Identify the use of mixture of $$\mathrm{Ar}$$ and $$\mathrm{N}_2$$ from following.

Which of the following is an alkali metal?

During the electrolysis of fused $$\mathrm{NaCl}$$, the product obtained at anode is

Identify product B in following reaction.

Propanone $$\xrightarrow{\mathrm{Ba}(\mathrm{OH})_2} \mathrm{~A} \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\Delta} \mathrm{B}$$