FRQ — Matter - Its Nature and Behaviour

Case study·Challenge (5/5)·No calculator

Difficulty guide

The label describes the problem, not your ability.

1/5 - Foundational

Warm-up setup; checks one basic idea.

2/5 - Routine exam skill

Normal syllabus skill; usually one main rule or interpretation.

3/5 - Standard multi-step

Exam-style problem with multiple steps or a common trap.

4/5 - Hard exam skill

High-end exam problem; combines methods carefully.

5/5 - Challenge

Stretch problem beyond normal exam pressure.

Question

A compound of elements

X

and oxygen is prepared twice. In sample I,

2.8\,\text{g}

X

combines with

1.6\,\text{g}

oxygen. In sample II,

7.0\,\text{g}

X

combines with

4.0\,\text{g}

oxygen. A third sample contains

5.6\,\text{g}

X

Total: 5 marks

(a) Show whether samples I and II obey the law of constant proportion. (2 marks)

(b) Predict the mass of oxygen that should combine with $5.6\,\text{g}$ of $X$ . (2 marks)

Your response (optional — you can also work on paper)

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