Determination of an Equilibrium Constant Lab

# Determination of an Equilibrium Constant Lab - Stephanie...

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Stephanie Warner Chem 153 Shidong Chu 9 December 2005 Determination of an Equilibrium Constant Purpose: To determine the equilibrium concentrations of all species involved in a reaction, so that that equilibrium constants for the unknowns can be calculated. Calculations: a) [Fe 3+ ] for Unknown Solution 2 = (1.30mL/10.0mL)(6.00e-2 M) = 7.8e-3 M b) [FeSCN 2+ ] from calibration plot for solution 1 Absorbance = .285 .285 = 4247.18012x + 0.012775 .272225 = 4247.18012x 6.4e-5 = x [FeSCN 2+ ] = x [FeSCN 2+ ] = 6.4e-5 c) K from ICE table for solution 3 K = [FeSCN 2+ ] / ([Fe 3+] [ SCN - ]) K = [1.2e-4M / (1.3e-2 M) (5.5e-5 M)] Unknown Soln. No. % T Absorbance [Fe(SCN) 2+ ] [Fe 3+ ] [SCN - ] K 1 51.9% .285 6.4e-5 M 4.1e-3 M 1.1e-4 1.4e2 2 38.0% .420 9.6e-5 M 7.7e-3 M 7.9e-5 M 1.5e2 3 29.9% .524 1.2e-4 M 1.3e-2 M 5.5e-5 M 1.6e2 Questions: 1) All of my values for K are 10^2. If you average these I would consider the equilibrium constant to be large. The formation of the FeSCN 2+ complex is favored under the conditions of our experiment because the values of our

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Determination of an Equilibrium Constant Lab - Stephanie...

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