Chapter 20, Problem 23QRT

(a)

Interpretation Introduction

Interpretation:

Oxidation state of the transition metal in ${\text{V}}_2{\text{O}}_5$ has to be determined.

Explanation of Solution

Given compound is ${\text{V}}_2{\text{O}}_5$.  The transition metal that is present in the given compound is vanadium.  In any neutral compound, the total number of oxidation state of all the elements present in it is equal to zero.  Oxidation number of oxygen is $-2$.  Therefore, the oxidation state of vanadium in the given compound can be determined as shown below,

    $\begin{array}{l}{\text{V}}_2{\text{O}}_5:\\ 2(x)+5(-2)=0\\ 2x-10=0\\ 2x=10\\ x=5\end{array}$

Therefore, the oxidation state of vanadium in ${\text{V}}_2{\text{O}}_5$ is $+5$.

(b)

Interpretation Introduction

Interpretation:

Oxidation state of the transition metal in ${\text{K}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}$ has to be determined.

Explanation of Solution

Given compound is ${\text{K}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}$.  The transition metal that is present in the given compound is chromium.  In any neutral compound, the total number of oxidation state of all the elements present in it is equal to zero.  Oxidation state of potassium is $+1$ and that of oxygen is $-2$.  Therefore, the oxidation state of chromium in the given compound can be determined as shown below,

    $\begin{array}{l}{\text{K}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}:\\ 2(+1)+2(x)+7(-2)=0\\ 2+2x-14=0\\ 2x-12=0\\ x=6\end{array}$

Therefore, the oxidation state of chromium in ${\text{K}}_{\text{2}}{\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}$ is $+6$.

(c)

Interpretation Introduction

Interpretation:

Oxidation state of the transition metal in ${\text{MnO}}_{\text{2}}$ has to be determined.

Explanation of Solution

Given compound is ${\text{MnO}}_{\text{2}}$.  The transition metal that is present in the given compound is manganese.  In any neutral compound, the total number of oxidation state of all the elements present in it is equal to zero.  Oxidation state of oxygen is $-2$.  Therefore, the oxidation state of manganese in the given compound can be determined as shown below,

    $\begin{array}{l}{\text{MnO}}_{\text{2}}:\\ 1(x)+2(-2)=0\\ 2x-4=0\\ 2x=4\\ x=2\end{array}$

Therefore, the oxidation state of manganese in ${\text{MnO}}_{\text{2}}$ is $+2$.

(d)

Interpretation Introduction

Interpretation:

Oxidation state of the transition metal in ${\text{OsO}}_{\text{4}}$ has to be determined.

Explanation of Solution

Given compound is ${\text{OsO}}_{\text{4}}$.  The transition metal that is present in the given compound is osmium.  In any neutral compound, the total number of oxidation state of all the elements present in it is equal to zero.  Oxidation state of oxygen is $-2$.  Therefore, the oxidation state of osmium in the given compound can be determined as shown below,

    $\begin{array}{l}{\text{OsO}}_{\text{4}}:\\ 1(x)+4(-2)=0\\ 1x-8=0\\ x=8\end{array}$

Therefore, the oxidation state of osmium in ${\text{OsO}}_{\text{4}}$ is $+8$.