# 8. Percentage yield ```Percentage yield
Learning objective
Perform calculations to
determine the percentage
yield of a reaction
• Key words:
• Percentage
yield
• Limiting reagent
When writing a fully balanced chemical equation, it is
assumed that ALL of the reactants will be converted
into products. If this were true then the yield would be
100%
The percentage yield can be calculated using the
formula:
𝑎𝑐𝑡𝑢𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡, 𝑖𝑛 𝑚𝑜𝑙, 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡
% 𝑦𝑖𝑒𝑙𝑑 =
𝑥 100
𝑡ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡, 𝑖𝑛 𝑚𝑜𝑙, 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡
Factors that affect the percentage yield:
• The reaction may be at equilibrium and may not go
to completion
• Other side reactions may occur, leading to byproducts
• The reactants may not be pure
• Some of the reactants or products may be left
behind in the apparatus used in the experiment
• Separation and purification may result in the loss of
some of the product
1. A student adds 200.0g of C7H6O3 to an excess of C4H6O3, this produces C9H8O4 and C2H4O2. Calculate
the percent yield if 231 g of aspirin (C9H8O4) is produced.
C7H6O3 + C4H6O3 
C9H8O4 + C2H4O2
2. According to the following equation, Calculate the percentage yield if 550.0 g of toluene ()added to an
excess of nitric acid () provides 305 g of the p-nitrotoluene product.
C7H8 + HNO3  C7H7NO2 + H2O
3. Aluminum reacts with an aqueous solution containing excess copper (II) sulfate. If 1.85 g Al reacts and the
percentage yield of Cu is 56.6%, what mol mass of Cu is produced?
Al + CuSO4 
Cu
+ Al2(SO4)3
4. The combustion of methane produces carbon dioxide and water. Assume that 2.0 mol of CH4 burned in
the presence of excess air. What is the percentage yield if the reaction produces 87.0 g of CO2?