Chapter 17, Problem 5PE

(a)

Interpretation Introduction

Interpretation:

Oxidation number of $\text{Cr}$ in ${\text{Na}}_2{\text{CrO}}_4$ has to be determined.

Concept Introduction:

Oxidation number is integer value allotted to every element. It is formal charge occupied by atom if all of its bonds are dissociated heterolytically. Below mentioned are rules to assign oxidation numbers to various elements.

1. Elements present in their free state have zero oxidation number.

2. Oxidation number of hydrogen is generally $+1$, except for metal hydrides.

3. Oxidation number of oxygen is $-2$, except for peroxides.

4. Metals have positive oxidation numbers.

5. Negative oxidation numbers are assigned to most electronegative element in covalent compounds.

6. Sum of oxidation numbers of different elements in neutral atom is zero.

7. Sum of oxidation numbers of various elements in polyatomic ion is equal to charge present on ion.

(b)

Interpretation Introduction

Interpretation:

Oxidation number of $\text{Fe}$ in ${\text{K}}_3\left[\text{Fe}{\left(\text{CN}\right)}_6\right]$ has to be determined.

Concept Introduction:

Refer to part (a).

(c)

Interpretation Introduction

Interpretation:

Oxidation number of $\text{Co}$ and $\text{Cl}$ in ${\text{CoCl}}_2$ has to be determined.

Concept Introduction:

Refer to part (a).

(d)

Interpretation Introduction

Interpretation:

Oxidation number of $\text{Ni}$ in ${\text{NiCl}}_2\cdot {\text{6H}}_2\text{O}$ has to be determined.

Concept Introduction:

Refer to part (a).