The reaction $$2 \mathrm{R}-\mathrm{Cl}+\mathrm{CoF}_2 \longrightarrow 2 \mathrm{R}-\mathrm{F}+\mathrm{CoCl}_2$$ is an example of ............... .

Which among the following methods is not suitable for the preparation of alkyl chlorides?

Identify the catalyst $$X$$ used in following reaction.

$$\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{Br}+2[\mathrm{H}] \xrightarrow{X} \mathrm{CH}_3-\mathrm{CH}_3+\mathrm{HBr}$$