Which of the following salts increases the rate of the setting process of Plaster of Paris?

$A$ metal $M$ readily forms a water-soluble sulphate and a water-insoluble hydroxide $M(OH)_2$. Its oxide $MO$ is amphoteric,hard,and has a high melting point. The alkaline earth metal $M$ must be

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

Which of the following is an amphoteric hydroxide?

Assertion : Of the various chlorides of alkaline earth metals $BeCl_2$ is covalent in nature,whereas $MgCl_2$ and $CaCl_2$ are ionic compounds.
Reason : $Be$ is the first member of group $2$.

Among the following,which is water insoluble?