Redox Reactions — Prelims Questions

What is the oxidation state of sulfur in $Na_2S_2O_3$ (sodium thiosulfate)?

Which of the following reactions is an example of a disproportionation reaction?

In the reaction $MnO_4^- + C_2O_4^{2-} + H^+ \rightarrow Mn^{2+} + CO_2 + H_2O$, what is the stoichiometric coefficient for $C_2O_4^{2-}$ when the equation is balanced in acidic medium?

Which of the following statements about oxidizing and reducing agents is INCORRECT?

What is the oxidation state of nitrogen in $NH_4NO_3$?

When $K_2Cr_2O_7$ acts as an oxidizing agent in acidic medium, what is the change in the oxidation state of chromium?

Balance the following reaction in basic medium: $P_4(s) + OH^-(aq) + H_2O(l) \rightarrow PH_3(g) + H_2PO_2^-(aq)$. What is the coefficient for $OH^-$?