1. Chapter 7
7.3: Percentage Yield

2. Theoretical Yield vs. Actual Yield
Theoretical yield: the amount of product predicted by stoichiometry
Actual yield: the amount of product obtained by experiment

3. Theoretical Yield vs. Actual Yield
Why do they differ?
- Imperfect techniques
- Impure reactants
- Competing reactions
Competing reaction: a reaction that occurs at the same time and involves the same reactants and products.
Chemists have a percentage that is used to express the “success” of a reaction. This percentage is called the percentage yield.

4. Percentage Yield
Percentage yield: compares the actual yield with the theoretical yield
% yield= AY x 100 TY

5. Percentage Yield
Sample Problem #1 N2(g) +3H2(g)  2NH3(g) When 75.0g of nitrogen reacts with sufficient hydrogen, the theoretical yield of ammonia is 9.10g. If 2.14g of ammonia is obtained by experiment, what is the percentage yield of the reaction? (Ans: 23.5%)

6. Percentage Yield Sample Problem #2 2P(s) + 3Cl2(g)  2PCl3(l)
7.50g of chlorine is reacted with excess phosphorus.
What is the theoretical yield of PCl3 for this reaction?
(Ans: 9.71g)
b) If 1.25g of PCl3 is produced, what is the percentage yield?
(Ans: 12.9%)

7. Predicting Actual Yield
Sample Problem #3
C3H8(g) + 5O2 (g) → 3CO2 (g) + 4H2O (g)
37.0g of oxygen reacts with excess propane (C3H8) . If the percentage yield is 94.0%, how much carbon dioxide is produced?
(Ans: 28.8g)
Step 1: find theoretical yield
Answer: 30.6g
Step 2: find actual yield
Answer: 28.8g

8. Inv 7A – due next class…lab quiz **TEST Unit 3 (Ch 5-7) in 3 days**
Textbook p 262 #31-33 p 266 #34-37
Inv 7B
- Complete prediction
- Copy obs table Read
(formal report)
Reminders:
Inv 7A – due next class…lab quiz
**TEST Unit 3 (Ch 5-7) in 3 days**