### Percent yield

Posted:

**Mon Oct 01, 2018 3:02 pm**when finding the percent yield, is the actual yield always given to you?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=13&t=32762

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Posted: **Mon Oct 01, 2018 3:02 pm**

when finding the percent yield, is the actual yield always given to you?

Posted: **Mon Oct 01, 2018 3:08 pm**

Yes, you will always be giving either the actual yield itself, or other information from which you have to calculate actual yield. By definition, you can't calculate percent yield without the actual yield.

Posted: **Mon Oct 01, 2018 3:17 pm**

It should either be given or information should be given for you to find out on your own but you need both the actual and theoretical values to find the percent yield.

Posted: **Mon Oct 01, 2018 3:57 pm**

The theoretical yield is found once you have done the limiting reagent calculations. So once you know which is the limiting reagent the theoretical yield is calculated by multiplying molar mass and number of moles of whichever product you are solving for.

Posted: **Mon Oct 01, 2018 4:15 pm**

One way I use to remember the formula for percent yield is that I know percent yield will always be under 100%. Therefore, the smaller value (actual yield) will always be divided by the larger value (theoretical yield). By using this, we will always know that the equation for percent yield = actual/theoretical

Posted: **Mon Oct 01, 2018 4:27 pm**

In an ideal scenario the actual value would be 100%, but because of side reactions and experimental error, the theoretical is always greater than the actual yield.

Posted: **Mon Oct 01, 2018 5:00 pm**

Reese - Dis 1G wrote:when finding the percent yield, is the actual yield always given to you?

Since percent yield= actual yield/theoretical yield, I would have to assume that you are always given the actual yield because you are only able to calculate the theoretical yield as the actual yield is almost always different due to error. In a problem where you must find percent yield, yes the actual yield will be given.

Posted: **Mon Oct 01, 2018 8:35 pm**

The actual percent yield would be given like how molar mass of a compound would need to be given in order to further advance calculations. :)

Posted: **Mon Oct 01, 2018 9:47 pm**

In the majority of questions, the actual yield will be given to you, so you won't have to calculated yourself. Instead you might be asked to calculate the theoretical yield instead.

Posted: **Wed Oct 03, 2018 5:46 pm**

Actual yield should be given and if it is not then you cannot determine percent yield . The theoretical yield (what you'd calculate) is what would be produced in a perfect reaction with nothing lost (due to heat/ measuring errors/ etc.). The actual yield is usually an experimental value and therefore the higher your percent yield, the "better" you have conducted your experiment.

Posted: **Wed Oct 03, 2018 10:52 pm**

Almost always, the actual yield will be given to you. You then will usually have to calculate the theoretical yield and divide the actual yield by the theoretical yield to get the percent yield.