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Determining the Concentration of a Solution: Beer’s Law

Determining the Concentration of a Solution: Beer’s Law. Chemistry 117. http:// en.wikipedia.org/wiki/File:Beer – Lambert_law_in_solution.JPG. Spectophotometry. Measures absorbance spectrum of a substance

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Determining the Concentration of a Solution: Beer’s Law

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  1. Determining the Concentration of a Solution: Beer’s Law Chemistry 117 http://en.wikipedia.org/wiki/File:Beer–Lambert_law_in_solution.JPG

  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 http://www.sarracenia.com/astronomy/remotesensing/physics050.html

  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. Beer-Lambert Law A= εbC Where A = absorbance, ε = molar extinction coefficient, b = path length (1cm), and C = concentration. A = – Log (T) (Note 0<T<1) T = I1/I0 http://teaching.shu.ac.uk/hwb/chemistry/tutorials/molspec/beers1.htm http://en.wikipedia.org/wiki/File:Beer_lambert.png

  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

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