Initial Change Equilibrium Solution Concentration Absorbance Fe3+ SCN- FeSCN²+ 0.00 Table 1: Standard Solutions for FeSCN2+ Beer's Law Plot Solution [Fe3+] [SCN] S1 (blank) 4.0 x 10-2 M 0.0 M S2 4.0 x 10-2 M 4.0 x 10-5 M S3 4.0 x 10-2 M 8.0 x 10-5 M S4 4.0 x 10-2 M 12.0 x 10-5 M S5 4.0 x 10-2 M 16.0 x 10-5 M S6 4.0 x 10-2 M 20.0 x 10-5 M Solution Volume in mL of 0.00200 M Fe(NO3)3 Table 2: Volumes for Unknown Equilibrium Solutions Volume in mL of 0.10 M HNO3 Volume in mL of 0.00200 M NaSCN E1 (blank) 5.00 0.00 5.00 E2 5.00 1.00 4.00 E3 5.00 2.00 3.00 E4 5.00 3.00 2.00 E5 5.00 4.00 1.00 E6 5.00 5.00 0.00

Absorbance values: 0, 0.127, 0.282, 0.432, 0.576, and 0.710. Plus the heat of 0.710 is 0.583 in a warm bath of 59.6 C. 

y = mx +b which is "y= 3605x- 0.006"
• Y = absorbance, m = slope, x = concentration, b = y-intercept
1. Determine the unknown concentration of your mixtures from your measured absorbances
• Solve the best fit line equation for x for each equilibrium mixture (E1-E6)
3. Set up ICE tables for each E mixture to find [Fe3+] and [SCN-] at
equilibrium for each
• Use the given amounts and concentrations from Table 2 for your initial [Fe3+] and [SCN-]
• Use your equilibrium concentrations from the previous step for your [FeSCN2+]eq
4. Calculate Kf
• Use your calculations of [Fe3+], [SCN-] and [FeSCN2+] to find Kf:
• kf = [FeSCN2+][Fe3+][SCN−]