The $pH$ scale is applicable to which of the following?

$(i)$ 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?

Which of the following salts has a $pH$ less than $7$? Why?

What effect does an increase in the concentration of $H^{+}(aq)$ in a solution have on the $pH$ of the solution?

You have two solutions $A$ and $B$. The $pH$ of solution $A$ is $6$ and the $pH$ of solution $B$ is $8$. Which solution has more hydrogen ion concentration? Which one of these is acidic and which one is basic?

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