The blue color of a solution of sodium in liquid ammonia is due to the presence of.....

Consider the following statements.
$I$. $Cs^{+}$ ion is more highly hydrated than other alkali metal ions.
$II$. Among the alkali metals,only lithium forms a stable nitride by direct combination with nitrogen.
$III$. Among the alkali metals $Li, Na, K, Rb$,the metal $Rb$ has the highest melting point.
$IV$. Among the alkali metals $Li, Na, K, Rb$,only $Li$ forms peroxide when heated with oxygen.
Select the correct statement.

What are the metal ions present in carnallite?

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The alkali metals and their salts impart characteristic colour to reducing flame.
Reason $R$: Alkali metals can be detected using flame tests.
In the light of the above statements,choose the most appropriate answer from the options given below.

Which of the following alkali metals reacts directly with nitrogen?

On heating 'Trona $(Na_2CO_3 \cdot NaHCO_3 \cdot 2H_2O)$' with the help of a Bunsen burner,we get . . . . . . as the solid residue.