Percent Yield

Percent yield describes the efficiency of a chemical reaction 100 free throws Theoretically… Actually…

Chemical reactions also have theoretical and actual outcomes Reasons for not producing theoretical amounts: – Reactants or products might stick to container

Reasons for not producing theoretical amounts: – Reactants or products might evaporate

Reasons for not producing theoretical amounts: – Other unintended products might form

Reasons for not producing theoretical amounts: – Purification process might reduce reactant amounts

Because of these problems, scientists need to know how to gage the yield of a chemical reaction

Theoretical yield Maximum amount of product that can be produced from a given amount of reactant N H 2 → 2 NH 3

Actual yield Amount of product produced when a chemical reaction is carried out in an experiment

Popcorn If there are 100 kernels in a bag… – What is the theoretical yield? – What is the actual yield?

Percent yield Ratio of the actual yield to the theoretical yield shown as percent

Percent yield If there are 105 kernels in a bag of popcorn and 13 were left unpopped, what is the percent yield of that bag? 92/105 = 87.6 %

Now apply this to chemistry… Solid silver chromate (Ag₂CrO₄) forms when potassium chromate (K₂CrO₄) is added to a solution containing g of silver nitrate (AgNO₃). Determine the theoretical yield of Ag₂CrO₄. Write out the equation and balance it!

2AgNO₃ + K₂CrO₄ = Ag₂CrO₄ +2KNO₃ Change grams to moles then use mole ratios to find out how much product it will produce g / g = mol x 1 mol Ag₂CrO₄ = mol Ag₂CrO₄ 2 mol AgNO₃ g?

2AgNO₃ + K₂CrO₄ = Ag₂CrO₄ +2KNO₃ Change moles to grams mol Ag₂CrO₄ x g = g Ag₂CrO₄ g? Theoretical yield

If the experiment is performed and the actual yield is g Ag₂CrO₄, what is the percent yield? g g x 100 = 93.2% Ag₂CrO₄

Popcorn time!!!