Video Transcript
Which of the following statements best describes the theoretical yield? (A) The theoretical yield is the same as the actual yield multiplied by 100. (B) The theoretical yield is the maximum amount of product that can be formed from the given amounts of reactants. (C) the theoretical yield is the amount of product that is obtained experimentally from the reaction. Or (D) the theoretical yield is the result of adding the percentage yield to the actual yield.
The yield of a chemical reaction is the amount of product made. We can hypothesize how much product will be produced from the amount of reactants. For example, if we had 50 grams of reactants, we might expect 50 grams of product to form. This would only occur if all of the reactants were converted into product. Generally speaking, this is not possible as there is likely to be product loss during experimental procedure, from transferring substances from one container to another or through filtration or the reaction may not have completed, in which case there may be some starting material in the product.
There could have been unwanted side reactions, or there could have been impurities in the reactants. So, the mass calculated for them would be incorrect. That would make the predicted yield incorrect, or the reaction could be reversible. So, some of the product may reform the starting material, preventing a complete reaction. So, for this example, achieving a yield of 50 grams is very unlikely. In reality, it’s much more likely that less than 50 grams of product is formed.
Let’s say, for example, that 34 grams of product was actually measured. This would be the actual yield where the actual yield is the amount of product that is obtained from carrying out a chemical reaction. And in this example, the 50 grams of product would be the theoretical yield, where the theoretical yield is the maximum amount of product that can be formed from the given amounts of reactants. From this, we can determine that (B) is the correct answer. But to make sure that our answer is correct, let’s look at the other options.
Option (A) states that the theoretical yield is the same as the actual yield multiplied by 100. So using the example, that would give a yield of 3400 grams. This doesn’t sound very plausible given that there were 50 grams of reactants. Also, the theoretical yield is not based on the actual yield; it’s based on the reactants. So, we know that option (A) cannot be the answer to this question. Option (C) states that the theoretical yield is the amount of product that is obtained experimentally from the reaction, but we know this to be the definition of the actual yield, not to the theoretical yield. Thus, option (C) cannot be the answer to this question either.
Option (D) states that the theoretical yield is the result of adding the percentage yield to the actual yield. The percentage yield is calculated by dividing the actual yield by the theoretical yield and multiplying by 100 percent. If we were to rearrange this equation, putting the theoretical yield as the subject, then the theoretical yield equals the actual yield divided by the percentage yield multiplied by 100 percent. It is not calculated by adding the percentage yield to the actual yield. So, we can be sure that option (D) is not the answer.
So, the answer to the question “Which of the following statements best describes the theoretical yield?” is (B). The theoretical yield is the maximum amount of product that can be formed from the given amounts of reactants.
