Question detail
Calculate the atom economy for the reaction: 2C2H4 + 5O2 → 4CO2 + 4H2O. What is the atom economy?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Amount of substance
Question
- A. 100%
- B. 75%
- C. 50%
- D. 25%
Answer
75%
Explanation
Using the formula: atom economy = (Mr of desired product / sum of Mr of all products) x 100. The Mr of CO2 is 44 and H2O is 18. The total Mr of reactants (2C2H4 + 5O2) is 2(28) + 160 = 216. Substituting gives: (4 * 44 + 4 * 18) / 216 x 100 = 75%.
Common mistake
Common Mistake in Atom Economy Calculation
Students often confuse atom economy with percentage yield, calculating it incorrectly by using actual yield instead of the relative formula mass of the desired product.
To calculate atom economy, use the formula: atom economy = (Mr of desired product / sum of Mr of all products) x 100. For example, if the desired product has a relative formula mass (Mr) of 18 g/mol and the total products have a sum of 36 g/mol, substitute: atom economy = (18 / 36) x 100 = 50%. Therefore, the atom economy is 50%.
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