# Can the Percent yield be more than 100%? Why?

Asked by lanahopple (455) January 18th, 2010
Observing members: 0 Composing members: 0

No, I will not stoop to doing your homework in exchange for lurve.

lilikoi (10064)

well, percent yield in chemistry is actual yield divided by theoretical yield so if your theoretical yield is below 100% then conceivably you could have a greater than 100% yield.

wonderingwhy (10775)

Okay thanks! I wasn’t quite sure… now off to the hard problems…. sigh :/

lanahopple (455)

via Wikipedia

The ideal or theoretical yield of a chemical reaction would be 100%, a value that is impossible to achieve due to limitations in measurement accuracy. According to Vogel’s Textbook of Practical Organic Chemistry, yields around 100% are called quantitative, yields above about 90% are called excellent, yields above about 80% very good, yields above about 70% are called good, yields below about 50% are called fair, yields below about 40% are called poor. Yields may appear to be above 100% when products are impure. Purification steps always lower the yield and the reported yields usually refer to the yield of the final purified product.

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So, yes, the percent yield can be more than 100%. It usually means you did something wrong, though.

robmandu (21242)

oh. looks like all my calculations are wrong. kidding haha. okay thanks for the help

lanahopple (455)

you fucked up, ianahopple.

back to the beginning.

warribbons (606)

Funny :(
haha

lanahopple (455)

No, it cannot be. If you have a chemical reaction where you get more than you origanally put in, (which would be an answer of over 100%) something else was added to that chemical reaction somewhere along the way. If you start with 4 and add 3, you won’t come out with 9 will you? Chemical reactions work the same way. It may be possible for an element not to be included in the original equation that you are working with, in which case you would indeed end up with a number of ever 100%. Hope this is more helpful!

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