Question detail

Case 57 answer-sense. A student reviews the final answer. Which check best catches an exam error? Focus on limiting reactants terms masses grams in Limiting reactants (HT only), not on a neighbouring Unit 4.3 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

Use of amount of substance in relation to masses of pure substances

Question

A. Case 57 answer-sense: Check that the answer size, unit, and chemical context all match for limiting reactants terms masses grams
B. Case 57 answer-sense: Accept the answer if it has many decimal places (Limiting reactants (HT only))
C. Case 57 answer-sense: Choose the answer with the biggest number because it looks more complete (limiting reactants terms masses grams)
D. Case 57 answer-sense: Drop the unit if the working contains a formula (Use of amount of substance in relation to masses of pure substances)

Answer

The correct option is Case 57 answer-sense: Check that the answer size, unit, and chemical context all match for limiting reactants terms masses grams.

Explanation

The correct option is Case 57 answer-sense: Check that the answer size, unit, and chemical context all match for limiting reactants terms masses grams. It supports the approved learning objective by keeping the method tied to limiting reactants terms masses grams in Limiting reactants (HT only). 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

Confusing Limiting Reactants with Excess Reactants

Students often think that the limiting reactant is the one that is present in the smallest mass, rather than understanding that it is the reactant that is completely used up in the reaction.

To fix this, students should focus on the definition of a limiting reactant as the one that runs out first, regardless of its mass compared to other reactants.

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Case 58 exam-language. Which response would earn credit for the calculation method? Focus on limiting reactants terms masses grams in Limiting reactants (HT only), not on a neighbouring Unit 4.3 idea.