Chapter 8, Problem 8G.2E

(a)

Interpretation Introduction

Interpretation:

The oxidation number of white phosphorus has to be given.

Answer to Problem 8G.2E

The oxidation number of white phosphorus is zero.

Explanation of Solution

Phosphorus in its elemental state exists as white phosphorus and red phosphorus and its formula is ${\text{P}}_{\text{4}}\text{.}$  The oxidation number of white phosphorus is zero.

(b)

Interpretation Introduction

Interpretation:

The oxidation number of red phosphorus has to be given.

Answer to Problem 8G.2E

The oxidation number of red phosphorus is zero.

Explanation of Solution

Red phosphorus is the elemental state of phosphorus and its formula is ${\text{P}}_{\text{4}}\text{.}$  The oxidation number of red phosphorus is zero.

(c)

Interpretation Introduction

Interpretation:

The oxidation number of phosphorus in ${\text{Ca}}_{\text{5}}{\text{P}}_{\text{8}}$ has to be given.

Answer to Problem 8G.2E

The oxidation number of phosphorus in ${\text{Ca}}_{\text{5}}{\text{P}}_{\text{8}}$ is $\text{-1}\text{.25}\text{.}$

Explanation of Solution

Let x be the oxidation number of phosphorus in ${\text{Ca}}_{\text{5}}{\text{P}}_{\text{8}}.$  The oxidation number of calcium is +2.  The oxidation number of phosphorus is calculated as,

  $\begin{array}{l}\text{5}\left(\text{+2}\right)\text{+8}\left(\text{x}\right)\text{=0}\\ \text{10+8x=0}\\ \text{8x=-10}\\ \text{x=-1}\text{.25}\end{array}$

The oxidation number of phosphorus in ${\text{Ca}}_{\text{5}}{\text{P}}_{\text{8}}$ is $\text{-1}\text{.25}\text{.}$

(d)

Interpretation Introduction

Interpretation:

The oxidation number of phosphorus in ${\text{PH}}_{\text{4}}\text{I}$ has to be given.

Answer to Problem 8G.2E

The oxidation number of phosphorus in ${\text{PH}}_{\text{4}}\text{I}$ is $\text{-3}\text{.}$

Explanation of Solution

Let x be the oxidation number of phosphorus in ${\text{PH}}_{\text{4}}\text{I}\text{.}$  The oxidation number of phosphorus is calculated as,

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

The oxidation number of phosphorus in ${\text{PH}}_{\text{4}}\text{I}$ is $\text{-3}\text{.}$

(e)

Interpretation Introduction

Interpretation:

The oxidation number of phosphorus in ${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{\text{-}}$ has to be given.

Answer to Problem 8G.2E

The oxidation number of phosphorus in ${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{\text{-}}$ is $\text{+5}\text{.}$

Explanation of Solution

Let x be the oxidation number of phosphorus in ${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{\text{-}}.$  The oxidation number of phosphorus is calculated as,

  $\begin{array}{l}\text{2}\left(\text{+1}\right)\text{+x+4}\left(\text{-2}\right)\text{=0}\\ \text{2+x-8=-1}\\ \text{x-6=-1}\\ \text{x=-1+6}\\ \text{x=+5}\end{array}$

The oxidation number of phosphorus in ${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{\text{-}}$ is $\text{+5}\text{.}$

(f)

Interpretation Introduction

Interpretation:

The oxidation number of phosphorus in ${\text{P}}_{\text{5}}{\text{H}}_{\text{5}}$ has to be given.

Answer to Problem 8G.2E

The oxidation number of phosphorus in ${\text{P}}_{\text{5}}{\text{H}}_{\text{5}}$ is $\text{-1}\text{.}$

Explanation of Solution

Let x be the oxidation number of phosphorus in ${\text{P}}_{\text{5}}{\text{H}}_{\text{5}}.$  The oxidation number of phosphorus is calculated as,

  $\begin{array}{l}\text{5}\left(\text{x}\right)\text{+5}\left(\text{+1}\right)\text{=0}\\ \text{5x+5=0}\\ \text{5x=-5}\\ \text{x=-1}\end{array}$

The oxidation number of phosphorus in ${\text{P}}_{\text{5}}{\text{H}}_{\text{5}}$ is $\text{-1}\text{.}$

(g)

Interpretation Introduction

Interpretation:

The oxidation number of phosphorus in ${\text{P}}_{\text{2}}{\text{O}}_{\text{5}}$ has to be given.

Answer to Problem 8G.2E

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

Explanation of Solution

Let x be the oxidation number of phosphorus in ${\text{P}}_{\text{2}}{\text{O}}_{\text{5}}.$  The oxidation number of phosphorus is calculated as,

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

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