# Confusion regarding Finkelstein Reaction [duplicate]

In Finkelstein reaction we know when a primary alkyl chloride or bromide is treated with NaI in acetone, we get the corresponding alkyl iodide Now acetone is a polar aprotic solvent and order of nucleophilicity in acetone is F->Cl->Br->I-. I have read some articles on chemistry.stackexchange which explain why the driving force behind Finkelstein reaction is the precipitation of NaCl or NaBr. But one thing I am still not able to get why the Carbon chlorine or Carbon Bromine bond breaks in the first place by a relatively weaker nucleophile ie I-.

First, $$\ce{NaI}$$ is soluble in acetone while $$\ce{NaBr}$$ and $$\ce{NaCl}$$ are not. Here, the reaction is $$\ce{S_N2}$$ so the nucleophile, $$\ce{I-}$$, will displace the other halide. The other leaving group halide will enter the solution as $$\ce{NaBr}$$ or $$\ce{NaCl}$$ which will precipitate. It doesn't matter if $$\ce{Cl-}$$ or $$\ce{I-}$$ is a stronger nucleophile in acetone since they are the leaving group and won't be present in the solution once they are precipitated.