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Experiment 34: An Equilibrium Constant Kaitlyn Chomko Tiernan Noll and Saajan Vemala Chem 1310/DA8 Professor Richard H. Perry Brandon 02/23/18
Hypothesis: If the volumes and molar concentrations of NaSCN of Fe(NO 3 ) 3 are varied between solutions containing HNO 3 the absorbance and transmittance between the solutions will be different. The more NaSCN in a solution, the lower the percent absorbance. A calibration curve of absorbance versus [FeNCS 2+ ] can be used to determine the equilibrium molar concentration of [FeNCS 2+ ]. From there, the equilibrium constant is calculated by using this equation: K c = FeNCS 2 + ¿ ¿ Fe 3 + ¿ ¿ SCN ¿ ¿ ¿ ¿ Materials and Methods: Source: Please refer to experiment 34: An Equilibrium Constant in Laboratory Manual for Principles of General Chemistry by J.A Beran on page 283 There were no deviations in this experiment Data: II Lab/excel ex- 34.xlsx
0.00E+00 5.00E-05 1.00E-04 1.50E-04 2.00E-04 2.50E-04 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 f(x) = 3818.57x - 0.01 Calibration Curve [FeNCS2+] (mol/L) Absorbance, A [FeNCS 2+ ] ( mol/L ) Absorbance , A 0.00E+00 0.00 4.00E-05 0.126 8.00E-05 0.302 1.20E-04 0.432 1.60E-04 0.568 2.00E-04 0.778
Calculations: E11. Moles of SCN - (mol) Moles of SCN - (mol) = Molarity NaSCN (M) • Volume NaSCN (L) 1.00E-06 = .001 • .001 E12. [SCN - ] (25 mL) ( mol/L ) [SCN - ] ( mol/L ) = MolesSCN ¿ .025 ¿ 4.00E-05 = 1.00E-06 .025 E.13 [FeNCS 2+ ] ( mol/L ) [FeNCS 2+ ] ( mol/L ) = [SCN - ] (25 mL) ( mol/L ) 4.00E-05 = 4.00E-05 C.26 Moles of Fe 3+

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