Presentation on theme: "Unit 2 Spectroscopy and Beers Law. This is a spectrophotometer. Spec-20D +"— Presentation transcript:
Unit 2 Spectroscopy and Beers Law
This is a spectrophotometer. Spec-20D +
Spectrophotometers work similarly to this device. Vernier Colorimeter
The spectrophotometer is meant to measure the absorbance of light in a sample.
What is absorbance? A measure of how much light (or electromagnetic radiation) does NOT go through the sample. This means the sample is typically colored.
In the case of the Spec-20D+, or a colorimeter, the portion of the electromagnetic spectrum must be…
the visible light wavelengths. 700 nm 400 nm
So, what is Beers Law? a measurement of the amount of absorption at the wavelength of greatest absorption can determine the concentration of the absorbing species present A = d c A = Absorbance = characteristic absorptivity of the strength of the species d = thickness of the sample c = concentration Create a single number that is constant, k.
So, what is Beers Law? A = k c This shows that absorbance (A) is directly proportional to concentration (c). Absorbance Concentration This relationship will allow you to measure the absorbance of known concentrations and plot them. You will then measure the absorbance of an unknown concentration. Your graph will allow to interpolate that absorbance to determine the samples concentration.