 Custom Search Beers-Lambert Law
Use this for solutions with color...transition elements (the darker it is the more concentrated)
BEER’S LAW To measure the concentration of a solution over time, a device called a spectrophotometer can be used in some situations. A spectrophotometer measures the amount of light at a given wavelength that is absorbed by a solution. If a solution changes color as the reaction progresses, the amount of light that is absorbed will change. Absorbance can be calculated using Beer’s Law: Beer’s Law A = abc
A = absorbance a = molar absorptivity, a constant that depends on the solution b = path length, the distance the light is traveling through the solution c = concentration of the solution
(NOTE you get 3 of the 4 variables.....solve for the 4th) As molar absorptivity and path length are constants when using a spectrophotometer, Beer’s Law is often interpreted as a direct relationship between absorbance and the concentration of the solution. Beer’s Law is most effective with solutions that visibly change color over the course of a reaction, but if a spectrophotometer that emits light in the ultraviolet region is used, Beer’s Law can be used to determine the concentrations of reactants in solutions that are invisible to the human eye.
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