theoretical yeald/using limiting reagents

Congratulations on completing finding the limiting reagants, you are over the first hurdle!

The theoretical yield is basically us doing our calculations in a perfect world and how much the product would be synthesized in our ideal situation.

So let’s find the theoretical yield using an example problem once again:

Example

For the balanced equation shown below, if 96.1 grams of C₃H₈ were reacted with 267 grams of O₂, how many grams of H₂O would be produced?

C₃H₈+5O₂=>3CO₂+4H₂O

For the theoretical yield you basically follow the same steps of limiting reagents but add a few extra things on to the end!

1.  Look at your most important information:

96.1 grams of C₃H₈

267 grams of O₂

how many grams will be produced: H₂O

            2.     Find the limiting reagent

If you need to remind yourself the steps for doing this just click here…

The limiting reagent is: O₂

             3.   Find the molar mass of the element that we are trying to determine how many grams will be produced:

If you need a reminder on molar masses click here…

H₂O has a molar mass of 18

                4.     Multiply the moles of the limiting reagent which you found in step 2 (when finding the limiting reagent) by the molar mass of the of the product                                         where we are finding out how many grams will be produced

Moles of O₂ * molar mass of H₂O

8.34 * 18 = 150.12

                5.     Now you have to compare the ratios of the limiting reagent with the product where we are finding out how many grams will be produced

If you need a reminder on ratios click here…

      So if we look back to the equation:

             5O₂ : 4H₂O

The ratio is 5:4

-       You aim is to make the left side of the ratio bracket 1

-       So divide both sides by 5

-       1:0.8

o   the new ratio is

o   O₂ : H₂O

o   1:0.8

                   6.     Finally, multiply whatever is on the right side of your ratio by the answer you found in step # 4

On the right side of our ratio is 0.8 multiplied by our answer in step # 4 which was 150.12

0.8 * 150.12 = 120.1

And we have our correct answer! = 120.1

So now you have learnt all about theoretical yield, let’s put this knowledge to the test.

Click here for the practice theoretical yield problems..