Questions about Theoretical Yield and Percent Yield
Multiple-Choice Questions – Theoretical Yield and Percent Yield
1. What is the theoretical yield?
A) The actual amount of product obtained
B) The maximum amount of product possible
C) The amount of excess reactant
D) The mass of limiting reactant
E) The yield in a decomposition reaction
2. Percent yield is calculated as:
A) (Limiting Reactant / Actual Yield) × 100
B) (Actual Yield / Limiting Reactant) × 100
C) (Theoretical Yield / Actual Yield) × 100
D) (Actual Yield / Theoretical Yield) × 100
E) (Excess Reactant / Product Formed) × 100
3. If a reaction has a theoretical yield of 50 g and an actual yield of 40 g, what is the percent yield?
A) 70%
B) 75%
C) 80%
D) 85%
E) 90%
4. In a lab, 25 g of product was obtained. If the theoretical yield was 30 g, what is the percent yield?
A) 83.3%
B) 86.6%
C) 90.0%
D) 92.5%
E) 75.0%
5. A student performs a reaction with a theoretical yield of 120 g and collects 96 g. Percent yield?
A) 60%
B) 75%
C) 80%
D) 85%
E) 90%
6. If the percent yield is 100%, it means:
A) Some reactants were wasted
B) No product was formed
C) The actual and theoretical yields are equal
D) The actual yield is zero
E) There is limiting reactant remaining
7. What is the theoretical yield if 2 mol of A (molar mass = 50 g/mol) produces 1 mol of B (molar mass = 100 g/mol)?
A) 25 g
B) 50 g
C) 75 g
D) 100 g
E) 200 g
8. If 5 g of product is obtained, but the theoretical yield was 10 g, what is the percent yield?
A) 25%
B) 50%
C) 75%
D) 90%
E) 100%
9. Why is percent yield usually less than 100%?
A) Side reactions
B) Product loss during handling
C) Impurities
D) Incomplete reactions
E) All of the above
10. A chemical reaction has a 90% yield. If the theoretical yield is 200 g, what is the actual yield?
A) 180 g
B) 190 g
C) 195 g
D) 200 g
E) 210 g
11. Which factor does not affect percent yield?
A) Side reactions
B) Temperature
C) Molar mass
D) Purity of reactants
E) Reaction conditions
12. Theoretical yield depends on:
A) The excess reactant
B) Experimental errors
C) The limiting reactant
D) Percent yield
E) Actual yield
13. Actual yield is determined by:
A) Stoichiometry
B) The limiting reactant only
C) Mass–mass calculations
D) Measuring the product formed
E) Theoretical yield
14. A reaction has a theoretical yield of 70 g, but only 49 g is recovered. Percent yield?
A) 60%
B) 65%
C) 70%
D) 75%
E) 80%
15. A reaction has 40% yield. If 10 g of product is desired, how much should the theoretical yield be?
A) 25 g
B) 20 g
C) 15 g
D) 10 g
E) 5 g
16. If a reaction yields more than the theoretical yield, it is likely due to:
A) Accurate experiment
B) High purity reactants
C) Contaminated product
D) Perfect limiting reactant
E) Exact measurement
17. If the actual yield is greater than theoretical yield, what might have happened?
A) Product is pure
B) Mass measurement error
C) Reaction ran to completion
D) Limiting reactant was fully used
E) Theoretical yield was too high
18. A 50 g actual yield with a percent yield of 50% gives what theoretical yield?
A) 10 g
B) 25 g
C) 50 g
D) 75 g
E) 100 g
19. Which of the following best describes percent yield?
A) The amount of reactant in excess
B) The total mass of all products
C) A comparison of actual and possible product
D) The quantity of unreacted material
E) The mole ratio between products
20. A chemical reaction has a theoretical yield of 150 g and a percent yield of 60%. What is the actual yield?
A) 75 g
B) 80 g
C) 85 g
D) 90 g
E) 95 g
- Questions on Volume-Volume Stoichiometry
- Questions on Mass-Volume Stoichiometry
- Questions on Limiting Reactant
Answers and Explanations
1. B – Theoretical yield is the maximum amount of product that can be formed from a given amount of reactants.
2. D – Percent yield = (Actual Yield / Theoretical Yield) × 100.
3. C – (40 / 50) × 100 = 80%.
4. A – (25 / 30) × 100 = 83.3%.
5. C – (96 / 120) × 100 = 80%.
6. C – If percent yield is 100%, actual = theoretical yield.
7. D – 1 mol of B × 100 g/mol = 100 g.
8. B – (5 / 10) × 100 = 50%.
9. E – All listed reasons can lower percent yield.
10. A – 90% of 200 g = 180 g.
11. C – Molar mass affects calculations, but not yield percentage directly.
12. C – Theoretical yield is based on the limiting reactant.
13. D – Actual yield is what you measure in the lab.
14. D – (49 / 70) × 100 = 70%.
15. B – 40% of what = 10 g → x = 25 g → 25 g.
16. C – Yields over 100% are usually due to impurities or contamination.
17. B – Mass measurement error can falsely increase actual yield.
18. E – If 50 g is 50%, theoretical is 100%.
19. C – Percent yield compares actual to theoretical (possible) product.
20. D – 60% of 150 g = 90 g.
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