What is the molarity of a solution prepared by dissolving $8 \ g$ of $NaOH$ in water to make a total volume of $100 \ mL$ (in $M$)?

Explain why:
$(a)$ the colour of copper sulphate crystals changes on heating?
$(b)$ baking soda acts as an antacid?
$(c)$ an acid should be added to water while diluting?

Make the correct pairs from below mentioned $'X'$ and $'Y':$

$1. \text{Sulphurous acid}$	$p. H_{3}PO_{4}$
$2. \text{Sulphuric acid}$	$q. H_{2}S_{2}O_{7}$
$3. \text{Oleum}$	$r. H_{2}SO_{3}$
$4. \text{Phosphoric acid}$	$s. H_{2}SO_{4}$

Identify $A, B$ and $C$ in the following reactions and write the chemical name of $A, B$ and $C$.
$(i)$ $HNO_{3} + NaOH \rightarrow \underline{A} + H_{2}O$
$(ii)$ $\underline{B} + Ca(OH)_{2} \rightarrow CaSO_{4} + 2H_{2}O$
$(iii)$ $HCl + \underline{C} \rightarrow KCl + H_{2}O$

$A$ dry pellet of a common base $B$,when kept in open,absorbs moisture and turns sticky. The compound is also a by-product of the chlor-alkali process. Identify $B$. What type of reaction occurs when $B$ is treated with an acidic oxide? Write a balanced chemical equation for one such reaction.

Which of the following cannot be used as an antacid for the treatment of acidity?