help with a question!

[peanut273]

Ok..Stuck doing my lab report for uni and I wanted to know if anyone knows about using a spectrophotometer? I know what it is (used for the measuring the accurate characteristic absorbance of biological molecules) I get all that, the gamma rays, x-rays. All I'm wondering is if a substance is more concentrated will there be more absorption than a substance that is less concentrated.

HELLP!!!! x

[Buenchico]

OK, I admit that I'm out of my depth here. (My degree is in mathematics and, after 30 years, I've forgotten most of that subject. So I'm hardly qualified to post in response to your question).

However, simply Googling 'spectrophotometer concentration' suggests that the answer to your question is 'Yes'. For example, here's the first link produced by that search:
http://www.ahs.stpaul.k12.mn.us/jolson/chemist ry/spec.html

Chris

[peanut273]

Well Chris, Thanks with that!! Ok maybe you could teach me maths haha-I am a Forensic student and I find it really fascinating but I struggle with maths...whats you secrets lol.
no maths makes scence to me. Really x

[theprof]

Hmm. I've recently answered a whole series of questions on spectrophotometry on AB and you may find those answers useful - try searching for them using the search facility.

The answer to your final sentence depends upon the type of spectrophotometry being used. I'm surprised that given that you are at university, you're not sure of the type of spectrophotometry being used.

[terambulan]

Can't help, sorry....just borrowing this thread

[Teddio]

The degree of absorption is proportional to the concentration of the absorbing atom, molecule or ion in the medium. eg. the higher the concentration of ethanol in exhaled air, the greater the absorption of infrared radiation in the spectrophotometer .

[theprof]

This question revolves around the importance of the Beer-Lambert law in spectrophotometry.

Yes, it is true that if a compound is more concentrated, more light will be absorbed by the sample. In general, it's a linear relationship and can easily be demonstrated by dissolving increasing quantities of Crystal Violet for example in the solvent

[peanut273]

To the prof,

thanks-However i've never even heard of the spectrophotometer until University.

[theprof]

Well as far as not hearing about a spectrophotometer goes, I'm not really surprised given the less-demanding "A" levels nowadays. I left school having had the basic principals drummed into me in chemistry and physics in the sixth-form.

All the same, I would have thought that your tutors would have told you which type of spectrophotometer you were dealing with. This was what I was getting at.