RPAL Theoretical Yield 1 — Questions and Answers
Question 1: What is theoretical yield?
- The maximum amount of product that can be formed from the limiting reagent (Correct answer)
- The actual amount of product collected in the lab
- The amount of excess reagent that remains
- The minimum amount of product that can form
Correct answer: The maximum amount of product that can be formed from the limiting reagent
Theoretical yield is the calculated maximum product assuming all of the limiting reagent is converted to product with no losses.
Question 2: Which reagent is used to calculate theoretical yield?
- The limiting reagent (Correct answer)
- The excess reagent
- The largest reactant by mass
- The product itself
Correct answer: The limiting reagent
Since the limiting reagent controls how much product forms, theoretical yield is always calculated from the limiting reagent's moles.
Question 3: In the reaction 2H₂ + O₂ → 2H₂O, if O₂ is the limiting reagent with 2 mol, what is the theoretical yield of H₂O?
- 4 mol H₂O (Correct answer)
- 2 mol H₂O
- 1 mol H₂O
- 3 mol H₂O
Correct answer: 4 mol H₂O
The 1:2 ratio of O₂ to H₂O means 2 mol O₂ produces 2 × 2 = 4 mol H₂O.
Question 4: What conversion is needed to express theoretical yield in grams?
- Multiply moles of product by its molar mass (Correct answer)
- Divide moles of product by its molar mass
- Multiply moles of limiting reagent by Avogadro's number
- Add molar masses of all reactants
Correct answer: Multiply moles of product by its molar mass
Converting moles of product to grams requires multiplying by the product's molar mass (g/mol).
Question 5: If the theoretical yield of a reaction is 50 g but only 40 g is collected, what does this indicate?
- The reaction was less than 100% efficient — some product was lost (Correct answer)
- The theoretical yield calculation was wrong
- The limiting reagent was not fully consumed
- The reaction produced more than expected
Correct answer: The reaction was less than 100% efficient — some product was lost
Collecting less than theoretical yield is normal; it indicates product loss due to side reactions, incomplete reaction, or handling errors.
Question 6: For N₂ + 3H₂ → 2NH₃, if H₂ is limiting at 6 mol, what is the theoretical yield of NH₃?
- 4 mol (Correct answer)
- 6 mol
- 2 mol
- 3 mol
Correct answer: 4 mol
The 3:2 ratio of H₂ to NH₃ means 6 mol H₂ produces (6 × 2/3) = 4 mol NH₃.
RPAL Theoretical Yield 1
What is theoretical yield?