[Dogworld]

Hello. I have a problem that I am trying to complete a write-up for, but want to ensure I am heading in the right direction. Basically, The problem states that there are two compounds, both with the same empirical and molecular formula; however each has a different spectral absorbance. My thought is that this is related to the difference in weight of the compounds. Am I thinking correctly? Thanks.

[Corribus]

If two compounds have the same molecular formula, how can they have different molecular weights?  And even if they did, why would this explicitly account for a different spectral absorbance?

Why don't you reproduce the problem here exactly, rather than paraphrasing?

[Big-Daddy]

Clearly the difference will be due to isomerism of some kind, which is completely to be expected - different isomers will of course absorb different amounts of light at a certain wavelength.

The exact case is up to your problem.

[Corribus]

Clearly the difference will be due to isomerism of some kind, which is completely to be expected - different isomers will of course absorb different amounts of light at a certain wavelength.

Not necessarily.

[curiouscat]

Clearly the difference will be due to isomerism of some kind, which is completely to be expected - different isomers will of course absorb different amounts of light at a certain wavelength.

Not necessarily.

different isomers will mayof course absorb different amounts of light

[Big-Daddy]

Not necessarily.

Ok, you know what I mean.  What about isotopomers, do they ever have different absorbance coefficients at the same wavelength?

[Corribus]

Depends on the spectral range. UV-visible? In most cases, no.  IR or microwave? Yes, frequently, of course.