(a) H₂O₂ + O₃ → H₂O + 2O₂ 

(b) H₂O₂ + Ag₂O → 2Ag + H₂O + O₂ 

The role of hydrogen peroxide in the above reactions is respectively:

A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the reaction which element undergoes maximum change in the oxidation number?Redox Reactions

1. S

2. H

3. Cl

4. C

Oxidation numbers of P in ${\mathrm{PO}}_4^{3-}$, of S in ${\mathrm{SO}}_4^{2-}$ and that of Cr in ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$are respectively:
1. +5, +6 and +6
2. +3, +6 and +5
3. +5, +3 and +6
4. -3, +6 and +6