CHE 315: UV-Visible Spectrophotometry and Colorimetry
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Questions and Answers

What type of lamps are used in UV-Visible spectrophotometry?

  • Deuterium and tungsten filament (correct)
  • Mercury and xenon
  • Fluorescent and incandescent
  • Halogen and LED

    • In which wavelength range does colorimetry mainly work?

  • 200-800 nm
  • 400-700 nm (correct)
  • 100-500 nm
  • 700-1000 nm

    • What is the purpose of a monochromator in a UV-Visible spectrophotometer?

  • To analyze solid samples
  • To emit visible light
  • To separate polychromatic light into monochromatic light (correct)
  • To generate UV light

    • Why are colorimeters considered cheap and easy to operate?

    <p>Due to the use of simple narrow band filters</p> Signup and view all the answers

    Which region of the electromagnetic spectrum do UV-visible spectrophotometry and colorimetry cover?

    <p>UV to visible region</p> Signup and view all the answers

    Why are UV-Visible spectrometers more expensive compared to colorimeters?

    <p>They are equipped with two different lamps</p> Signup and view all the answers

    What is the wavelength of maximum absorption known as?

    <p>Lambda max (λmax)</p> Signup and view all the answers

    In the UV-visible spectrum of lycopene, what is the lambda max value?

    <p>471 nm</p> Signup and view all the answers

    What does the detector in a UV/VIS spectrophotometer or colorimeter measure?

    <p>Intensity of transmitted light</p> Signup and view all the answers

    What is the ratio between the intensities I / I0 defined as?

    <p>Transmittance T</p> Signup and view all the answers

    Which law is applied for quantification based on the absorptivity of pure compounds?

    <p>Beer-Lambert Law</p> Signup and view all the answers

    What term refers to the attenuation of transmitted light by sample molecules in solution?

    <p>''Transmittance T''</p> Signup and view all the answers

    What can happen if the molecules in a solution are at high concentrations?

    <p>They aggregate, leading to incorrect readings</p> Signup and view all the answers

    Why is it essential for the solution not to contain molecules that emit fluorescence when excited?

    <p>To avoid erroneous readings</p> Signup and view all the answers

    What is necessary for determining the concentration of an unknown sample using UV/VIS spectroscopy?

    <p>Creating a calibration curve</p> Signup and view all the answers

    How is a calibration line obtained for UV/VIS spectroscopy analysis?

    <p>Linear regression of absorbance values</p> Signup and view all the answers

    What does the Lambert-Beer Law form the basis for in UV/VIS spectroscopy?

    <p>Determining unknown sample concentrations</p> Signup and view all the answers

    What purpose do UV/VIS spectra serve in identifying components in a sample solution?

    <p>Identifying sample components</p> Signup and view all the answers

    What allows specific compounds to be identified in UV/VIS spectroscopy?

    <p>Position and profile of the absorption peaks</p> Signup and view all the answers

    How is the blank in UV/VIS spectroscopy typically measured?

    <p>Intensity of light transmitted through the solvent</p> Signup and view all the answers

    What is the purpose of measuring the absorbance value of a peak in UV/VIS spectroscopy?

    <p>To calculate the sample concentration</p> Signup and view all the answers

    Why is a blank measurement necessary in UV/VIS spectroscopy?

    <p>To measure the intensity of transmitted light through the solvent</p> Signup and view all the answers

    In which market segments is UV/VIS spectroscopy commonly used as a quantitative analytical technique?

    <p>Water Testing, Food and Beverages, Pharmaceutical, Chemical and Biotech Industry</p> Signup and view all the answers

    What is added to a cuvette for blank measurement in UV/VIS spectroscopy?

    <p>Solvent like water or alcohol</p> Signup and view all the answers

    How is absorbance calculated in a spectrophotometer?

    <p>By dividing the transmitted intensity of the sample solution by the corresponding values of the blank</p> Signup and view all the answers

    What is the purpose of using absorbance values for standard solutions in spectrophotometry?

    <p>To plot the calibration curve</p> Signup and view all the answers

    Why is it important to measure absorbance in a spectrophotometer?

    <p>To quantify the amount of light absorbed by sample molecules</p> Signup and view all the answers

    What role do standard solutions play in UV/VIS spectrophotometric analysis?

    <p>They aid in plotting calibration curves</p> Signup and view all the answers

    Why is it necessary to extrapolate concentrations from a calibration curve in spectrophotometry?

    <p>To quantify unknown sample concentrations</p> Signup and view all the answers

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