Aqueous ammonia is used instead of aqueous Na | vedclass

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Question

(B) $Al^{3+}$ ions react with $NaOH$ to form $Al(OH)_3$ initially. However,$Al(OH)_3$ is amphoteric in nature and dissolves in excess $NaOH$ to form a

Vedclass · Accepted Answer

$NaOH$ forms $[Al(OH)_4]^-$ ions.

Vedclass · Answer

(B) $Al^{3+}$ ions react with $NaOH$ to form $Al(OH)_3$ initially. However,$Al(OH)_3$ is amphoteric in nature and dissolves in excess $NaOH$ to form a soluble complex,$[Al(OH)_4]^-$. To avoid the formation of this soluble complex and ensure complete precipitation of $Al(OH)_3$,a weaker base like aqueous ammonia $(NH_4OH)$ is used. $NH_4OH$ provides a lower concentration of $OH^-$ ions,which is sufficient to precipitate $Al(OH)_3$ but not enough to dissolve it.

Aqueous ammonia is used instead of aqueous $NaOH$ solution to precipitate $Al^{3+}$ ions as $Al(OH)_3$ because .................

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