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  4. Assertion: Alkyl iodide can be prepared by treating alkyl chloride/bromide with Nal in acetone. Reason: NaCl/NaBr are soluble in acetone while Nal is not.

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Q. Assertion: Alkyl iodide can be prepared by treating alkyl chloride/bromide with Nal in acetone.
Reason: NaCl/NaBr are soluble in acetone while Nal is not.

AIIMSAIIMS 2007Haloalkanes and Haloarenes

Solution:

This is Finkelstein reaction which involves the conversion of an alkyl chloride/bromide to an alkyl iodide by the addition of sodium iodide in acetone. Because sodium iodide is soluble in acetone and $NaCl$ and $NaBr$ are not, the equilibrium is shifted by the precipitation of insoluble salt.
$R - X \xrightleftharpoons[MX]{MX'} R - X'$
The equilibrium position of the reaction depends on the nucleophilicity of the anion, whether a good leaving group is present and whether one anion is better stabilised than the other in a given solvent.