Chapter 18, Problem 18.78SP

(a)

Interpretation Introduction

Interpretation:

The balanced net ionic equation for oxidation of ${\text{I}}^{\text{-}}$ by ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$ to ${\text{I}}_{\text{2}}$ in acidic solution has to be written.

Concept Introduction:

Hydrogen peroxide act as both strong oxidising and reducing agent.  In aqueous solution it will act as weak acid, predominantly dissociates to gives ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ and ${\text{HO}}_{\text{2}}^{\text{-}}$ ions.

$\begin{array}{l}{\text{H}}_{\text{2}}{\text{O}}_{\text{2}\left(\text{aq}\right)}{\text{+2H}}^{\text{+}}{}_{\left(\text{aq}\right)}{\text{+2e}}^{\text{-}}\stackrel{}{\to }{\text{2H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\\ \\ {\text{H}}_{\text{2}}{\text{O}}_{\text{2}\left(\text{aq}\right)}\stackrel{}{\to }{\text{O}}_{\text{2}}{}_{\left(\text{g}\right)}{\text{+2H}}^{\text{+}}{}_{\left(\text{aq}\right)}{\text{+2e}}^{\text{-}}\end{array}$

(b)

Interpretation Introduction

Interpretation:

The balanced net ionic equation for reduction of ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}{}^{\text{2-}}$ by ${\text{H}}_{\text{2}}{\text{O}}_{\text{2}}$ to ${\text{Cr}}^{\text{3+}}$ in acidic solution has to be written.

Concept Introduction:

Hydrogen peroxide act as both strong oxidising and reducing agent.  In aqueous solution it will act as weak acid, predominantly dissociates to gives ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ and ${\text{HO}}_{\text{2}}^{\text{-}}$ ions.

$\begin{array}{l}{\text{H}}_{\text{2}}{\text{O}}_{\text{2}\left(\text{aq}\right)}{\text{+2H}}^{\text{+}}{}_{\left(\text{aq}\right)}{\text{+2e}}^{\text{-}}\stackrel{}{\to }{\text{2H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\\ \\ {\text{H}}_{\text{2}}{\text{O}}_{\text{2}\left(\text{aq}\right)}\stackrel{}{\to }{\text{O}}_{\text{2}}{}_{\left(\text{g}\right)}{\text{+2H}}^{\text{+}}{}_{\left(\text{aq}\right)}{\text{+2e}}^{\text{-}}\end{array}$