JEE Main2018Chemistryd and f Block ElementsActual
The incorrect statement is:
Options
- ACu 2 + ion gives chocolate coloured precipitate with potassium ferrocyanide solution
- BCu 2 +   and   Ni 2 + ions give black precipitate with H 2 S in presence of HCl solution
- CFerric ion gives blood red colour with potassium thiocyanate
- DCu 2 + salts give red coloured borax bead test in reducing flame
Correct answer
B. Cu 2 +   and   Ni 2 + ions give black precipitate with H 2 S in presence of HCl solution
Step-by-step solution
Cu +2 gives black precipitate in presence of dil. HCl Ni +2 ions gives black precipitate in presence of NH 4 Cl +NH 3 with HCl S 2- concentration is not just sufficient to overcome the solubility product of NiS. Cu + 2 + H 2 S → dil .   HCl Cu 2 S ↓ ( black ) + 2 H + Ni + 2 + H 2 S → NH 4 Cl NH 4 OH NiS ↓ ( black ) + 2 H +