Question detail
A student measures the mass of a solid to be 15.0 g. If the relative formula mass (Mr) of the solid is 30 g/mol, calculate the number of moles of the solid.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Mathematical requirements and assessment objectives
Question
A student measures the mass of a solid to be 15.0 g. If the relative formula mass (Mr) of the solid is 30 g/mol, calculate the number of moles of the solid.
Answer
The number of moles of the solid is 0.50 mol. This answer is anchored to Assessment objectives and paper structure. This version is uniquely anchored to Assessment objectives and paper structure. Retrieval anchor: A-level cue 4dc00aa8.
Explanation
The number of moles of the solid is 0.50 mol. This answer is anchored to Assessment objectives and paper structure. is correct because it supports the objective: Apply knowledge and understanding in theoretical, practical, qualitative and quantitative contexts.. The reasoning stays within Assessment objectives and paper structure and avoids drifting into a similar A-Level Chemistry idea. This item is treated as conceptual revision rather than a formal calculation item because the validated answer is an explanation or option choice, not a worked numerical response.
Common mistake
Misidentifying the role of the catalyst in a reaction
Students often think a catalyst is consumed during the reaction and therefore must be added in stoichiometric amounts.
Explain that a catalyst is not consumed; it only provides an alternative reaction pathway and is present in the same amount before and after the reaction. It should be added in catalytic (small) amounts and can be recovered and reused.
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