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The incorrect statement out of the following is - [JEE-Main On line-2018]

1. Cu2+ ion gives chocolate coloured precipitate with potassium ferrocyanide solution
2. Cu2+ and Ni2+ ions give black precipitate with H2S in presence of HCl solution
3. Ferric ion gives blood red colour with potassium thiocyanate
4. Cu2+ salts give red coloured borax bead test in reducing flame

Correct answer: Cu2+ and Ni2+ ions give black precipitate with H2S in presence of HCl solution

Solution

With H2S in presence of HCl, only group-II cations like Cu2+ precipitate (black CuS). Ni2+ needs an ammoniacal/basic medium (group IV) and does not give a precipitate in acidic solution, so the statement that both Cu2+ and Ni2+ give a black precipitate with H2S in HCl is incorrect.

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