Question detail

In a test for carbonate ions, what is the expected observation when dilute acid is added?

Try the question, check the answer, then read the explanation to understand the curriculum point.

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At a glance

MCQ

Type

practice

Style

Topic

A-level practical endorsement and required practical activities

Question

A. Effervescence due to carbon dioxide gas
B. A color change to blue
C. A white precipitate forms
D. No observable change

Answer

Effervescence due to carbon dioxide gas

Explanation

The correct option is Effervescence due to carbon dioxide gas. Effervescence due to carbon dioxide gas 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 A-level required practical activities in A-level practical endorsement 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 Ions in Test-Tube Reactions

Students often confuse the tests for cations and anions, leading to incorrect identification of ions.

To correctly identify ions, remember the specific tests for each ion type. For example, use sodium hydroxide to test for cations: add a few drops of NaOH to the solution and observe the color of any precipitate formed. For anions, add dilute acid followed by barium chloride for sulfates or silver nitrate for halides, and note the resulting precipitate color. This systematic approach will help ensure accurate identification. Keep the correction anchored to A-level required practical activities and the objective: Required practical 4: identify required cations and anions using test-tube reactions.

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