Which one is a chemical change: Electrolysis of water or Sodium chloride exposed to sunlight?

Write a balanced chemical equation for the reaction in which phosphorus burns in chlorine to form phosphorus pentachloride.

Complete the missing components/variables given as $x$ and $y$ in the following reactions:
$(a)$ $Zn(s) + H_2SO_4(aq) \longrightarrow ZnSO_4(x) + H_2(y)$
$(b)$ $CaCO_3(s) \xrightarrow{x} CaO(s) + CO_2(g)$

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

The substances which get oxidised easily can be kept for longer duration by:

Which of the following are exothermic processes?
$(i)$ Reaction of water with quick lime
$(ii)$ Dilution of an acid
$(iii)$ Evaporation of water
$(iv)$ Sublimation of camphor (crystals)