Name the oxidising and reducing agent in the following reaction:
$CuO + H_{2} \longrightarrow Cu + H_{2}O$

Which of the following statements about the given reaction are correct?
$3 Fe (s) + 4 H_2 O (g) \rightarrow Fe_3 O_4 (s) + 4 H_2 (g)$
$(i)$ Iron metal is getting oxidised
$(ii)$ Water is getting reduced
$(iii)$ Water is acting as reducing agent
$(iv)$ Water is acting as oxidising agent

Why is a combustion reaction considered an oxidation reaction?

Which is the reducing agent in the following reaction?
$MnO_{2}(s) + 4HCl(aq) \longrightarrow MnCl_{2}(s) + 2H_{2}O(l) + Cl_{2}(g)$

$A$ shiny brown coloured element $X$ on heating in air becomes black in colour. Name the element $X$ and the black coloured compound formed.

If copper metal is heated over a flame, it develops a coating. What is the colour and composition of this coating?