1. % Yield Definitions 1. Theoretical Yield
The maximum amount of product that can be formed from a given amount of reactants
In other words, the calculated amount predicted through stoichiometry

2. % Yield Definitions Actual Yield
The amount that is actually formed when the reaction is carried out in the laboratory.

3. % Yield = actual yield X 100 theoretical yield
% yield will never be over 100%
Most likely it will never even be 100%

4. Why will % yield never be 100%
Advantageous to add an excess of an inexpensive reagent to ensure that all of the more expensive reagents react
Reactant may not be 100% pure
Materials are lost during the reaction
If a reactions takes place in a solution it may be impossible to get all of the reactants or products out of the solution
If the reactions takes place at a high temperature, materials may be vaporized and escape into the air
Side reactions may occur
Example Mg burned in air. Some of Mg reacts with nitrogen reducing the amount of MgO produced.
Loss of product when filtering or transferring
If reactants are not carefully measured

5. % yield example problem
In a reaction between barium chloride and potassium sulfate, 3.89 g of barium sulfate is produced from 3.75 g of barium chloride. What is the percent yield?

6. % yield example problem answer
BaCl2 + K2SO4 --> BaSO KCl
3. 75 g BaCl2 1 mol BaCl mol BaSO g BaSO4
208.3 g BaCl2 1 mol BaCl mol BaSO4
= 4.20 g BaSO4
3.89 g BaSO4 x = %
4.20 g BaSO4

7. % yield example problem your turn
13.35 grams of magnesium hydroxide is produced when grams of magnesium nitrate reacts with an excess of aluminum hydroxide. What is the percent yield?

8. % yield example problem answer
3 Mg(NO3)2 + 2 Al(OH)3 --> 3 Mg(OH)2 + 2 Al(NO3)3
42.50g Mg(NO3)2 1mol Mg(NO3) mol Mg(OH) g Mg(OH)2
148.3g Mg(NO3) mol Mg(NO3)2 1mol Mg(OH)2
= g Mg(OH)2
% yield = g Mg(OH)2 x = % Mg(OH)2
16.71 g Mg(OH)2