The thermal stability of alkaline earth metal carbonates $MgCO_3$,$CaCO_3$,$BaCO_3$,and $SrCO_3$ decreases as:

$Y$ $\xleftarrow{\Delta ,\, 205^\circ C}$ $CaSO_4 \cdot 2H_2O$ $\xrightarrow{\Delta ,\, 120^\circ C}$ $X$. $X$ and $Y$ are respectively

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$ :
Assertion $(A)$ : $BeCl_2$ and $MgCl_2$ produce characteristic flame.
Reason $(R)$ : The excitation energy is high in $BeCl_2$ and $MgCl_2$.
In the light of the above statements,choose the correct answer from the option given below :

Identify correct statements from the following:
$i$. Beryllium oxide is an amphoteric oxide.
$ii$. Group $II$ elements dissolve in liquid ammonia to form deep blue-black solutions.
$iii$. The hydration enthalpy of group $II$ ions decreases from $Be^{2+}$ to $Ba^{2+}$.

Which of the following statements is false?

Give the composition of Portland cement.