Write the essential condition for the following reaction to take place: $2 AgCl \rightarrow 2 Ag + Cl_{2}$ and write one use of this reaction.

State whether the following statement is true or false:
Calcium oxide is also called lime or quicklime.

Give reason why:
$(i)$ White coloured silver chloride turns grey when kept in sunlight.

Write balanced chemical equations for the following reactions:
$(i)$ Calcium carbonate on reaction with hydrochloric acid gives calcium chloride,water and carbon dioxide.
$(ii)$ Nitrogen reacts with hydrogen under pressure to form ammonia.
$(iii)$ Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.

Write two observations for the following chemical reaction:
$(a)$ Dilute sulphuric acid is poured over zinc granules.

Balance the following chemical equations:
$(a)$ $KClO_{3} \longrightarrow KCl + O_{2}$
$(b)$ $Na_{2}CO_{3} + HCl \longrightarrow NaCl + H_{2}O + CO_{2}$