The percent yield of your chemical reaction represents how efficiently the reactants can be transformed into products. A larger percent yield means more product(s) have been formed.
Where do we begin?
Before you can calculate your percent yield you must first use stoichiometry and a balanced equation to determine the theoretical yield of the limiting reactant.
I'll be showing you how to solve these types of problems using a very common example question:
"If 45.0 g benzene reacts with excess oxygen to produce 112 g carbon dioxide, what is the percent yield of the reaction?"
Within our calculations we will ignore both oxygen and water because they are either in excess or not addressed within the question.
STEP 1: Calculate the molar masses of C6H6 and CO2.
STEP 2: Convert the grams of C6H6 into moles of C6H6.
STEP 3: Convert the moles of C6H6 into moles of CO2 by doing a mole-to-mole ratio.
Bring down the coefficients from the balanced equation.
STEP 4: Convert the moles of CO2 into grams of CO2.
STEP 5: Calculate the percent yield.
The actual yield represents the amount of product that is made, isolated or produced when doing the reaction in real life. The actual yield would be the 112 grams of carbon dioxide.
The theoretical yield represents the maximum amount of product that could be made, but in reality we never obtain that amount. Some product is always lost through isolation, purification, transfer or some other uncontrollable variable.
Calculations involving experimental error or percent error.
The larger the percent error value then the less precise our calculations.
Percent recovery deals with the purification of a chemical sample.
If hypothetically our 112 grams of carbon dioxide was expelled from 546 grams of sedimentary rock.