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# How to Calculate Percent Yield in Chemistry

## Expert Review By:

❶I managed to answer my question by just following steps in part 2 and part 3.   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.

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. Calculate the molar mass of each reactant and convert the amount of each reactant from grams to moles. Divide the moles of one reactant with the moles of the other to find the ratio of the 2 molecules, then find the ideal ratio for the reaction.

Compare the ratios to find the limiting reactant. Start with a balanced chemical equation. A chemical equation describes the reactants on the left side reacting to form products on the right side. Some problems will give you this equation, while others ask you to write it out yourself, such as for a word problem. Since atoms are not created or destroyed during a chemical reaction, each element should have the same number of atoms on the left and right side. The equation is balanced.

Read this guide if you are asked to balance an equation yourself. Calculate the molar mass of each reactant. Look up the molar mass of each atom in the compound, then add them together to find the molar mass of that compound.

Do this for a single molecule of the compound. You can find a more precise value on a periodic table. Convert the amount of each reactant from grams to moles. Now it's time to look at the specific experiment you are studying. Write down the amounts of each reactant in grams. 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. 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. Write down the amounts of each reactant in grams.

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. 