Identify '$$\mathrm{A}$$' in the following reaction.

$$A \stackrel{\text { Na/dry ether }}{\longrightarrow}$$ 3,4-diethyl-3,4-dimethylhexane $$+2 \mathrm{NaCl}$$

For the reaction $$2 \mathrm{NO}+\mathrm{Cl}_2 \rightarrow 2 \mathrm{NOCl}$$

What is the relation between $$\frac{\mathrm{d}[\mathrm{NO}]}{\mathrm{dt}}$$ and $$\frac{\mathrm{d}[\mathrm{NOCl}]}{\mathrm{dt}}$$ ?

What type of hybridization is exhibited by [CoF$$_6$$]$$^{3-}$$ ?

Which among the following is NOT the use of SO$$_2$$ gas?