Question detail

For Limiting reactants (HT only), which option best supports this Unit 4.3 objective: (HT only) Explain why one reactant may be used in excess to ensure another reactant is completely used?

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. To ensure that the other reactant is completely used
B. To increase the temperature of the reaction
C. To decrease the rate of the reaction
D. To change the color of the solution

Answer

The correct option is To ensure that the other reactant is completely used.

Explanation

The correct option is To ensure that the other reactant is completely used. To ensure that the other reactant is completely used is correct because it directly supports the approved learning objective to (HT only) Explain why one reactant may be used in excess to ensure another reactant is completely used. The reasoning belongs to Limiting reactants (HT only) within Use of amount of substance in relation to masses of pure substances, so it should not be confused with nearby quantitative ideas such as mass, moles, concentration, yield, atom economy, or gas volume unless those are named in the objective. Use the focus term HT only to keep the answer aligned with AQA GCSE Chemistry 8462 Unit 4.3. The other options are weaker because they either use the wrong formula, the wrong unit, a vague relationship, or the wrong quantitative context.

Common mistake

Excess Reactant Misunderstanding

Students often think that using an excess of one reactant will increase the amount of product formed, rather than ensuring that the limiting reactant is fully consumed.

Emphasize that the purpose of using an excess reactant is to ensure that the limiting reactant is completely used up, which allows for maximum product yield based on the limiting reactant. Keep the correction anchored to Limiting reactants (HT only); check formula, substitution, calculation, final answer, and unit where relevant.

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