${\mathrm{MgCl}}_2·{\mathrm{XH}}_2\mathrm{O},{\mathrm{CaCl}}_2·{\mathrm{YH}}_2\mathrm{O}$ and ${\mathrm{BaCl}}_2·{\mathrm{ZH}}_2\mathrm{O}$. The values of $\mathrm{X},\mathrm{V}$ and $\mathrm{Z}$ are respectively

Polarising Power $\propto \frac{1}{\text{ Stze of the cation }}$

Also, Polarising Power $\mathrm{\alpha }$ water of crystallization tendency

Size of cation order:

$${\mathrm{Ba}}^{2+}>{\mathrm{Ca}}^{2+}>{\mathrm{Mg}}^{2+}$$

Therefore, polarising power order:

$${\mathrm{Ba}}^{2+}<{\mathrm{Ca}}^{2+}<{\mathrm{Mg}}^{2+}$$

Thus, the tendency to form water of crystallization will be more for magnesium than calcium and then barium.

So, the given compounds are ${\mathrm{MgCl}}_2·8{\mathrm{H}}_2\mathrm{O},{\mathrm{CaCl}}_2·6{\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{BaCl}}_2·2{\mathrm{H}}_2\mathrm{O}$. $\Rightarrow \mathrm{X}=8,\mathrm{Y}=6$ and $\mathrm{Z}=2$.