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actual yield less than theoretical yield

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Question:Which of the following is NOT a reason why actual yield is less than theoretical yield? a) impure reactants present b)conservation of mass c)competing side reactions d)loss of product during purification

Answers:b) conservation of mass

Question:please elaborate more about this topic.i'm a little confuse...

Answers:There are several different issues involved. Some of these are practical issues and some are theoretical issues. The first is that the actual yield is based upon measurements and there is no such thing as a perfect measuring device. This can lead to errors in the measurements. Just as important is there is no such being as the perfect scientist to take and record those measurements. Human error often plays a role in the process of doing the experiment. These first two are the main reasons why in some rare instances, the actual yield is greater than 100%. Manipulations of physical materials are never perfect, especially transfers of reactants and products from one container to another. Filters always cause a loss. Next is the composition of the materials used in a chemical reaction. These are seldom 100% pure and often the amount of impurities are ignored in the calculations of the theoretical yield. This makes the theoretical yield higher than it should be. Time is also a factor. Experiments must be performed in a limited amount of time. Often all of the reactants are not allowed to react before the experiment is ended. Another thing to consider is that the equation used in the calculation of the theoretical yield is usually not the only reaction that can take place. It is usually the main reaction, but so called side reactions can also take place. This is especially true for complex molecules. The nature of the chemicals used can also be a factor if decomposition can take place. This is also true if one the reactants is highly unstable or can react with itself.

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Answers:Whenever energy changes form - from gravitational to electrical, from chemical to electrical, or from chemical to another form of chemical - some energy is always lost as heat. Therefore the transfer of energy is never 100%. Transferring energy form glucose to ATP is about 55% efficient.

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