RPAL Theoretical Yield 2 — Questions and Answers
Question 1: What assumption underlies the theoretical yield calculation?
- The reaction proceeds to completion with 100% conversion of limiting reagent to product (Correct answer)
- Some limiting reagent always remains unreacted
- The reaction temperature affects the amount of product
- The excess reagent contributes equally to product formation
Correct answer: The reaction proceeds to completion with 100% conversion of limiting reagent to product
Theoretical yield assumes all of the limiting reagent is converted to product with no side reactions or losses.
Question 2: In 2C + O₂ → 2CO, if 4 mol C and 1 mol O₂ react, what is the theoretical yield of CO?
- 2 mol CO (Correct answer)
- 4 mol CO
- 1 mol CO
- 3 mol CO
Correct answer: 2 mol CO
O₂ is limiting (1 mol O₂ for 2 mol C needed, but 4 mol C present); 1 mol O₂ produces 2 mol CO from the 1:2 ratio.
Question 3: A student calculates a theoretical yield of 8.5 g for a product with a molar mass of 17 g/mol. How many moles of product does this represent?
- 0.5 mol (Correct answer)
- 5.0 mol
- 144.5 mol
- 0.05 mol
Correct answer: 0.5 mol
8.5 g ÷ 17 g/mol = 0.5 mol of product.
Question 4: Which of the following would NOT change the theoretical yield?
- Adding more excess reagent (Correct answer)
- Adding more limiting reagent
- Changing the stoichiometry of the balanced equation
- Changing the identity of the product
Correct answer: Adding more excess reagent
Adding more of the excess reagent does not increase theoretical yield because the limiting reagent still controls product formation.
Question 5: For CaCO₃ → CaO + CO₂, if 100 g of CaCO₃ (molar mass = 100 g/mol) reacts completely, what is the theoretical yield of CO₂ (molar mass = 44 g/mol)?
- 44 g (Correct answer)
- 100 g
- 56 g
- 22 g
Correct answer: 44 g
100 g CaCO₃ = 1 mol; the 1:1 ratio gives 1 mol CO₂; 1 mol × 44 g/mol = 44 g CO₂.
Question 6: Why is the theoretical yield considered an 'ideal' value?
- Because it assumes perfect conditions with no product lost to side reactions or handling (Correct answer)
- Because it is calculated using ideal gas conditions
- Because only ideal solutions can achieve this yield
- Because it is always larger than the limiting reagent mass
Correct answer: Because it assumes perfect conditions with no product lost to side reactions or handling
Theoretical yield represents a best-case scenario that rarely occurs in practice due to side reactions, incomplete reactions, and product losses during purification.
RPAL Theoretical Yield 2
What assumption underlies the theoretical yield calculation?