Question detail

Case 84 formula-choice. A student starts a worked solution. Which first step is most appropriate? Focus on the limiting reactant the reactant that completely 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 84 formula-choice: Use the named relationship before substituting numbers for the limiting reactant the reactant that completely
B. Case 84 formula-choice: Start with a memorised answer and add a unit later (Limiting reactants (HT only))
C. Case 84 formula-choice: Change every number into a percentage before choosing a formula (the limiting reactant the reactant that completely)
D. Case 84 formula-choice: Use a nearby formula from a different quantitative chemistry subtopic (Use of amount of substance in relation to masses of pure substances)

Answer

The correct option is Case 84 formula-choice: Use the named relationship before substituting numbers for the limiting reactant the reactant that completely.

Explanation

The correct option is Case 84 formula-choice: Use the named relationship before substituting numbers for the limiting reactant the reactant that completely. It supports the approved learning objective by keeping the method tied to the limiting reactant the reactant that completely 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 Reactant

Students often confuse the limiting reactant with the reactant present in excess, thinking both are the same.

Remember that the limiting reactant is the one that gets completely used up, while the excess reactant remains after the reaction.

Related flashcards

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For Limiting reactants (HT only), which option best supports this Unit 4.3 objective: (HT only) Define the limiting reactant as the reactant that is completely used up in a reaction?