Experiment 17 Lab Report - William Seo Experiment 17:...

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William Seo Experiment 17: Chemical Equilibrium and Beer’s Law January 31, 2012 CHEM 1212k A02 I did not share this lab report with anyone after lab was finished.
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Data/Results Part A: Beer’s Law Plot Test Tube Diluted Fe 3+ (mL) Stock 0.50 M KSCN (mL) Stock 0.1 M HNO 3 (mL) Absorbanc e at 450 nm [Fe(SCN) 3+ ] (M) 1 1.0 5.0 4.0 1.177 1.0x10 -5 2 2.0 5.0 3.0 1.027 2.0x10 -5 3 3.0 5.0 2.0 0.759 3.0x10 -5 4 4.0 5.0 1.0 0.423 4.0x10 -5 5 5.0 5.0 0.0 0.091 5.0x10 -5 Molar absorptivity ( ε ): The slope of the linear trend line is approximately equivalent to molar absorptivity. To find the units, look at the equation A = ε bc; since A is dimensionless, molar absorptivity must have the units equal to that of the inverse of the units of “b” and “c.” The units for “b” is cm and the units for “c” is mol/L; therefore, the units of “ ε ” is . ε = . The molar absorptivity should be a positive value because more light should allowed to pass through the test tube when there are lesser concentrations of Fe(NO 3 ) 3 ; however, because more light passed through when there was supposedly more Fe(NO 3 ) 3 , there was an error while making the solution (it was discovered later than instead of using stock 0.0025M Fe 3+ solution, the diluted Fe 3+ solution was used in test tubes 6-15). The red equation closer to the top of the graph shows the molar absorptivity if the experiment was conducted properly (intercept at y=0). In order to be consistent, the subsequent measurements were done with respect to the incorrect equation. Sample calculations:
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Part B: Determining the Equilibrium Constant Test Tube 0.0025 M Fe 3+ (mL) 0.0025 M SCN - (mL) 0.1 M HNO 3 (mL) Total (mL) Absorbance at 450 nm 6 1.0 1.0 5.0 7.0 0.680 7 1.0 1.5 4.5 7.0 0.745 8 1.0 2.0 4.0 7.0 1.883 9 1.0 2.5 3.5 7.0 1.918 10 1.0 3.0 3.0 7.0 1.067 11 2.0 1.0 4.0 7.0 0.499 12 2.0 1.5 3.5 7.0 0.282 13 2.0 2.0 3.0 7.0 0.752 14 2.0 2.5 2.5 7.0 0.543 15 2.0 3.0 2.0 7.0 0.482 Test Tube [Fe 3+ ] initial (M) [SCN - ] initia l (M) [Fe(SCN) 2+ ] (M) [Fe 3+ ] eq. (M)
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This note was uploaded on 02/26/2012 for the course CHBE 2100 taught by Professor Staff during the Spring '08 term at Georgia Institute of Technology.

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Experiment 17 Lab Report - William Seo Experiment 17:...

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