Yield Flashcards

All 5 cards in this deck

What is the formula for percentage yield?

$\text{percentage yield} = \dfrac{\text{actual yield}}{\text{theoretical yield}} \times 100$

What is meant by the theoretical yield of a reaction?

The maximum mass of product that could be made from the given amounts of reactants, calculated from the balanced equation.

State three causes of the actual yield of a reaction being less than the theoretical yield.

Incomplete reaction; practical losses during the experiment; competing, unwanted side reactions.

What are the steps to calculate percentage yield from a balanced equation?

e.g. the equation predicts $0.20$ mol of a product of $M_r = 80$, and $12\ \mathrm{g}$ is actually made

1. Use the equation ratio to find moles of product: $0.20$ mol
2. Theoretical yield = moles $\times M_r$ = $0.20 \times 80 = 16\ \mathrm{g}$
3. Percentage yield = $\dfrac{12}{16} \times 100 = 75\%$

True or false? A percentage yield greater than 100% shows the reaction was very efficient.

False. The actual yield cannot exceed the theoretical yield — a value over 100% means the product is impure or still wet.