How is the concentration of a solution expressed in molarity?

How is bleaching powder prepared? Why does bleaching powder $(i)$ smell strongly of chlorine?

What will be the value of $pH$ if blue litmus paper turns red in an aqueous solution?

Equal lengths of magnesium ribbon are taken in two test tubes $A$ and $B$. $H_{2}SO_{4}$ is added to test tube $A$ and $H_{2}CO_{3}$ in test tube $B$ in equal amounts.
$(a)$ Identify the test tube showing vigorous reaction.
$(b)$ Give reason to support your answer.
$(c)$ Name the gas liberated in both the test tubes. How will you prove its liberation?

$NH_{4}Cl$ is a salt of which type?

Match the important chemicals given in Column $(A)$ with the chemical formulae given in Column $(B)$.

Column $(A)$	Column $(B)$
$(a)$ Plaster of Paris	$(i)$ $Ca(OH)_{2}$
$(b)$ Gypsum	$(ii)$ $CaSO_{4} \cdot 1/2 H_{2}O$
$(c)$ Bleaching Powder	$(iii)$ $CaSO_{4} \cdot 2H_{2}O$
$(d)$ Slaked Lime	$(iv)$ $CaOCl_{2}$