NTA Abhyas NEET2020Chemistryp Block Elements (Group 13 & 14)Practice
Aqueous ammonia is used as a precipitating reagent for Al 3 + ions as Al(OH) 3 rather than aqueous NaOH, because
Options
- ANH 4 + is a weak base
- BNaOH is a very strong base
- CNaOH forms [Al(OH) 4 ] − ions
- DNaOH forms [Al(OH) 2 ] + ions.
Correct answer
C. NaOH forms [Al(OH) 4 ] − ions
Step-by-step solution
Al(OH) 3 formed with NaOH dissolves in excess of NaOH to form aluminate ion. which is stable. AlCl 3 + 3 NaOH ⟶ 2 Al OH 3 ↓ + 3 NaCl Al OH 3 + OH − → Al OH 4 − Soluble