Question detail
What observation indicates the presence of copper(II) ions when sodium hydroxide is added?
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 precipitate forms
- C. A white precipitate forms
- D. No precipitate forms
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 link observations to conclusions in qualitative analysis. This reasoning is anchored to Aqueous ion tests (A-level only) in Reactions of ions in aqueous solution (A-level only), and it separates qualitative analysis 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
Misinterpreting Observations
Students often confuse the observations made during qualitative tests, such as mistaking a color change for a different ion than what was actually present.
To avoid this, clearly link each observation to its corresponding conclusion. For example, if a blue precipitate forms when sodium hydroxide is added to a copper(II) ion solution, conclude that copper(II) ions are present based on the specific color change observed.
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