Aqueous copper(II) sulfate is treated with excess KI: 2Cu^2+ + 4I^- -> 2CuI + I2. The precipitate and the magnetic nature of copper in it are:

blue CuI; paramagnetic with 1 unpaired electron

white CuI; paramagnetic with 1 unpaired electron

JEE Advanced levelSingle correct optionDifficulty 3 of 3df155

Aqueous copper(II) sulfate is treated with excess $KI$ : $2 Cu X^{2 +} + 4 I X^{-} 2 CuI + I X_{2}$ . The precipitate and the magnetic nature of copper in it are:

The equation balances (charge 0 on both sides). Cu(II) is reduced to Cu(I),

3 d^{10}

, so

CuI

has no unpaired electron and no d-d transition, and it is a white solid. The brown colour belongs to the iodine formed.