RPAL Percent Yield 1 — Questions and Answers
Question 1: What is percent yield?
- The ratio of actual yield to theoretical yield expressed as a percentage (Correct answer)
- The ratio of limiting reagent to excess reagent
- The percentage of reactants converted to products at equilibrium
- The fraction of product lost during the reaction
Correct answer: The ratio of actual yield to theoretical yield expressed as a percentage
Percent yield = (actual yield / theoretical yield) × 100%, measuring how efficient a reaction was in the lab.
Question 2: What is the formula for percent yield?
- (Actual yield ÷ Theoretical yield) × 100% (Correct answer)
- (Theoretical yield ÷ Actual yield) × 100%
- (Actual yield − Theoretical yield) × 100%
- (Theoretical yield + Actual yield) ÷ 2
Correct answer: (Actual yield ÷ Theoretical yield) × 100%
Percent yield is calculated by dividing the actual yield by the theoretical yield and multiplying by 100%.
Question 3: If the theoretical yield is 50 g and the actual yield is 40 g, what is the percent yield?
- 80% (Correct answer)
- 125%
- 90%
- 40%
Correct answer: 80%
(40 g / 50 g) × 100% = 80% yield.
Question 4: Why is percent yield almost always less than 100%?
- Because of side reactions, product loss during purification, and incomplete reactions (Correct answer)
- Because theoretical yield is always overestimated
- Because the limiting reagent is never fully identified correctly
- Because Avogadro's number introduces rounding errors
Correct answer: Because of side reactions, product loss during purification, and incomplete reactions
Real reactions lose product through side reactions, handling losses, and incomplete conversion, making 100% yield essentially unattainable.
Question 5: A percent yield greater than 100% indicates what?
- An error — possibly impure product or incorrect theoretical yield calculation (Correct answer)
- An exceptionally efficient reaction
- The reaction produced extra atoms from the environment
- The actual yield was calculated incorrectly and is actually valid
Correct answer: An error — possibly impure product or incorrect theoretical yield calculation
A percent yield over 100% is physically impossible and signals experimental error such as product contamination or a miscalculated theoretical yield.
Question 6: Which of the following would increase the percent yield of a reaction?
- Reducing product loss during collection and purification (Correct answer)
- Adding more excess reagent
- Increasing the temperature of the reaction
- Using a larger container
Correct answer: Reducing product loss during collection and purification
Minimizing product loss during workup and purification is the most direct way to improve percent yield.
RPAL Percent Yield 1
What is percent yield?