Concentration Of Iron And Chemical Substance

1486 Words Oct 20th, 2014 6 Pages
Concentration of Iron in an Unknown Substance
Jack Boswell
Experiment 5
Megan Otting and Dr. Caster
The objective of this lab was to determine the concentration of iron (Fe+2) in an unknown substance using a spectrophotometer. Spectrophotometry is a process that uses a sample solution to determine how much light a chemical substance absorbs by measuring the intensity of a beam of light passing through the solution. Every substance transmits light over a specific wavelength range, so spectrophotometry is often used to measure the amount of a known chemical in an unknown substance. White light, or sunlight, is shot through the opening slit of a cuvette containing the substance. The reflection of the substance by a diffraction grating, which uses a cam to separate white light into component wavelengths, then passes through the exit slit where it is received by a photoelectric cell, where it is converted to a measurable electric signal. Not all of the light is transmitted through the solution, however; some is absorbed into the solution by a certain chemical in it. The concentration of the chemical is directly related to the absorbed light and is shown through the Beers-Lambert law, often stated as A=εbc. In this equation, ε and b are constants of proportionality that allow A∝ c to be converted to a direct relationship. ε is known as molar absorptivity and remains constant while the same substance is analyzed. Cell thickness is represented by b and…
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