Aqueous ammonia is used as a precipitating reagent for Al^ 3+ ions as Al(OH)_3 rather than aqueous NaOH, because:

JEE Main Chemistry question

Aqueous ammonia is used as a precipitating reagent for ions as rather than aqueous NaOH, because:

(A) is a weak base
(B)NaOH is a very strong base
(C)NaOH forms ionsCorrect
(D)NaOH forms ions

Answer: (C)

Solution

is amphoteric and redissolves in excess strong alkali (NaOH) to give the soluble aluminate ion, , which would cause loss of the precipitate; the weaker base

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Question ID VK-138650