Which of the following carbonates decomposes upon heating?

Which of the following is the weakest base among $NaOH$,$Ca(OH)_2$,$KOH$,and $Be(OH)_2$?

Assertion $(A):- MgSO_{4}$ is readily soluble in water.
Reason $(R):-$ The greater hydration enthalpy of $Mg^{2+}$ ions overcomes its lattice enthalpy.

$Mg(NO_3)_2 \cdot XH_2O$ and $Ba(NO_3)_2 \cdot YH_2O$ represent the formulas of the crystalline forms of nitrate salts. The sum of $X$ and $Y$ is $.........$.

Which one of the following alkaline earth metal sulphates has its hydration enthalpy greater than its lattice enthalpy?

The incorrect order of solubility in water is