The property of the alkaline earth metals that increases with their atomic number is

The correct sequence of increasing melting points of $BeCl_2$,$MgCl_2$,$CaCl_2$,$SrCl_2$,and $BaCl_2$ is:

What are $X$,$Y$ and $Z$ in the following reactions?
$CaCO_3 \stackrel{\Delta}{\rightleftharpoons} CO_2 + X$
$X + H_2O \longrightarrow Y$
$Y + Cl_2 \longrightarrow Z$

How would you explain the following observations?
$(i)$ $BeO$ is almost insoluble but $BeSO_4$ is soluble in water,
$(ii)$ $BaO$ is soluble but $BaSO_4$ is insoluble in water,
$(iii)$ $LiI$ is more soluble than $KI$ in ethanol.

The alkaline earth metal sulphate, which has its hydration enthalpy greater than its lattice energy is

Which of the following represents the correct order of solubility in water?