Which of the following is dolomite?

Give a brief explanation of the ionisation enthalpy of alkaline earth metals (Group-$2$) elements.

Choose the correct statement$(s)$:
$A.$ Beryllium oxide is purely acidic in nature.
$B.$ Beryllium carbonate is kept in the atmosphere of $CO_2$.
$C.$ Beryllium sulphate is readily soluble in water.
$D.$ Beryllium shows anomalous behavior.
Choose the correct answer from the options given below:

The halides of alkaline earth metals form hydrates such as $MgCl_2 \cdot 6H_2O$,$CaCl_2 \cdot 6H_2O$,$BaCl_2 \cdot 2H_2O$,and $SrCl_2 \cdot 2H_2O$. What does this indicate about the halides of group $2$ elements?

When $CO_2$ is passed into lime water,it turns milky. When an excess of $CO_2$ is passed,the milkiness disappears because:

What is the purpose of adding gypsum $(CaSO_4 \cdot 2H_2O)$ to cement?