Which among the following is not a base?

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

$Na_{2}CO_{3} \cdot 10H_{2}O$ and $Na_{2}CO_{3}$ are two chemical compounds. Write their chemical names. Explain the significance of $10H_{2}O$ and mention the term used for water molecules attached to a salt.

Give reasons for the following:
$(a)$ Dry $HCl$ gas does not change the colour of dry litmus paper.

What happens when a solution of an acid is mixed with a solution of a base in a test tube?
$(i)$ The temperature of the solution increases
$(ii)$ The temperature of the solution decreases
$(iii)$ The temperature of the solution remains the same
$(iv)$ Salt formation takes place

Identify the correct representation of the reaction occurring during the chlor-alkali process.