2007-10-09 04:18:22 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Many years ago it was thought that when something burnt it got heavier, i.e. the yield was greater than 100%.
We now know that when something burns it is because it combines with oxygen and so does get heavyer.
Early scientists thought that the mistery chemical Flogeston was involved and that it had negative weight and was driven off when something burned.
2007-10-09 05:04:07 · answer #1 · answered by Anonymous · 0⤊ 1⤋
You cannot obtain a yield greater than 100%. To do a percent yield, you must calculate the predicted yield using stoichiometry and taking care to determine which of the species used is a potential limiting reagent. Then you carefully measure what mass of product you have as the experimental yield.
The equation is the experimental yield/predicted yield *100.
As a hint, per cent means per 100, you can never go above 100 with a "per cent".
Usually when this happens, an error was made in calculating the predicted yield (ignoring limiting reagents) or the product was weighed wet.
In response to some of the comments below:
Trust me, you cannot get greater than 100% yield. Matter is neither created nor destroyed. If you obtain a yield that is greater than the predicted (or theoretical) yield, it is contaminated (possibly with starting material), wet or simply not the product you want it to be. It just isn't possible in this case.
2007-10-09 11:25:19 · answer #2 · answered by householdbleach 2 · 0⤊ 0⤋
You can actually obtain yields greater than 100%....but the normally the extra yield is a function of contamination or instrument performance dependent on the type of method or analysis. Most instruments parameters will allow for +/- 25% on a low standard and +/- 15% on a mid/high standard. That would mean that a low standard could be 75-125% of the actual and mid to high standards can be 85-115%.
2007-10-09 11:26:40 · answer #3 · answered by carasmom 2 · 0⤊ 0⤋
It depends on the context. If you have a standard that you set as 100%, and something else you did gives you more than your standard, then you can get more than 100%. If you are the one doing the measurements, and after you are done you end up with more than 100% of the maximum theoretical yield, then you made some sort of measuring error. If it's money, and you invest and it grows, you would hope that you get more than you put in, but that's a different story. Be more specific for a more specific answer.
2007-10-09 11:25:51 · answer #4 · answered by archaeadoc 5 · 0⤊ 0⤋
A yield of what? It would help if you gave more specifics. In certain situations, greater than 100% yield is possible if reactions and/or synthesis is going on. Need to know more.
2007-10-09 11:23:22 · answer #5 · answered by Simonizer1218 7 · 0⤊ 1⤋
by re-defining terms such that, for instance, '100%' isn't really '100%'. otherwise, not.
2007-10-09 11:22:28 · answer #6 · answered by John R 7 · 0⤊ 0⤋