Potassium nitrate is called

Carnallite is a mineral of

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R:$
Assertion $A:$ Metallic sodium dissolves in liquid ammonia giving a deep blue solution,which is paramagnetic.
Reason $R:$ The deep blue solution is due to the formation of amide.
In the light of the above statements,choose the correct answer from the options given below:

(Milky Cloud) $C \xleftarrow{CO_2} A + Na_2CO_3 \rightarrow B + C$
The chemical formulae of $A$ and $B$ are

Which of the following alkali metals reacts directly with nitrogen?

Magnesium wire is heated in the atmosphere of $CO_2$ because