1. Unit 8: Percent Yield Calculations

2. Formula for Percent Yield:
Actual (also called Experimental yield)
Theoretical Yield
X 100

3. Theoretical yield: What should have been produced in the reaction.
Actual (Experimental) yield: What was actually produced in the reaction. This is given to you in the problem. It is not placed into the BCA chart.
Theoretical yield: What should have been produced in the reaction.
What we have been calculating to this point (i.e. on worksheets 8.1 and 8.15) has been theoretical yield. We just have not been referring to our answers with this term.

4. Example
#4 on Unit 8.2
Suppose 4.61 g of zinc was allowed to react with hydrochloric acid to produce zinc chloride and hydrogen gas. How much zinc chloride should you get?
Suppose that you actually recovered 8.56 g of zinc chloride. What is your percent yield?
Balanced Equation:
  Zn HCl  ZnCl H2
Before
Change
After

5. First convert grams of Zinc to moles:
4.61 g Zn 1.00 mol Zn g of Zn X
= mol Zn

6. Complete the BCA Balanced Equation: Zn + 2HCl  ZnCl2 + H2
Before xs
Change
After xs

7. Calculate Theoretical Yield:
The BCA amounts calculated are “theoretical” values based off of the given reactant value.
Convert the moles of zinc chloride to grams. You do this due to being given a gram amount of the product (actual yield).
0.0705mol ZnCl g of ZnCl2
mol ZnCl2
= g Zn X

8. Calculate Percent Yield:
8.56 g ZnCl2 (Experimental yield…given) 9.61 g ZnCl2 (Theoretical yield…calculated) This is your final answer to Problem #4
= 89.1%
X 100