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# How to Calculate Percent Yield in Chemistry

❶Convert the result to grams. Quick Summary To calculate a percentage yield in chemistry, start with a balanced chemical equation, with the reactants on the left side and the products on the right.

## Sample Calculation

Divide this value by that compound's molar mass to convert the amount to moles. Find the ratio of your reactions. A mole is an exact number for the amount of a substance and it is equal to 6.

You now know how many molecules of each reactant you started with. Divide the moles of 1 reactant with the moles of the other to find the ratio of the 2 molecules. You started with 1. The ratio of oxygen to glucose molecules is 1. This means you started with 9 molecules of oxygen for every 1 molecule of glucose. Find the ideal ratio for the reaction.

Go back to the balanced equation you wrote down earlier. This balanced equation tells you the ideal ratio of molecules: The coefficients tell you there are 6 oxygen molecules and 1 glucose molecule. Make sure you list the reactants in the same order you did for the other ratio.

In a chemical reaction, 1 of the reactants gets used up before the others. The quantity of the product that is created in the reaction is limited by the reagent. Compare the 2 ratios you calculated to identify the limiting reactant: The bottom reactant in the ratio is the limiting reactant.

If the actual ratio is smaller than the ideal ratio, you don't have enough of the top reactant, so it is the limiting reactant. The bottom reactant, glucose, must be the limiting reactant. Part Two of Three: Identify your desired product. The right side of a chemical equation lists the products created by the reaction. Each product has a theoretical yield, meaning the amount of product you would expect to get if the reaction is perfectly efficient. The right-hand side lists 2 products, carbon dioxide and water.

Write down the number of moles of your limiting reactant. The theoretical yield of an experiment is the amount of product created in perfect conditions. To calculate this value, begin with the amount of limiting reactant in moles. This process is described above in the instructions for finding the limiting reactant. In the example above, you discovered that glucose was the limiting reactant. You also calculated that you started with 0.

Find the ratio of molecules in your product and reactant. Return to the balanced equation. Divide the number of molecules of your desired product by the number of molecules of your limiting reactant.

In other words, this reaction can produce 6 molecules of carbon dioxide from 1 molecule of glucose. Multiply the ratio by the reactant's quantity in moles. The answer is the theoretical yield of the desired product in moles. You started with 0. The theoretical yield of carbon dioxide is 0. Convert the result to grams. Multiply your answer in moles by the molar mass of that compound to find the theoretical yield in grams. This is a more convenient unit to use in most experiments. The theoretical yield of the experiment is Part Three of Three: The theoretical yield you calculated assumes that everything went perfectly.

In an actual experiment, this never happens: This is why chemists use 3 different concepts to refer to yield: The theoretical yield is the maximum amount of product the experiment could make. The actual yield is the actual amount you created, measured directly on a scale. Write down the actual yield of the experiment.

If you performed the experiment yourself, gather the purified product from your reaction and weigh it on a balance to calculate its mass. If you are working on a homework problem or someone else's notes, the actual yield should be listed. Divide the actual yield by the theoretical yield. Make sure you use the same units for both values typically grams.

To determine percent yield, divide the actual yield by the theoretical yield and multiply by For this example, use the equation: This percentage tells you the efficiency of the chemical reaction, or how good the reaction is at actually producing the desired product. High percentages such as this one indicate better yields, and low percentages indicate poor yields.

Ezell is a certified high school science teacher of 16 years with experience in grades seven through twelve. In addition to teaching in the public school setting, Ezell is also an online science instructor for the Alabama State Department of Education. With a Bachelor of Science in comprehensive science education and a Master of Education in instructional technology from Troy University in Alabama, Ezell has a wealth of knowledge and experience in the education field.

Ezell; Updated April 24, Here's a Calculator to Help You X. Matter and Change; Laurel Dingrando, et al. How to Calculate Percent Yield.