6K.5 a

[Jessica Booth 2F]

How do you know that O3 is oxidized?

[Katherine Wu 1H]

O3 (g) →O2(g)
O3(g) →O2(g)+H2O(l) (balances O)
2H2O(l)+O3(g) →O2(g)+H2O(l)+2OH^-(aq) (balances H)
H2O(l)+O3(g) →O2(g)+2OH^-(aq) (cancels H2O)
H2O(l)+O3(g)+2e- →O2(g)+2OH^-(aq) (balances charge)

Br^-(aq) →BeO3^-(aq)
3H2O(l)+Br^-(aq) →BrO3^- (balances O)
6OH^-(aq)+3H2O(l)+Br^-(aq) →BrO3^-(aq)+^H2O(l) (balances H)
6OH^-(aq)+3H2O(l)+Br^-(aq) →BrO3^-(aq)+6H2O(l)+6e- (balances charge)

Combining half-rxns yields
3[H2O(l)+O3(g)+2e- →O2(g)+2OH^-(aq)]
6OH^-(aq)+3H2O(l)+Br^-(aq) →BrO3^-(aq)+6H2O(l)+6e-
6H2O(l)+3O3(g)+6OH^-(aq)+Br^-(aq)+6e- →3O2(g)+6OH^-(aq)+BrO3^-(aq)+6H2O(l)+6e-
and
3O3(g)+Br^-(aq) →3O2(g)+BrO3^-(aq)
O3 is the oxidizing agent and Br^- is the reducing agent.