Acid + Metal oxide $\longrightarrow$ ?

If the $pH$ of the aqueous solutions $A, B, C$ and $D$ are $1.9, 2.5, 2.1$ and $3.0$ respectively,then what will be the order of acidity?

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

Write true or false for the following statement:
Acids that give rise to more $H^+$ ions are said to be strong acids,and acids that give less $H^+$ ions are said to be weak acids.

Write true or false for the following statement:
Mixing an acid or base with water results in an increase in the concentration of ions $(H_{3}O^{+} / OH^{-})$ per unit volume.

How many moles are there in $4.9 \ g$ of $H_{2}SO_{4}$?