Question detail
Case 86 formula-choice. A student starts a worked solution. Which first step is most appropriate? Focus on that balanced chemical equation the total relative in Relative formula mass, not on a neighbouring Unit 4.3 idea.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations
Question
- A. Case 86 formula-choice: Use the named relationship before substituting numbers for that balanced chemical equation the total relative
- B. Case 86 formula-choice: Start with a memorised answer and add a unit later (Relative formula mass)
- C. Case 86 formula-choice: Change every number into a percentage before choosing a formula (that balanced chemical equation the total relative)
- D. Case 86 formula-choice: Use a nearby formula from a different quantitative chemistry subtopic (Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations)
Answer
The correct option is Case 86 formula-choice: Use the named relationship before substituting numbers for that balanced chemical equation the total relative.
Explanation
The correct option is Case 86 formula-choice: Use the named relationship before substituting numbers for that balanced chemical equation the total relative. It supports the approved learning objective by keeping the method tied to that balanced chemical equation the total relative in Relative formula mass. The other options are incorrect because they either use the wrong quantitative relationship, lose the required unit, confuse coefficients with subscripts, or report an answer without a complete worked method.
Common mistake
Misunderstanding Mass Conservation
Students often think that the mass of reactants and products can differ if gases are involved, not realizing that the total mass remains constant.
Emphasize that the law of conservation of mass states that no atoms are lost or gained, so the total mass of reactants must equal the total mass of products, regardless of the state of matter. Keep the correction anchored to Relative formula mass; check formula, substitution, calculation, final answer, and unit where relevant.
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