Question

which of the following ion does not produce soluble complex in excess of NaOH solution

1)Cr+3
2)Zn+2
3)Al+3
4)Fe+3

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Answer 1

ANSWER:-

The answer is 3)Al+3.

➡️Copper and various other transition metals in solution tend to form insoluble hydroxides. This tendency has been used for removing such metals from industrial wastewaters.

➡️Zn 2+ would produce a soluble complex,

If excess sodium hydroxide is added, the precipitate of zinc hydroxide will dissolve, forming a colorless solution of zincate ion: Zn(OH)2 + 2OH- → Zn(OH)42-. This property can be used as a test for zinc ions in solution, but it is not exclusive, since aluminum and lead compounds behave in a very similar manner. Unlike the hydroxides of aluminum and lead, zinc hydroxide also dissolves in aqueous ammonia to form a colourless, water-soluble amine complex.

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