Question detail
Case 38 unit-check. A student checks the units in a calculation. Which decision keeps the method valid? Focus on Distinguish atom economy percentage yield when evaluating in Atom economy, 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
Yield and atom economy of chemical reactions (chemistry only)
Question
- A. Case 38 unit-check: Keep the required unit linked to the quantity being calculated for Distinguish atom economy percentage yield when evaluating
- B. Case 38 unit-check: Ignore the unit because the number is more important (Atom economy)
- C. Case 38 unit-check: Swap dm3 and cm3 without converting the value (Distinguish atom economy percentage yield when evaluating)
- D. Case 38 unit-check: Use grams, moles, and percentage signs interchangeably (Yield and atom economy of chemical reactions (chemistry only))
Answer
The correct option is Case 38 unit-check: Keep the required unit linked to the quantity being calculated for Distinguish atom economy percentage yield when evaluating.
Explanation
The correct option is Case 38 unit-check: Keep the required unit linked to the quantity being calculated for Distinguish atom economy percentage yield when evaluating. It supports the approved learning objective by keeping the method tied to Distinguish atom economy percentage yield when evaluating in Atom economy. 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 Atom Economy with Percentage Yield
Students often confuse atom economy with percentage yield, thinking they represent the same concept.
To fix this, remember that atom economy measures the efficiency of a reaction in terms of how much of the starting materials are converted into useful products, while percentage yield compares the actual product obtained to the theoretical maximum. Keep the correction anchored to Atom economy; check formula, substitution, calculation, final answer, and unit where relevant.
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