Percent Yield
Here you'll learn how to find the Percentage Yield!
Yield is the amount of product obtained in a chemical reaction, but in chemical reactions you don't always get the predicted yield.
Percent yield is what percent of the Theoretical yield you actually get.
You can relate this to actual situations.
Lets say you're putting on a puppet show, with one puppet for each person.
You have 6 puppets and 4 people, so your theoretical yield would be 4 because the people are your limiting reagent.
BUT, on the day of the show, one of the people gets sick and can't perform, your actual yield would be 3.
If you give this a percentage, that would be your percent yield.
The equation is: percent yield=(actual yield/theoretical yield)x100
In this case: percent yield=(3 performers/4 performers)x100=75%
Your answer would be 75% is the percent yield!
Sadly, percentage yield for chemical reactions aren't as simple to calculate as puppets, but it's the same concept.
Lets say this is your question:
For the balanced equation shown below, if the reaction of 35.3 grams of O2 produces 36.1 grams of CO2, what is the percent yield?
C6H5Cl+7O2=>6CO2+2H2O+HCl
Okay!
So if you look at the question, it gives you the actual yield: "produces 36.1 grams of CO2"!
So your actual yield is 36.1g, that was easy!
Now you need to find the theoretical yield.
This means you need the limiting reagent to tell you how much CO2 you would (in theory) get.
Surprise! you are actually given the limiting reagent!
Well it doesn't directly say "__ is the limiting reagent", but you are only given grams for O2, so you'll have to assume this is the limiting reagent.
You can just look at the O2 and find the number of moles:
C6H5Cl+7O2
35.3g
32
1.103mol
And now you want to know how many moles of CO2 there are for each mole of O2, do this by making a ratio:
O2 : CO2
7 : 6
1 : 6/7
1.103 : 0.945
Now find out how many grams of CO2 there are by multiplying by the GFW.If you don't know what the GFW is, or how to find it click here.
In this case the GFW is 44:
mol=gram/gfw
grams=mol x gfw
0.945x44=41.58g <- this is your theoretical yield!
Now you can plug the numbers into the equation for percent yield:
percent yield=(actual yield/theoretical yield)x100
percent yield=(36.1g/41.58g)x100= 86.8%
So the answer is 86.8%!
Make sense? Why don't we try another problem?
Here's the question:
For the balanced equation shown below, if the reaction of 2.81 grams of O2 produces a 44.3% yield, how many grams of Na2O would be produced?
4Na+O2=>2Na2O
WHAAA! IT'S DIFFERENT! WHAT TO DO!
actual yield=(percent yield/100)xTheoretical yield
Oh that wasn't so difficult.
This question is asking for the actual yield, and you are already given the percent yield "produces a 44.3% yield"
You just have to find the theoretical yield.
Assume the limiting reagent is O2 and find the number of moles:
4Na+O2
2.81g
32
0.088mol
Now you want to know how many moles of Na2O there are for each mole of O2, do this by making a ratio:
O2 : Na2O
1 : 2
0.088 : 0.176
Now find out how many grams of Na2O there are by multiplying by the GFW.
If you don't know what the GFW is, or how to find it click here.
In this case the GFW is 62:
mol=gram/gfw
grams=mol x gfw
0.176x62=10.912g <- this is your theoretical yield!
Now you can plug the numbers into the equation for actual yield:
actual yield=(percent yield/100)xTheoretical yield
actual yield=(44.3%/100)x10.912g=4.834g
So the answer is 4.834 grams!
Make sense? How about practicing yourself?
Click here for a short quiz!
Yield is the amount of product obtained in a chemical reaction, but in chemical reactions you don't always get the predicted yield.
Percent yield is what percent of the Theoretical yield you actually get.
You can relate this to actual situations.
Lets say you're putting on a puppet show, with one puppet for each person.
You have 6 puppets and 4 people, so your theoretical yield would be 4 because the people are your limiting reagent.
BUT, on the day of the show, one of the people gets sick and can't perform, your actual yield would be 3.
If you give this a percentage, that would be your percent yield.
The equation is: percent yield=(actual yield/theoretical yield)x100
In this case: percent yield=(3 performers/4 performers)x100=75%
Your answer would be 75% is the percent yield!
Sadly, percentage yield for chemical reactions aren't as simple to calculate as puppets, but it's the same concept.
Lets say this is your question:
For the balanced equation shown below, if the reaction of 35.3 grams of O2 produces 36.1 grams of CO2, what is the percent yield?
C6H5Cl+7O2=>6CO2+2H2O+HCl
Okay!
So if you look at the question, it gives you the actual yield: "produces 36.1 grams of CO2"!
So your actual yield is 36.1g, that was easy!
Now you need to find the theoretical yield.
This means you need the limiting reagent to tell you how much CO2 you would (in theory) get.
Surprise! you are actually given the limiting reagent!
Well it doesn't directly say "__ is the limiting reagent", but you are only given grams for O2, so you'll have to assume this is the limiting reagent.
You can just look at the O2 and find the number of moles:
C6H5Cl+7O2
35.3g
32
1.103mol
And now you want to know how many moles of CO2 there are for each mole of O2, do this by making a ratio:
O2 : CO2
7 : 6
1 : 6/7
1.103 : 0.945
Now find out how many grams of CO2 there are by multiplying by the GFW.If you don't know what the GFW is, or how to find it click here.
In this case the GFW is 44:
mol=gram/gfw
grams=mol x gfw
0.945x44=41.58g <- this is your theoretical yield!
Now you can plug the numbers into the equation for percent yield:
percent yield=(actual yield/theoretical yield)x100
percent yield=(36.1g/41.58g)x100= 86.8%
So the answer is 86.8%!
Make sense? Why don't we try another problem?
Here's the question:
For the balanced equation shown below, if the reaction of 2.81 grams of O2 produces a 44.3% yield, how many grams of Na2O would be produced?
4Na+O2=>2Na2O
WHAAA! IT'S DIFFERENT! WHAT TO DO!
actual yield=(percent yield/100)xTheoretical yield
Oh that wasn't so difficult.
This question is asking for the actual yield, and you are already given the percent yield "produces a 44.3% yield"
You just have to find the theoretical yield.
Assume the limiting reagent is O2 and find the number of moles:
4Na+O2
2.81g
32
0.088mol
Now you want to know how many moles of Na2O there are for each mole of O2, do this by making a ratio:
O2 : Na2O
1 : 2
0.088 : 0.176
Now find out how many grams of Na2O there are by multiplying by the GFW.
If you don't know what the GFW is, or how to find it click here.
In this case the GFW is 62:
mol=gram/gfw
grams=mol x gfw
0.176x62=10.912g <- this is your theoretical yield!
Now you can plug the numbers into the equation for actual yield:
actual yield=(percent yield/100)xTheoretical yield
actual yield=(44.3%/100)x10.912g=4.834g
So the answer is 4.834 grams!
Make sense? How about practicing yourself?
Click here for a short quiz!