Oxidation Number Method — Prelims Questions

Balance the following redox reaction in acidic medium using the oxidation number method: $ext{MnO}_4^- + \text{C}_2\text{O}_4^{2-} \to \text{Mn}^{2+} + \text{CO}_2$

Which of the following statements about oxidation numbers is INCORRECT?

Balance the following redox reaction in basic medium using the oxidation number method: $ext{Cr}(\text{OH})_3 + \text{ClO}^- \to \text{CrO}_4^{2-} + \text{Cl}^-$

In the reaction: $ext{P}_4 + \text{OH}^- + \text{H}_2\text{O} \to \text{PH}_3 + \text{H}_2\text{PO}_2^-$, what is the oxidation number of phosphorus in $ext{PH}_3$ and $ext{H}_2\text{PO}_2^-$ respectively?

Which of the following elements can exhibit both positive and negative oxidation numbers?

In the disproportionation reaction of hydrogen peroxide: $2\text{H}_2\text{O}_2 \to 2\text{H}_2\text{O} + \text{O}_2$, what are the oxidation numbers of oxygen in the reactants and products?

Which of the following species acts as both an oxidizing and a reducing agent in different reactions?