What happens when
a. Sodium metal is dropped in water?
b. Sodium metal is heated in free supply of air?
c. Sodium peroxide dissolves in water?

Explanation

(i) When sodium metal is dropped in water, hydrogen gas is evolved which catches fire due to exothermic nature of the reaction.
`2Na(s) + 2H_2O (l) to 2NaOH (aq) + H_2`
(ii) Sodium peroxide and sodium oxide is formed .
`2Na(s) + (1)/(2)O_2(g) to underset("(Minor product)")(Na_2O)(s)`
`Na_2O(s) +1//2O_2(g) to underset("(Major product)")(Na_2O_2)(s)`
(iii) When sodium peroxide is dissolved in water , hydrogen peroxide is formed.
`Na_2O_2(s) + 2H_2O (l) to 2NaOH (aq) + H_2O_2(l)`