Two alkali halide salts,$ACl$ and $BCl$,gave crimson red and violet colors in their flame tests,respectively. $A$ and $B$ are respectively:

What is the chemical formula of washing soda?

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:

Assertion : $K$,$Rb$ and $Cs$ (all belonging to group $1$) can also form superoxides.
Reason : The ionic radii of $K$,$Rb$ and $Cs$ show the following trend $Cs^{+} < Rb^{+} < K^{+}$.

What is the correct order of stability for the superoxides?

Which of the following statements is not true for most of the alkali metals?