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

Balance the following chemical equation:
$Fe(s) + H_2O(g) \rightarrow Fe_3O_4(s) + H_2(g)$

Observe the following diagram and answer the questions that follow:
$(i)$ Identify the gases evolved at anode and cathode.
$(ii)$ Why are the amounts of gases collected in the two test tubes not of the same volume?
$(iii)$ What type of reaction is this?
$(iv)$ Why should we use salt water?

State what happens when:
$(a)$ Gypsum is heated at $373 \, K$.
Also,write the chemical equation for the reaction.

Why is a combustion reaction considered an oxidation reaction?

$A$ solution of potassium chloride when mixed with silver nitrate solution,an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of the chemical reaction?