What is the effect of adding gypsum to cement?

$CaCO_3$ was reacted with dil $HCl$ to form three products. One of the products formed,when passed into slaked lime,gave $X$. What is $X$?

$ZnO$ when heated with $BaO$ at $1100\,^{\circ}C$ gives a compound. Identify the compound.

Chemical $A$ is used for water softening to remove temporary hardness. $A$ reacts with $Na_2CO_3$ to generate caustic soda. When $CO_2$ is bubbled through $A$,it turns cloudy. What is the chemical formula of $A$?

Given below are two statements:
Statement $I$: None of the alkaline earth metal hydroxides dissolve in alkali.
Statement $II$: Solubility of alkaline earth metal hydroxides in water increases down the group.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following is the characteristic outer shell electronic configuration of alkaline earth metals?