JEE Advanced2006ChemistryPractical ChemistryActual
A solution when diluted with H ₂ O and boiled, it gives a white precipitate. On addition of excess NH ₄ Cl / NH ₄ OH , the volume of precipitate decreases leaving behind a white gelatinous precipitate. Identify the precipitate which dissolves in NH ₄ OH / NH ₄ Cl .
Options
- AZn ( OH )₂
- BAl ( OH )₃
- CMg ( OH )₂
- DCa ( OH )₂
Correct answer
A. Zn ( OH )₂
Step-by-step solution
A solution of Zn ²⁺ ion reacts with water which on boiling give white ppt. of Zn ( OH )₂ . This precipitates dissolve in excess of NH ₄ OH in presence of NH ₄ Cl because Zn ( OH )₂ on reaction with NH ₄ OH in presence of NH ₄ Cl forms tetrammine zinc (II) complex (soluble).