Spetctophotometry (11.5).docx

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UNIVERSITY OF BALAMAND Faculty of Sciences Department of Chemistry Basic Chemistry Laboratory Names: Lara Frangieh ID: A0810408 Anthony Dahdah ID: A0810784 Experiment Title: Spectrophotometry Experiment Week: Week 6 Date: 12/11/09 Submitted to: Dr. Robin Taleb 1
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Introduction: The concentration of a colored constituent can be determined by measurement of the relative intensity of a light ray before passage (incident light) and after passage (transmitted light) through a solution which is placed inside a cuvette. The percentage of the incident light, which is finally transmitted after passing through the solution, is called the percent transmittance. Any light not transmitted is absorbed by the solution. This process takes place in the spectrum. It can be shown that the absorbance of a solution is proportional to the concentration of the absorbing substance: A=a b c Where: “A” is the absorbance “a” is a constant called absorbtivity or extinction co-efficient(L/mol.cm) “b” is the distance or depth of solution through which light must pass which is equal to 1 cm “c” is the concentration of absorbing species (mol/L) For a series of solution of several concentrations, the plot of “A” vs. “c” will be linear. This relationship is called the Beer-Lambert Law. Such analysis is performed at a wavelength called the maximum absorbance wavelength. The aims of the experiment were: To determine the maximum absorbance wavelength using a NO Cr ( ¿¿ 3 ) 3 ¿ solution (0.05M) 2
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To measure the absorbance of 5 solutions of NO Cr ( ¿¿ 3 ) 3 ¿ (0.01, 0.02, 0.03, 0.04 and 0.05 Molar) To record the readings, and to plot “A” vs. “C” To determine the concentration of two unknown sample of NO Cr ( ¿¿ 3 ) 3 ¿ from Beer’s law graph To prepare 5 solutions (A,B,C,D, and E) of KMn O 4 To measure the absorbance of each solution, and to draw the plot of “A” vs.“C” To determine the concentration of an unknown sample of KMn O 4 solution Used equipments: 50 ml, 100 ml, and 200 ml volumetric flaks 20 ml, 25 ml, and 50 ml pipette 250 ml beaker Spectrum Dropper Used chemicals: Solution of NO Cr ( ¿¿ 3 ) 3 ¿ (0.01, 0.02, 0.03, 0.04, and 0.05 Molar) Solution of KMn O 4 (4x 10 3 M) Solution of H 2 S O
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  • Winter '15
  • Amir Alimohammad
  • Chemistry, cuvette, Department of Chemistry, University of Balamand

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