How is the $pH$ of a solution of an acid influenced when it is diluted?

$(i)$ What is the $pH$ range for a base?
$(ii)$ How can the strength of a basic solution be increased?

$(a)$ What is a universal indicator?
$(b)$ Write the chemical equation involved in the preparation of sodium hydroxide. Name the process.

Who proposed the acid-base theory of ionization?

The metal salt $A$ is blue in colour. When salt $A$ is heated strongly over a burner,a substance $B$ present in it is eliminated and a white powder $C$ is left behind. When a few drops of a liquid $D$ are added to powder $C$,it becomes blue again.
$(a)$ Identify $A, B, C, D$.
$(b)$ Write the chemical equations involved.
$(c)$ Give an example of a salt which also shows the above property.

State the chemical property in each of the following cases,on which the following uses of baking soda are based:
$(a)$ Applied on an ant stung area.
$(b)$ As a constituent of baking powder.
$(c)$ In soda-acid fire extinguisher.