Percentage Yield & Atom Economy

Question 1

How do we calculate percentage yield?

Answer 1

Percentage yield = (actual yield/ maximum theoretical yield) x 100.

Question 2

Why is it rare to achieve 100% yield? (3)

Answer 2

1. product lost when separated from reaction mixture.
2. reactants may react differently than expected - may not get product we expect.
3. Reversible reactions may not react to completion.

Question 3

What is atom economy? (2)

Answer 3

1. AKA atom utilisation - a measure of the amount of reactants that form useful products - used to decide which reactions are the most efficient
2. no waste products = 100% atom economy.

Question 4

Why is high atom economy useful? (2)

Answer 4

1. Minimising the production of waste saves money.

2. Increases sustainability by not wasting resources

Question 5

What is the formula for atom economy? (2)

Answer 5

1. Atom economy = RFM of desired products (from equation) ÷ the sum of RFM of all reactants (from equation) x 100
2. “From equation” means that the big numbers in front count too.