Percentage Yield

Congratulations you are at the final part of knowing all you need to know from me about Limiting reagents!

So now you know all about theoretical yield which is our ideal and perfect world. Unfortunately the industry doesn’t function in this way and we have to work around it another way. So in the real world we must sacrifice the efficiency of the theoretical yield and stick with the fastest but not most efficient way the manufacturers can produce.

So instead we have the actual yield, which is how much product is actually synthesized during the experiment.

How efficient it is we determine using the percentage yield which can range from being 0% which is obviously atrocious to 100% which would be perfect. The percentage yield is the ratio between the actual yield and the theoretical yield multiplied by 100%.

Here is the equation:

Percentage yield = actual yield/ theoretical yield * 100

So let’s do a finding the % yield problem together:

Example

For the balanced equation shown below, if the reaction of 67.1 grams of CH₄S produces 74.0 grams of SO₃, what is the percent yield?

2CH₄S+7O₂=>2CO₂+4H₂O+2SO3

So you are given the actual yield, this is always what comes after produces…

Actual yield: 74.0 grams of SO₃

To find the theoretical yield you just follow the exact same steps from before but you are already given the limiting reagent here….

Look back at how to find the theoretical yield by clicking here for a more detailed explanation…

67.1 grams of CH₄S

74.0 grams of SO₃

67.1 grams of CH₄S/ molar mass of CH₄S:  48 = 1.4mol

limiting reagent is given to you in the question: CH₄S

- Find the molar mass of the element that we are told how many grams is produced of it:

Molar mass of SO₃:  80

-       Multiply the moles of the limiting reagent which by the molar mass of the of the product which we are given

1.4 moles * 80 = 112

-       Now you have to compare the ratios of the limiting reagent with the product where we are given how many grams will be produced

2CH₄S : 2SO3

2:2

1:1

the ratio is 1:1 so you don’t have to multiply it at all

the theoretical yield is just 112

Notice how these are the same exact steps that you learnt before…

NOW for the new stuff, we have the actual and theoretical yield so we just need to use the formula to find the % yield:

Percentage yield = actual yield/ theoretical yield * 100

Percentage yield = 74/ 112 * 100 = 66%

Easy peasy!... So now click here and try some practicing percentage yield problems for yourself!