Chemistry / Unit 3 Chem 0489 worked example, 60 to 90 seconds
Calculating Percent Yield
The idea
Calculating percent yield means first finding the theoretical yield from the limiting reactant, then dividing the reaction's actual, measured yield by that theoretical value and multiplying by 100.
In practice
Reacting 32.9 g of CCl4 with excess HF is predicted, from the balanced equation and CCl4's identity as the limiting reactant, to give a theoretical yield of about 25.9 g of the product CF2Cl2. If the reaction actually produces 12.5 g of CF2Cl2 once isolated and weighed, dividing 12.5 g by 25.9 g and multiplying by 100 gives a percent yield of about 48.3%, well below the theoretical ceiling.
Where people slip
Dividing the theoretical yield by the actual yield, instead of the reverse, inverts the ratio and can produce a nonsensical result well above 100%.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Something wrong in this lesson? Flag it · Sources for Chemistry