Spectrophotometry

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Author:
roobee
ID:
135283
Filename:
Spectrophotometry
Updated:
2012-02-14 17:36:05
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Spectrophotometry
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Description:
Biology Lab -Spectrophotometry
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  1. Different molecules absorb & reflect different wavelengths of light - therefore have different colors

    Chloryphyll reflects green light and absorbs other wavelengths.
    Spectrophotometry based on the principle that every different, atom, moleculs or chemical bond absorbs different wavelengths of light.
    Each Chemical has a unique pattern or "fingerprint" of various wavelenths that it absorbs or reflect
  2. Spectrophotomer- measures the amount of light absorbed /transmitted by a dissolved chemical. (non absorbed light as transmitted light)
    Can identify a chemical and its concentration by measuring absorbanc transmittance.

    Spectrophotometer separates white light into a spectrum of colors / wavelengths. It then directs a specifice wavelength of light at a tube containing a solution it is trying to measure. Light is either absorbed by the dissolved substance or transmitted through the solution & exits the sample.
  3. Spectrophotometry compares the amount of light exiting the tube (transmitted light) with the amount entering the tube and calculats transmittance
    more solute= lower transmittance
    light absorbed
    more solute = higher the absorbance
  4. Blank tube- cuvette
    contains only the solvent used to calibrate the spectrophotometer for solution used with solute.
  5. Relationship between concentration & absorption is linear (directly proportional)

    Standard curve- chemicals concentration vs it's absorption of a wavelenth of light is called a standard curve. straight line
  6. Any light transmitted through the sample exits the sample on the opposite side & is focused on a photodetector that converts light energy to electrical energy.
    Amount of electricity produced by the photo detector is proportional to the amount of transmitted light.
    more light transmitted=more electricity producedd

    Meter- measures electrical current- scale of absorbance.
  7. Absorbance- amount of radiation retained by the sample.

    Absorbance values are directly proportional to the concentration of the the substance in the solution.

    Increase in absorbance=increase in concentration -- it is a direct relationship.
    used cobalt chloride & chloryphyll for the experiment

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