[swissguy604]

Hi I am having quite a bit of difficulty with this calculation, what I have so far is

Eugenol: 0.0061 g, in 100 ml solution make 0.00037149 M solution with a lambda max of 1.101

Oil of cloves: 0.0076 g, in 100 ml solution ( needs to be determined) with a lambda max of 1.900

so I understand A1/A2=C1/C2, I also have to adjust the ratio for the difference in mass between the two which I expect is ~80%. After doing this I end up with a value of 0.000513 M for the concentration of eugenol in the oil of cloves sample. Which is higher than what I expect the theoretical limit of 0.000462 M ( 0.0076/164.2) is. Ive been playing around with the numbers and I just can't seem to get it.

I know there suppose to be ~90% eugenol in oil of cloves and the only way I get somewhere close to that is if I divide the theoretical value by the experimentally determined one and multiply by 100, but that doesn't sound right to me and I am totally unsure If I made a mechanical error along the way because from what ive found scouring the internet, is that my values are not far off from similar weight to lambda max values.
Any help would be greatly appreciated.


I made the mistake of originally posting this in the other science questions and im not sure how to switch them over, apologies.

[Borek]

Eugenol: 0.0061 g, in 100 ml solution make 0.00037149 M solution with a lambda max of 1.101

Lambda max? Or absorbance at lambda max?

so I understand A1/A2=C1/C2

Yes. To some extent it doesn't even matter what units the concentration is expressed in, in your case best approach is to use mg/L or something like that. Molarities are OK, they just add additional steps of converting moles to grams back and again, which is unnecessary.

Sadly numbers you have listed don't add up, as it looks as if your oil of cloves contained well over 100% of eugenol.

[swissguy604]

Thanks Borek

Sorry, yes I did mean absorbance at lambda max.

So I am on the right track with the use if formula and adjusting for the difference in mass? I saw a previous thread regarding this same experiment

http://www.chemicalforums.com/index.php?topic=45223.0

Their values for absorbance at lambda max and concentration would also result in a value of eugenol over 100%. Is there any other way to approach this problem? or is there a strong likelihood that I made a mistake in the experiment along the way?

Thanks again.

[Borek]

So I am on the right track with the use if formula

Yes.

and adjusting for the difference in mass?

Not sure I understand what you mean. All you can do is to calculate mass of eugenol in the oil of cloves sample (from determined concentration and known volume). Then you can compare that with the mass of the oil of cloves.

or is there a strong likelihood that I made a mistake in the experiment along the way?

That's my bet, looks like the experiment is rather straightforward and calculations simple - unless you have omitted some important part about the procedure followed.

[swissguy604]

Thanks again Borek,

With regards to the mass adjustment, in my Lab Manual the exact comment that is made is

"The ratio of peak heights corresponds to the amount of eugenol in the sample. The ratio must also be adjusted for the differences in masses of the two samples."

I haven't been able to find anything that makes sense to me regarding that. I used % difference between the two masses in an attempt to try and make sense of it, but im not 100% sure if thats the correct application.

[Borek]

"The ratio of peak heights corresponds to the amount of eugenol in the sample. The ratio must also be adjusted for the differences in masses of the two samples."

That just means you can't use ratio of absorbances directly to find the answer, you have to follow the absorbance -> concentration -> mass -> percentage path.

[swissguy604]

Thanks a lot for the help Borek, I really appreciate it.