Question Video: Calculating the Percentage Yield for a General Reaction | Nagwa Question Video: Calculating the Percentage Yield for a General Reaction | Nagwa

Question Video: Calculating the Percentage Yield for a General Reaction Chemistry • First Year of Secondary School

A student isolated 25 g of a compound following a procedure that would theoretically yield 81 g. What was its percent yield? Give your answer to 1 decimal place.

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Video Transcript

A student isolated 25 grams of a compound following a procedure that would theoretically yield 81 grams. What was its percent yield? Give your answer to one decimal place.

The question tells us what the procedure would theoretically yield. The theoretical yield of a reaction is the maximum amount of product that can be formed from the given amounts of reactants. Generally speaking, the theoretical yield cannot be obtained in practice. There are multiple reasons why. There could be impurities in the reactants, meaning the mass of reactants is inaccurate. Thus, the theoretical yield would be inaccurate. Unwanted side reactions could occur, or the reaction may not have completed. Some of the material may have been lost during experimental procedure from transferring substances from one container to another or during filtration, for example. Or the reaction may be reversible, so some of the product may reform the starting material, preventing a complete reaction.

The question asks us for the percent yield. The percent yield, or percentage yield, is the actual yield divided by the theoretical yield multiplied by 100 percent, where the actual yield is the amount of product that is obtained from carrying out a chemical reaction. The question tells us that 25 grams of product was isolated. This is the actual amount of product obtained, so it is the actual yield. The question also tells us that the procedure would theoretically yield 81 grams. So the theoretical yield is 81 grams.

We now need to multiply the 25 grams over 81 grams by 100 percent. The gram units cancel, leaving us with an answer of 30.864 percent. The question asks for the answer to be given to one decimal place. 30.864 to one decimal place is 30.9. So the answer to the question “What was its percent yield?” is 30.9 percent.

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