Plaster of Paris is

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

Among the following,which is water insoluble?

Choose the correct statement from the following:
$(i)$ Beryllium is not readily attacked by acids because of the presence of an oxide film on the surface of the metal.
$(ii)$ $BeO$ is an amphoteric oxide.
$(iii)$ Beryllium exhibits coordination number more than four.
$(iv)$ Beryllium oxide is purely acidic in nature.

What is the substance known as 'blanc fixe' used in paints?

Assertion : Both $Be$ and $Al$ can form complexes such as $BeF_4^{2-}$ and $AlF_6^{3-}$ respectively,$BeF_6^{3-}$ is not formed.
Reason : In case of $Be$,no vacant $d-$ orbitals are present in its outermost shell.