Introduction to Percentage Yield/Theoretical Yield/Actual Yield
In real life, you dont actually get the amount of the product which is predicted using the limiting reagent. To find out how much of the actual product is produced, you use the formula, Percentage Yield= (Actual Yield/Theoretical Yield) X 100. The Percentage Yield is the percent of the Theoretical yield which is actually produced. The Theoretical Yield is the answer you gain from using the limiting reagent. And the Actual yield, is the actual amount of product you get.
Heres an example problem.
For the balanced equation shown below, if the reaction of 70.5 grams of CH5N produces a 37.1% yield, how many grams of CO2 would be produced ?
4CH5N+13O2=>4CO2+10H2O+4NO2
CH5N= Limiting Reagent ( the chemical which is reacting to make the product)
In most cases, you will be asked to find the Theoretical Yield. To do this i use the following formula.
Theoretical Yield= (Molar Mass of Product X its ratio number/ Molar Mass of the Reactant X its ratio number) grams of the reactant
Step 1: Identify what you must find to solve for the equation.
The question has give you 37.1= Actual Yield/Theoretical Yield. So they are expecting you to find the actual yield, because you must assume in most cases they assume you will be able to find the theoretical yield.
Step 2: Write out your formulas
37.1= (Actual Yield/Theoretical Yield) X 100
and
Theoretical Yield= (MM of P= (44) X 4/MM of R= (31) X 4) Grams of LR= 70.5
Step 3: Solve the equation for Theoretical Yield so that you will be able to find the Actual Yield
Theoretical Yield= (176/124) X 70.5
Theoretical Yield= 1.419 X 70.5
Theoretical Yield = 100.06
Step 4 (final step): Plug the Theoretical Yield into your Percentage Yield formula so that you will be able to find you unkown variable.
37.1= (Actual Yield/100.06) X 100
Divide By 100 on each side.
.371= Actual Yield/100.6
Multiply each side by 100.6 so that you may be able to get your actual yield
Actual Yield= 37.32 grams
