Beer's Law

So here we're going to say that beer's law represents a theoretical model that forms a correlation between the substance absorbent and its concentration. See here it's given by the formula that a equals epsilon times C. Times L. Here again A represents our absorbent. E. U. Represents our moller absorptive. Itty Here, this is just a physical characteristic of a compound. It usually ranges from values of 0-15,000. See here represents our concentration. Remember concentration is synonymous with polarity. So units are usually moles per liter. El he represents the path length or the width of the queue vet within the spectral for to meter here. So this would be path length which is the width of the queue vet in centimeters. Then we're gonna say here that absorbency equals log of I sub not divided by I. So I submit represents the intensity of the reference beam and I hear represents the intensity of the sample beam. Alright, so here we're gonna talk about this uh spectral for Tom Attar. Alright, so if we take a look here, we're gonna say the application of beers laws can be a beer's law can be seen with the use of a UV viz so ultraviolet and visible light spectrum for tom Attar with a conjugated compound. Now when we talk about a conjugated compound, it just means it has alternating double and single bonds. A great example of that would be 1 3 but a dying. So it would look like this. So this would be a conjugated system or conjugated compound because it's double bond single bond double bond. Now, basically the way we have this spectral for tom Attar is basically, it's gonna irradiate a sample with wavelengths of light usually ranging from so light ranging from 200 - 800 nm here. The light source, which can come from two different types of lamps. You can have a tungsten lamp with some other type of metal lamp. And what happens here is it shoots a beam of light which is reflected here on this monochrome mater monochrome better. Um which then gets split so you can get split and we're gonna say here, it gets split into two beams and one beam is gonna pass through a q vet containing the organic compound dissolved in some solvent. While the other beam, which is the reference beam is going to pass through a que vete containing only the solvent. Alright, so here this is my reference. So this one has only solvent. And then here this is the sample. So that one's gonna have the organic compound that is dissolved in the solvent. And then what's gonna happen here, the spectral for to meter, basically it's going to compare the two intensities of the beams at a particular wavelength and basically it's gonna plot those results to show the absorbent as a function of wavelength here. It's in terms of wavelength, in terms of nanometers. And we're going to say here, it gives us this image here of a particular compound. We're gonna say this image here is your absorbent spectrum and it just uses computer software in order to generate that absorbent spectrum. Now here we're gonna say when a conjugated system like peter dying is irradiated with UV light. A pi bond can be promoted to a higher energy level and produce UV vis absorption spectrum below. So here this would be the UV vis spectrum of of dying. Well actually have ice cream not dying. We used ice cream in this one actually. And all that's really happening. If we look at you're dying, we'd say that beauty dying has four carbons that are all sp two hybridized. Remember if your sp two hybridized, that means you're connected to three groups, three elements in this case, each carbon. Because if we branch out the hydrogen that they're each connected to. Just to show the real connections. Okay, so each carbon is connected to three things. So we have so we have four carbons that are SP two hybridized. So that gives us a number of molecular orbital's. And then we're going to say that this molecular orbital will be sy one side to side three and C four. We're gonna say we have two pi bonds. This one's a pi bond pi bonds just a double bond and this one's a pi bond in total, there's four electrons within those two pi bonds. So we plot those electrons here on the ground state molecular orbital diagram that we've constructed. So one electron up one electron down, one electron up one electron down. This would represent the ground state of my buddha dying compound. When we irradiated with UV light, we're able to promote one of the electrons up to a higher energy state. So all that happens here is one of these electrons is just gonna jump up to a higher energy state. So there it goes right there. So this shows us how the electron jumps up to a higher energy state in the absorption of UV light. And we're talking about the UV spectrometer were basically looking to see this excitation of an electron. And then we compared to the reference que vet and seeing from these two what my absorbent spectrum could potentially look like with the right software used. Okay, so just remember beers lost. Just a way of us trying to form a connection between absorb ints and the concentration of our compound. Go on to the next page and see some calculations that are pretty typical when it comes to beer's law. And this idea of the connection between absorbent and concentration