A-LevelChemistryAtoms, molecules and stoichiometryOct/Nov 2022Paper 1 Q41 Mark

Calcium oxide and magnesium sulfide each react with acid. CaO(s) + 2H+(aq) → Ca²+(aq) + H2O(l) MgS(s) + 2H+(aq) → Mg2+(aq) + H2S(g) A mixture of these two compounds, X, reacts with exactly 0.125 mol of dilute hydrochloric acid. The amount of hydrogen sulfide formed is 0.0250 mol. What was the mass of calcium oxide in mixture X?

Q: What is the correct answer to this A-Level Chemistry question?

The correct answer is B: 2.1 g.

Q: What topic does this question test?

This question tests Atoms, molecules and stoichiometry in A-Level Chemistry (syllabus code 9701). It is worth 1 mark.

A1.4 g

B2.1 g

C2.8 g

D4.2 g

✓ Correct Answer

The correct answer is B: 2.1 g

📋 Examiner Report & Trap Analysis

Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...

🎯 Mark Scheme Breakdown

Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.

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About This A-Level Chemistry Question

Topic

This multiple-choice question tests Atoms, molecules and stoichiometry in A-Level Chemistry (syllabus code 9701). It is worth 1 mark.

Source

This question appeared in the Cambridge A-Level Chemistry Oct/Nov 2022 examination, Paper 1 Variant 2.

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