State the kind of chemical reactions in the following examples:
$(a)$ Digestion of food in the stomach
$(b)$ Combustion of coal in air.

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

Give a reason why:
$(i)$ Why is a decomposition reaction called the opposite of a combination reaction?

In which of the following chemical equations,the abbreviations represent the correct states of the reactants and products involved at reaction temperature?

Write a balanced chemical equation for each of the following reactions and also classify them.
$(a)$ Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.
$(b)$ $A$ piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.

Which among the following changes are exothermic or endothermic in nature?
$(a)$ Decomposition of ferrous sulphate
$(b)$ Dilution of sulphuric acid
$(c)$ Dissolution of sodium hydroxide in water
$(d)$ Dissolution of ammonium chloride in water