Among the following,which is water insoluble?

The compound$(s)$ of alkaline earth metals,which are amphoteric in nature is/are

Gypsum is added to clinker during cement manufacture to:

The correct order of melting point for alkaline earth metals is:

Which of the following orders is correct $:-$

Chemical $A$ is used for the removal of temporary hardness of water. Compound $A$ reacts with $Na_2CO_3$ to produce caustic soda. When $CO_2$ gas is passed through $A$,it turns milky. What is the chemical formula of $A$?