In which of the following reactions is there no change in the valency (oxidation state) of the elements?

Which of the following combinations does not evolve $Cl_2$ gas?

The number of moles of $KMnO_4$ reduced by $1 \ mol$ of $KI$ in basic medium is .............

In neutral or faintly alkaline medium,$MnO_4^{-}$ oxidizes $I^{-}$ to iodate. What is the volume (in $L$) of $0.02 \ M \ KMnO_4$ required to completely convert $1 \ L$ of $0.5 \ M \ KI$ solution to iodate in neutral or faintly alkaline medium?

Balance the following equations in basic medium by the ion-electron method and identify the oxidising agent and the reducing agent.
$(a)$ $P_{4(s)} + OH^{-}_{(aq)} \rightarrow PH_{3(g)} + H_{2}P{O_{2}}^{-}_{(aq)}$
$(b)$ $N_{2}H_{4(l)} + Cl{O_{3}}^{-}_{(aq)} \rightarrow NO_{(g)} + Cl^{-}_{(g)}$
$(c)$ $Cl_{2}O_{7(g)} + H_{2}O_{2(aq)} \rightarrow Cl{O_{2}}^{-}_{(aq)} + O_{2(g)} + H^{+}_{(aq)}$

Assign $A, B, C, D$ for the given type of reaction:
$Mn(NO_3)_2 + 2NaOH \longrightarrow Mn(OH)_2 \downarrow + 2NaNO_3$