Explain the preparation of alkyl halides by halogen exchange methods.

(N/A) $(i)$ Finkelstein Reaction: Alkyl iodides are often prepared by the reaction of alkyl chlorides or alkyl bromides with $NaI$ in dry acetone.
$CH_3CH_2Br + NaI \xrightarrow{\text{Acetone}} CH_3CH_2I + NaBr$
$\text{Bromoethane} \rightarrow \text{Iodoethane}$
$CH_3CH_2Cl + NaI \xrightarrow{\text{Acetone}} CH_3CH_2I + NaCl$
$NaCl$ or $NaBr$ thus formed is precipitated in dry acetone. It facilitates the forward reaction according to Le Chatelier's Principle.
$(ii)$ Swarts Reaction: The synthesis of alkyl fluorides is best accomplished by heating an alkyl chloride or alkyl bromide in the presence of a metallic fluoride such as $AgF$,$Hg_2F_2$,$CoF_2$,or $SbF_3$.
$CH_3Br + AgF \rightarrow CH_3F + AgBr$