Which of the following salts has a $pH$ less than $7$? Why?

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	$Ca(NO_{3})_{2}$	$Ca(OH)_{2}$	-

$A$ 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.

$(i)$ Give an example of a strong base and a weak base.

Three acidic solutions $A, B$ and $C$ have $pH = 0, 3$ and $5$ respectively.
$(i)$ Which solution has the highest concentration of $H^{+}$ ions?
$(ii)$ Which solution has the lowest concentration of $H^{+}$ ions?

Why is $HCl$ a stronger acid than acetic acid?