Percentage Yield And Atom Economy

Question 1

What is a yield?

Answer 1

The AMOUNT made.

Question 2

Why are RFM used in percentage yield calculations?

Answer 2

They can help to predict how much product (predicted yield) should be made in a chemical reaction.

Question 3

Why is the actual yield less compared to the predicted yield?

Answer 3

Due to practical methods such as heat loss, reversible reactions and product being lost when it is removed from the reaction mixture.

Question 4

How do you calculate the percentage yield?

Answer 4

• Actual yield
  —————- X 100
  Predicted yield

Question 5

Why does industry want a high percentage yield?

Answer 5

• Reduce the amount of reactants wasted because this is wasteful - increases sustainability.
• Reduce costs because it ensures that enough reactants are used. Using too little would result in a reduced amount of product being made.

Question 6

What is atom economy?

Answer 6

A way of measuring how many atoms are wasted or lost during a chemical reaction. It is a measure of how many atoms in the starting reactants end up in the final product.

Question 7

What does a 100% aom economy mean?

Answer 7

All the atoms in the reactants have been converted to the desired product.
- Companies aim for this as it is a ‘greener’ process.

Question 8

Why do industrial processes want as high a atom economy as possible?

Answer 8

• Makes the process more sustainable by making making better use of the products. This conserves raw materials and avoids the need to get rid of waste product.
• Reduces the production of unwanted products that need to be disposed of. Disposing of these products adds to the overall costs.

Question 9

How do you calculate the atom economy?

Answer 9

• Mr of desired products
  ——————————- X 100
  Sum of Mr of all products

Question 10

What is percentage yield?

Answer 10

The percentage of actual product made in a chemical reaction compared to the amount which could be ideally made.