WAEC Chemistry 2021 Objective — Question 18
Question 18 of 50 from the West African Examinations Council (WAEC) Chemistry 2021 Objective paper, with the correct answer and a full explanation.
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18. What would be observed when aqueous ammonia is added in drops and then in excess to a solution of copper (II) ions?
- A. A blue precipitate is formed which is soluble in excess ammoniaCorrect
- B. A brick red precipitate is produced which is insoluble in excess ammonia
- C. A white precipitate is formed which is soluble in excess ammonia
- D. A green precipitate is formed which is insoluble in excess ammonia
Explanation
Cu²⁺ ions form a pale blue precipitate of Cu(OH)2 with dilute ammonia, which dissolves in excess ammonia to form a deep blue soluble complex.
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