Which of the following phenomena occur when a small amount of acid is added to water?
$(i)$ Ionisation
(ii) Neutralisation
(iii) Dilution
(iv) Salt formation

Write the balanced chemical equations for the following reactions:
$(a)$ Chlorine is passed over dry slaked lime.
$(b)$ Sodium bicarbonate reacts with dilute hydrochloric acid.
$(c)$ Sodium bicarbonate is heated.

Sodium hydrogencarbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved?
$(i)$ It turns lime water milky
$(ii)$ It extinguishes a burning splinter
$(iii)$ It dissolves in a solution of sodium hydroxide
$(iv)$ It has a pungent odour

$A$ dry pellet of a common base $B$,when kept in open,absorbs moisture and turns sticky. The compound is also a by-product of the chlor-alkali process. Identify $B$. What type of reaction occurs when $B$ is treated with an acidic oxide? Write a balanced chemical equation for one such reaction.

Match the chemical substances given in Column $(A)$ with their appropriate application given in Column $(B)$.

Column $(A)$	Column $(B)$
$(A)$ Bleaching powder	$(i)$ Preparation of glass
$(B)$ Baking soda	$(ii)$ Production of $H_2$ and $Cl_2$
$(C)$ Washing soda	$(iii)$ Decolourisation
$(D)$ Sodium chloride	$(iv)$ Antacid

What effect does dihydrogen gas $(H_2)$ have on litmus paper?