When $Cu$ reacts with $AgNO_3$ solution,the reaction that takes place is:

In the reaction $8 \ Al + 3 \ Fe_3O_4 \to 4 \ Al_2O_3 + 9 \ Fe$,the number of moles of electrons transferred by $1 \ mol$ of reductant is:

If an atom undergoes reduction,its oxidation number......

Identify the redox couples involved in the following reactions:
$(a) \ Cu + Zn^{+2} \to Cu^{+2} + Zn$
$(b) \ Mg + Fe^{+2} \to Mg^{+2} + Fe$
$(c) \ Br_{2} + 2Cl^{-} \to Cl_{2} + 2Br^{-}$
$(d) \ Fe + Cd^{+2} \to Cd + Fe^{+2}$

Observe the following reactions:
$I$. $2H_2O_{(l)} + 2Na_{(s)} \rightarrow 2NaOH_{(aq)} + H_{2(g)}$
$II$. $2H_2O_{(l)} + 2F_{2(g)} \rightarrow 4H^{+}_{(aq)} + 4F^{-}_{(aq)} + O_{2(g)}$
Identify the correct statement from the following:

For the reaction $Ag_2O + H_2O + 2e^- \to 2Ag + 2OH^-$,which of the following is true?