Which of the alkali metals has the least melting point?

$NaOH$ (solid) $+ CO \xrightarrow{200^\circ C} X$; product $X$ is

Which of the following compounds has a positive enthalpy of solution?

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.

Important ore of $Mg$ is

Which of the following properties is $NOT$ an anomalous property of $Li$?