Which of the following alkali metals has a density greater than water?

Which process is associated with the production of sodium carbonate?

$A$ certain metal $M$ is used to prepare an antacid,which is used as a medicine for acidity. This metal accidentally catches fire,which cannot be extinguished by using $CO_2$ based extinguishers. The metal $M$ is

$Al$ utensils should not be cleaned with materials containing washing soda because .............

All compounds of alkali metals are easily soluble in water,but lithium compounds are more soluble in organic solvents. Explain.

Assertion $A$: Alkali metal elements impart characteristic colors to the flame in a flame test.
Reason $R$: They have very low ionization enthalpy.