Percentage Yield Calculations
The yield in a chemical reaction is the quantity of product obtained. The actual
yield can be compared, as a percentage, with the theoretical.
Worked Example 1
5g of methanol reacts with excess ethanoic acid to produce 9.6g of methyl
ethanoate. Calculate the percentage yield.
Step 1: determine the theoretical yield (the quantity expected from the
balanced equation)
CH3OH + CH3COOH CH3OOCCH3
1 mol 1 mol
32g 74g
5g 74 x 5
32
= 11.56g
Theoretical Yield = 11.56g
Step 2: The actual yield is always given in the question.
Actual yield = 9.6g
Step 3: Percentage yield = 9.6 x 100
11.56
= 83%
The percentage yield is a very important consideration for industrial chemists.
They must take account of cost of raw materials, plant-running costs etc. If the
yield of product is not sufficient enough to cover the costs of production then the
process would not be considered to be economically viable.
