Which of the following salts does not contain water of crystallisation?

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

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 $H_{2}CO_{3}$ is added to test tube $B$ in equal amounts.
$(a)$ Write chemical equations for both the reactions.
$(b)$ Out of the two acids taken above,which one will have a lower $pH$ value and lower $H^{+}$ concentration,respectively?

Tooth enamel is the hardest substance in our body. Name the compound of which it is made up. At what $pH$ of the mouth does it get corroded? State the role of bacteria present in the mouth. Suggest a method to prevent tooth decay.

Fill in the missing data in the following table:

Name of the salt	Formula	Base	Acid
$(i)$ Ammonium chloride	$NH_{4}Cl$	$NH_{4}OH$	-
$(ii)$ Copper sulphate	-	-	$H_{2}SO_{4}$
$(iii)$ Sodium chloride	$NaCl$	$NaOH$	-
$(iv)$ Magnesium nitrate	$Mg(NO_{3})_{2}$	-	$HNO_{3}$
$(v)$ Potassium sulphate	$K_{2}SO_{4}$	-	-
$(vi)$ Calcium nitrate	$Ca(NO_{3})_{2}$	$Ca(OH)_{2}$	-

In a basic aqueous solution,how does the basicity of the solution change as the concentration of $[OH^{-}]$ ions decreases?