Which of the following ions has the largest heat of hydration?

Match the following:

List-$I$	List-$II$
$I$. $CaSO_4 \cdot 2H_2O$	$A$. Knee cement
$II$. $CaSO_4 \cdot 0.5H_2O$	$B$. Gypsum
$III$. $CaSO_4$	$C$. Plaster of Paris
	$D$. Dead burnt plaster

Match Column $(A)$ with the appropriate options in Column $(B)$.

Column $(A)$	Column $(B)$
$(a)$ $BeO$	$(p)$ Amphoteric
$(b)$ $MgCO_3 \cdot CaCO_3$	$(q)$ Dolomite
$(c)$ $BeCl_2$	$(r)$ Covalent
$(d)$ $Al(OH)_3$	$(s)$ Basic

When water is added to compound $(A)$ of calcium,a solution of compound $(B)$ is formed. When carbon dioxide is passed into the solution,it turns milky due to the formation of compound $(C)$. If excess of carbon dioxide is passed into the solution,the milkiness disappears due to the formation of compound $(D)$. Identify the compounds $A$,$B$,$C$,and $D$. Explain why the milkiness disappears in the last step.

The solubilities of carbonates decrease down the magnesium group (Group $2$) due to a decrease in:

Which of the following alkaline earth metals is the most electropositive?