Question detail

Chemical changes case 029 salt-method. A student plans a salt preparation method. Which option is most creditworthy? Focus on the test for carbon dioxide limewater in Neutralisation of acids and salt production, not on a neighbouring Unit 4.4 reaction idea.

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

Reactions of acids

Question

A. Chemical changes case 029 salt-method: Uses the correct reactants, separation step and crystallisation idea for the test for carbon dioxide limewater
B. Chemical changes case 029 salt-method: Evaporates to dryness when crystals should be formed carefully (Neutralisation of acids and salt production)
C. Chemical changes case 029 salt-method: Adds indicator to every salt preparation regardless of method (the test for carbon dioxide limewater)
D. Chemical changes case 029 salt-method: Names a salt but omits how excess solid or solution is handled (Reactions of acids)

Answer

The correct option is Chemical changes case 029 salt-method: Uses the correct reactants, separation step and crystallisation idea for the test for carbon dioxide limewater.

Explanation

The correct option is Chemical changes case 029 salt-method: Uses the correct reactants, separation step and crystallisation idea for the test for carbon dioxide limewater. It is correct because it directly supports the approved learning objective to describe the test for carbon dioxide using limewater in Neutralisation of acids and salt production. The other options are incorrect because they blur a Unit 4.4 concept boundary: acid versus alkali versus base, oxidation versus reduction, displacement versus reduction, electrolysis versus electroplating, anode versus cathode, positive versus negative ions, oxidation state versus ionic charge, or strong acid versus concentrated acid.

Common mistake

Common Mistake in Testing for Carbon Dioxide

Students often confuse the test for carbon dioxide with the test for hydrogen gas, thinking that a lighted splint is used for both tests.

Remember that the test for carbon dioxide involves bubbling the gas through limewater, which turns milky, while the test for hydrogen gas uses a lighted splint that produces a 'pop' sound.

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