Question

Copper(i) iodide is stable but copper(ii) iodide does not exist

Answer 1

Iodide ions are strong reducing agents. Therefore, Copper (II) Iodide reduces to insoluble copper (I) iodide. Thus making CuI2, CuI. CuI is not stable, so it doesn't exist in solution. It isn't stable because of electrochem and the solubility. 

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