When a manganous salt is fused with a mixture of $KNO_3$ and solid $NaOH$, the oxidation number of $Mn$ changes from $+2$ to:

For the following redox reaction, find the correct statement: $Sn^{2+} + 2Fe^{3+} \rightarrow Sn^{4+} + 2Fe^{2+}$

In acidic medium,the moles of $KMnO_4$ required to oxidize $1.5 \, mol$ of $Cu_2S$ will be ............... $mol$.

In the following reaction mixtures,
$I$. $Cu / CuSO_4 + Ag / Ag_2SO_4$
$II$. $Zn / ZnSO_4 + Cu / CuSO_4$
copper respectively undergoes

When mercury $(II)$ chloride is treated with an excess of $SnCl_2$, the products obtained are:

Suggest a scheme of classification of the following redox reactions:
$(a) N_{2(g)} + O_{2(g)} \rightarrow 2NO_{(g)}$
$(b) 2Pb(NO_3)_{2(s)} \rightarrow 2PbO_{(s)} + 4NO_{2(g)} + O_{2(g)}$
$(c) NaH_{(s)} + H_2O_{(l)} \rightarrow NaOH_{(aq)} + H_{2(g)}$
$(d) 2NO_{2(g)} + 2OH^{-}_{(aq)} \rightarrow NO_2^-(aq) + NO_3^-(aq) + H_2O_{(l)}$