Average Oxidation State of Chlorine from Ozonolysis

When chlorine dioxide ($\text{ClO}_2$) undergoes ozonolysis (reaction with ozone, $\text{O}_3$), it is oxidized to dichlorine hexoxide ($\text{Cl}_2\text{O}_6$):

$2\text{ClO}_2 + 2\text{O}_3 \longrightarrow \text{Cl}_2\text{O}_6 + 2\text{O}_2$

In the resulting oxide, $\text{Cl}_2\text{O}_6$: Let the average oxidation state of chlorine be $x$. Since the oxidation state of each oxygen atom is $-2$:

$2x + 6(-2) = 0$ $2x - 12 = 0 \implies x = +6$

(Note: In the solid state, $\text{Cl}_2\text{O}_6$ exists as the mixed-valence ionic compound $[\text{ClO}_2]^+[\text{ClO}_4]^-$, where the individual oxidation states of chlorine are $+5$ and $+7$, giving an average oxidation state of $\frac{+5 + (+7)}{2} = +6$.)

Therefore, the average oxidation state of chlorine in this oxide is 6.