Converting to grams using the gram atomic weights from a periodic table of the elements gives the following weights: According to the equation in grams, 4 grams of hydrogen react with 32 grams of oxygen to form 36 grams of water, which is the theoretical yield of this reaction.
In real reactions, the actual yield is usually lower than the theoretical yield. The weights of the reactants may not be exactly balanced so the reaction products are less.
The reaction may not use all of one of the reactants because, as a gas, some is lost into the air. Sometimes the reactants have impurities that cause the reaction to stop, and sometimes the reaction product gets in the way of a complete reaction. For all these reasons, less product is produced than the theoretical maximum.
When the actual weight of the reaction product is less than the theoretical value, the result can be expressed as a percentage. The actual weight divided by the theoretical weight multiplied by gives the percent yield of the reaction. In the reaction of hydrogen and oxygen, the theoretical weight of the reaction product for 4 grams of hydrogen and 32 grams of oxygen was 36 grams of water. But in a real reaction, if 4 grams of hydrogen burns in air, the amount of water produced might only be 27 grams.
Dividing the actual value of 27 grams by the theoretical value of 36 grams and multiplying by gives 75 percent, the percent yield for this reaction. Bert Markgraf is a freelance writer with a strong science and engineering background. He started writing technical papers while working as an engineer in the s. More recently, after starting his own business in IT, he helped organize an online community for which he wrote and edited articles as managing editor, business and economics.
Here's a Calculator to Help You X. TL;DR Too Long; Didn't Read The percent yield is given by the actual yield of a particular reaction product divided by the maximum theoretical yield, both in grams, multiplied by 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.
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 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. Your answer will be a unit-less ratio. The actual yield was 29 grams, while the theoretical yield was Multiply by to convert to a percentage.
The answer is the percent yield. If in the reaction is below 32 of C2H6 and produces 44 grams of CO2, what is the percent yield? This is your theoretical yield based on the 32g of C2H6 you started with and the molar ratio between C2H6 and CO2 in your balanced equation. Not Helpful 0 Helpful 1. You can determine this by the coefficients in front of your desired reactant and product in your balanced equation.
Not Helpful 1 Helpful 1. How do I calculate the percentage yield when I'm only given the volume of the reactants? Not Helpful 6 Helpful Well water is composed of 3 atoms, 2 hydrogen and 1 oxygen. Not Helpful 7 Helpful What do I do with mols in different atoms when calculating the percentage yield? Actual yield divided by theoretical yield. Not Helpful 10 Helpful How do I calculate the limiting reactant when calculating the percent yield? Find the number of moles of the reactants and compare them.
The reactant with the least number of moles will be your limiting reactant. Actual yield is the mass that will be given to you after the experiment or in the exam question.
However, the actual yield will nearly always be given. Not Helpful 7 Helpful 1. Where can I find more examples that will help me solve specific problems that I need to calculate? Answer this question Flag as Include your email address to get a message when this question is answered. Already answered Not a question Bad question Other. Tips Some students confuse percent yield how much you obtained out of the total possible amount with percent error how far off an experimental result is from the expected result.
If you're subtracting the 2 yields, you're using the percent error formula instead. If you get wildly different results, check your units.
The discrepancy between the theoretical yield and the actual yield can be calculated using the percent yield, which uses this formula: To use this formula for percent yield, you need to make sure that your actual yield and theoretical yield are in the same units.
Since percent yield is a percentage, you would normally expect to have a percent yield between zero and If your percent yield is greater than , that probably means you .
To determine percent yield, divide the actual yield by the theoretical yield and multiply by For this example, use the equation: 82 grams of silver / 85 grams of silver x = 96 percent. This percentage tells you the efficiency of the chemical reaction, or how good the reaction is . You determine percent yield with the following formula: Lovely, but what is an actual yield, and what is a theoretical yield? An actual yield is, well, the amount of product actually produced by the reaction in a lab or as told to you in the chemistry problem.
So, ideally, grams of CaO should have been produced in this reaction. This is the theoretical yield. However, the problem tells us that only 15 grams were produced. 15 grams is the actual yield. It is now a simple matter to find percent yield. For example, if a company’s annual dividend is $ and the stock trades at $25, the dividend yield is 6 percent: $ / $25 =