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Determining the Concentration of a Solution: Beer’s Law
Chemistry 117
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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
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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
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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
%2b(note%2b0_t_1).jpg "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/I")
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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
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