number of $\text{S}$ , then according to the rule,

  $\begin{array}{c}2x+3\times -2=0\\ 2x-6=0\\ 2x=6\\ x=3\end{array}$

So, the oxidation number of sulfur, $\text{S}$ in ${\text{S}}_{\text{2}}{\text{O}}_{\text{3}}$ is $+3$ .

(b)

Interpretation Introduction

Interpretation: The oxidation number of ${\text{Na}}_{\text{2}}{\text{O}}_2$ is to be determined.

Concept Introduction: The zero, positive or negative numbers that are assigned to an atom for indicating its degree of oxidation and reduction is the oxidation number. This number indicates the number of electrons that are either gained or lost during the bond formation in a chemical compound.

Certain rules must be followed to get the oxidation number of elements in a chemical compound. They are,

• The oxidation number of oxygen is $-\text{2}$ .
• For a neutral compound, the total sum of the oxidation number is zero.
• For ionic compounds with a charge, the total sum of oxidation number is equal to its charge.

Answer to Problem 10SP

The oxidation number of sodium in ${\text{Na}}_{\text{2}}{\text{O}}_2$ is $+\text{2}$ .

Explanation of Solution

The given compound ${\text{Na}}_{\text{2}}{\text{O}}_2$ is neutral. So, the total sum of the oxidation number is zero. And the oxidation number of oxygen is $-\text{2}$ .

Let $x$ be the oxidation number of sodium, $\text{Na}$ .

  $\begin{array}{c}2x+2\times -2=0\\ 2x-4=0\\ 2x=4\\ x=2\end{array}$

So, the oxidation number of sodium is $+\text{2}$ .

(c)

Interpretation Introduction

Interpretation: The oxidation number of ${\text{P}}_{\text{2}}{\text{O}}_5$ is to be determined.

Concept Introduction: The zero, positive or negative numbers that are assigned to an atom for indicating its degree of oxidation and reduction is the oxidation number. This number indicates the number of electrons that are either gained or lost during the bond formation in a chemical compound.

Certain rules must be followed to get the oxidation number of elements in a chemical compound. They are,

• The oxidation number of oxygen is $-\text{2}$ .
• For a neutral compound, the total sum of the oxidation number is zero.
• For ionic compounds with a charge, the total sum of oxidation number is equal to its charge.

Answer to Problem 10SP

The oxidation number of sodium in ${\text{P}}_{\text{2}}{\text{O}}_5$ is $+5$ .

Explanation of Solution

The given compound ${\text{P}}_{\text{2}}{\text{O}}_5$ is neutral. So, the total sum of the oxidation number is zero. And the oxidation number of oxygen is $-\text{2}$ .

Let $x$ be the oxidation number of phosphorus, $\text{P}$ .

  $\begin{array}{c}2x+5\times \left(-2\right)=0\\ 2x-10=0\\ 2x=10\\ x=5\end{array}$

So, the oxidation number of phosphorus in ${\text{P}}_{\text{2}}{\text{O}}_5$ is $+5$ .

(d)

Interpretation Introduction

Interpretation: The oxidation number of ${\text{NO}}_3{}^{-}$ is to be determined.

Concept Introduction: The zero, positive or negative numbers that are assigned to an atom for indicating its degree of oxidation and reduction is the oxidation number. This number indicates the number of electrons that are either gained or lost during the bond formation in a chemical compound.

Certain rules must be followed to get the oxidation number of elements in a chemical compound. They are,

• The oxidation number of oxygen is $-\text{2}$ .
• For a neutral compound, the total sum of the oxidation number is zero.
• For ionic compounds with a charge, the total sum of oxidation number is equal to its charge.

Answer to Problem 10SP

The oxidation number of nitrogen in ${\text{NO}}_3{}^{-}$ is $+5$ .

Explanation of Solution

The given compound ${\text{NO}}_3{}^{-}$ is an ionic compound. So, the total number of oxidation numbers is equal to its charge.

Let $x$ be the oxidation number of nitrogen in ${\text{NO}}_3{}^{-}$ ,

  $\begin{array}{c}x+3\times \left(-2\right)=-1\\ x-6=-1\\ x=-1+6\\ x=5\end{array}$

So, the oxidation number of nitrogen is $+5$ .