Question

Aqueous ammonia is used as a precipitating reagent for Al³⁺ ions as Al(OH)₃ rather than aqueous NaOH, because

• A. ${\text{NH}}_4^{+}$ is a weak base
• B. $\text{NaOH}$ is a very strong base
• C. $NaOH$ forms $[Al(OH{)}_4{]}^{-}$ ions
• D. $\text{NaOH}$ forms ${\left[\mathrm{Al}(\mathrm{OH}{)}_2\right]}^{+}$ ions.

Answer 1

Answer: (C)

Al(OH)₃ formed with NaOH dissolves in excess of NaOH to form aluminate ion.

which is stable.