1. Determining the Concentration of a Solution: Beer’s Law
Chemistry 117

2. Spectophotometry Measures absorbance spectrum of a substance
Must first measure the absorbance spectra VS wavelength. Maximum wavelength is used to calibrate and to be able to use beer’s law most effectively

3. Absorbance Compounds absorb UV or Visible light
100% transmittance means no light was absorbed
0% transmittance means all light was absorbed
Relationship between absorbance and transmittance is beer’s law

4. A = – Log (T) (Note 0<T<1)
Beer-Lambert Law
A= ε b C
Where A = absorbance, ε = molar extinction coefficient, b = path length (1cm), and C = concentration.
A = – Log (T) (Note 0<T<1)
T = I1/I0

5. Concentration and Transmittance
Transmittance is exponentially related to the concentration of the solution
We will plot Concentration Vs Absorbance with our spectrometer
Remember-
Dilution Equation: M1V1 = M2V2