  Examining how much light is absorbed by a compound’s sample at various wavelengths  Spectrum peaks—  Indicates the wavelengths associated with electrons’ energies in a compound (how much energy is absorbed)  Mainly used to determine a sample’s concentration when unknown UV Spectroscopy

  Relates concentration and absorbance  Enables a sample’s concentration to be determined based on its absorbance value  A= ε bc  A= absorbance  ε = molar absorptivity (molarity -1 centimeters -1 )  b = path length  c = concentration (molarity, M) Beer’s Law

  How far electromagnetic radiation must travel through a sample  Unit—centimeters (cm)  Increased length, radiation hits more molecules and leads to higher absorbance Path Length (b)

  Analyzing Absorbance Data  Form a standard curve based on absorbance measurements of standard solutions with KNOWN concentration at a specific wavelength  Plot absorbance vs. concentration graph— standard Beer’s law plot  Generates a straight line  Slope of line = Δ A / Δ C  eb = constant SO can find concentration of unknown sample with absorbance measurement. SO WHAT?

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