Which among the following alkali metal chlorides crystallises in the form of a hydrate?

The metal that forms nitride by reacting directly with $N_2$ of air is

The correct order of electropositive nature of $Li$,$Na$ and $K$ is

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $LiF$ is sparingly soluble in water.
Reason $R$: The ionic radius of $Li^{+}$ ion is smallest among its group members,hence it has the least hydration enthalpy.
In the light of the above statements,choose the most appropriate answer from the options given below.

When sodium is heated with moist air,the product obtained is:

Which oxide does not give a pink color with phenolphthalein in an aqueous solution?