Question detail
What is the observation when copper(II) ions react with ammonia?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Reactions of ions in aqueous solution (A-level only)
Question
- A. A blue precipitate forms
- B. A green solution forms
- C. A white precipitate forms
- D. No visible change occurs
Answer
A blue precipitate forms
Explanation
The correct option is A blue precipitate forms. A blue precipitate forms is the best answer because it directly supports the AQA A-Level Chemistry objective to describe reactions of aqueous metal ions with ammonia. This reasoning is anchored to Aqueous ion tests (A-level only) in Reactions of ions in aqueous solution (A-level only), and it separates ammonia from similar A-Level ideas rather than relying on a vague recall statement. Other options are weaker if they use the wrong evidence, calculation, mechanism, observation, unit, or conclusion for this subtopic.
Common mistake
Misidentifying Precipitate Colors
Students often incorrectly identify the colors of precipitates formed when aqueous metal ions react with ammonia, confusing them with those formed with sodium hydroxide.
To accurately describe the reactions, remember the specific colors associated with each metal ion when reacting with ammonia. For example, copper(II) ions produce a blue precipitate of copper(II) hydroxide with sodium hydroxide, but with ammonia, they form a deep blue solution of tetraamminecopper(II) complex. Always refer to reliable sources or color charts for correct identification.
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