Which of the following statements are correct?

AThe hydration enthalpy of $Mg X^{2 +}$ is larger in magnitude than that of $Ca X^{2 +}$ .
BBarium nitrate gives $BaO$ , $NO X_{2}$ and $O X_{2}$ on strong heating.
C $BeO$ is amphoteric.
D $Ca (HCO X_{3}) X_{2}$ exists as a stable solid at room temperature.

Answer: A, B, C

Mg X^{2 +}

is smaller than

Ca X^{2 +}

, so its hydration enthalpy is greater in magnitude.

BeO

dissolves in both acids and bases. Group 2 nitrates decompose as

2 Ba (NO X_{3}) X_{2} 2 BaO + 4 NO X_{2} + O X_{2}

. The hydrogencarbonates of group 2 exist only in solution, so the last statement is wrong.