Question detail
What is the observation when testing for carbonate ions using dilute acid?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
AS practical skills and required practical activities
Question
- A. Effervescence is observed.
- B. A white precipitate forms.
- C. The solution turns blue.
- D. No visible change occurs.
Answer
Effervescence is observed.
Explanation
The correct option is Effervescence is observed.. Effervescence is observed. is the best answer because it directly supports the AQA A-Level Chemistry objective to required practical 4: identify required cations and anions using test-tube reactions. This reasoning is anchored to AS required practical activities in AS practical skills and required practical activities, and it separates required practical 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
Identifying Cations Incorrectly
Students often confuse the tests for different cations, leading to incorrect identification.
To correctly identify cations, remember the specific reagents and expected precipitate colors. For example, when adding sodium hydroxide to a solution containing copper(II) ions, the expected observation is a blue precipitate of copper(II) hydroxide. Use the formula: cation test = reagent + solution -> observation. Substitute with the correct cation and reagent to ensure accurate results.
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