Which colour is developed in the solution when alkaline earth metals are dissolved in liquid ammonia?

Which of the following fluorides has the lowest melting point?

Give the name of group-$2$ elements.

Deep pink colour is given to flame by the salts of

Which of the following statement$(s)$ is/are correct?
$(i)$ $LiNO_3$ and $Ba(NO_3)_2$ both will give $NO_2$ on heating.
$(ii)$ $BaSO_4$ is less soluble in water than $CaSO_4$.
$(iii)$ Alkaline earth metals do not dissolve in liquid ammonia.

The reason for adding gypsum to the clinker during the production of cement is .........