Quantitative Chemistry: Percentage Yield

Question 1

What is the theoretical yield?

Answer 1

The volume of products you would get in theory if you were to calculate it.

Question 2

What is actual yield?

Answer 2

The volume of products you actually get

Question 3

How do you calculate percentage yield?

Answer 3

Actual yield
_____________ x 100
Theoretical yield

Question 4

What are the 3 main reasons for a lower actual yield?

Answer 4

1. Reactants may not all react
   If the reaction is slow then it may not have finished or if it‘s reversible then it ma have reached equilibrium.
2. Side reactions may have taken place
   Reactants could’ve produced a different product to the expected one each they could’ve reacted to oxygen in the air
3. Some of the product may have been lost in the process
   eg. gaseous products may escape and float away

Question 5

For the balanced equation shown below, if the reaction of 40.8 grams of C₆H₆O₃ produces a 39.0% yield, how many grams of H₂O would be produced ?

C₆H₆O₃ +6O₂ → 6CO₂ + 3H₂O

Answer 5

actual yield = 6.83 grams

Question 6

What is the percentage yield of NH₃ if 40.5g of NH₃ is produced from 20.0mol H₂ and excess N₂

Answer 6

1. Write the balanced equation
2. Calculate the theoretical amount of NH₃
3. Calculate the percentage yield of NH₃

40.5/227 x 100 =
17.8%