$(i)$ State the purpose of developing $pH$ scale.
$(ii)$ Mention the $pH$ range for acids.
$(iii)$ What is the $pH$ of acid rain and how it affects the aquatic life?

(N/A) $(i)$ The purpose of developing the $pH$ scale was to quantify the concentration of $H^{+}$ or $OH^{-}$ ions in a solution.
$(ii)$ The $pH$ range for acidic solutions is $0$ to less than $7$.
$(iii)$ Acid rain is defined as rain water with a $pH$ value of less than $5.6$. When this acidic water flows into rivers and lakes,it lowers the $pH$ of the aquatic environment,making it difficult for aquatic organisms to survive.