The main salt soluble in sea water is

Metals dissolve in liquid ammonia giving coloured solutions which are conducting in nature. The colour of the solution and reason of its conductance is

Compound $A$ reacts with $NH_4Cl$ and forms a compound $B$. Compound $B$ reacts with $H_2O$ and excess of $CO_2$ to form compound $C$,which on reaction with saturated $NaCl$ solution forms sodium hydrogen carbonate. Compounds $A, B$ and $C$ are respectively:

When $CO$ is passed over solid $NaOH$ heated to $200\,^{\circ}C$,it forms

What is the gas produced in the reaction: $KO_2 + CO_2 \to ?$

Oxygen gas can be prepared from solid $KMnO_4$ by