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JAMB Chemistry 1991 Question 36

Question 36

Metals and their Compounds

Addition of aqueous ammonia to a solution of Zn2+ gives a white precipitate which dissolves in an excess of ammonia because

  1. A.zinc is amphoteric
  2. B.zinc hydroxide is readily soluble
  3. C.zinc forms a complex which is readily soluble in excess ammonia
  4. D.ammonia solution is a strong base.
Show the answer and explanation

Answer: C (zinc forms a complex which is readily soluble in excess ammonia)

Explanation

Zn(OH)2 reacts with excess ammonia to form the soluble complex ion [Zn(NH3)4]2+.