Question detail
What is the observation when dilute hydrochloric acid is added to a sample containing carbonate ions?
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 gas is produced that turns limewater milky
- B. A white precipitate forms
- C. The solution turns blue
- D. No visible change occurs
Answer
A gas is produced that turns limewater milky
Explanation
The correct option is A gas is produced that turns limewater milky. A gas is produced that turns limewater milky is the best answer because it directly supports the AQA A-Level Chemistry objective to identify carbonate, sulfate and halide ions using appropriate tests. This reasoning is anchored to Aqueous ion tests (A-level only) in Reactions of ions in aqueous solution (A-level only), and it separates carbonate 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 Halide Ions
Students often confuse the tests for halide ions, mistakenly using silver nitrate for sulfates instead of halides.
To correctly identify halide ions, use the test with silver nitrate. The reaction is: AgNO3 + NaCl → AgCl (white precipitate). Ensure to remember that barium chloride is used for sulfate tests.
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