C3e - Percentage yield and atom economy

Question 1

What is percentage yield and its formula

Answer 1

ratio between the actual yield with the predicted yield

% yield = (actual yield / predicted yield) * 100

Question 2

Explain why an industrial process wants as high a percentage yield as possible (2)

Answer 2

higher % yield means less reactants wasted, important in industry as it saves money

higher %yield means more product obtained per reactant, so lower average cost per product

Question 3

Possible reasons why the percentage yield of a product is less than 100% (4)

Answer 3

loss in filtration; some liquid/solid left on filter paper

loss of liquids in evaporation (esp when heated)

loss in transferring liquids; liquid left on inner surface of container

not all reactants react to make product; reversible reactions, products turn back to reactants (Haber)

Question 4

What is the formula for atom economy

Answer 4

(relative formula mass of desired product / total relative formula mass of all products) * 100

Question 5

Explain why an industrial process wants as high an atom economy as possible(2)

Answer 5

Reduce the production of unwanted products that will need to be disposed of, which often adds to overall costs

Makes the process more sustainable by making better use of the reactants, so conserving raw materials and avoiding the need to get rid of wasted products