When hydrogen gas burns in the presence of oxygen,water is formed,and when water is electrolysed,hydrogen and oxygen gases are produced. State the kind of reaction that takes place:
$(a)$ In the first case
$(b)$ In the second case

You are provided with two containers made of copper and aluminium. You are also provided with solutions of dilute $HCl$,dilute $HNO_{3}$,$ZnCl_{2}$,and $H_{2}O$. In which of the above containers can these solutions be kept?

Why is a combustion reaction considered an oxidation reaction?

What happens when hydrogen gas is passed over heated copper oxide $(CuO)$?

Identify the oxidising agent (oxidant) in the following reactions:
$(a) Pb_{3}O_{4} + 8HCl \longrightarrow 3PbCl_{2} + Cl_{2} + 4H_{2}O$
$(b) 2Mg + O_{2} \longrightarrow 2MgO$
$(c) CuSO_{4} + Zn \longrightarrow Cu + ZnSO_{4}$
$(d) V_{2}O_{5} + 5Ca \longrightarrow 2V + 5CaO$
$(e) 3Fe + 4H_{2}O \longrightarrow Fe_{3}O_{4} + 4H_{2}$
$(f) CuO + H_{2} \longrightarrow Cu + H_{2}O$

Which one of the following processes involves chemical reactions?