Fe3+ (aq) + SCN- (aq) Fe(SCN)2+ (aq) colorless colorless

Fe3+ (aq) Fe(SCN)2+ (aq) + SCN- (aq) colorless colorless reddish-orange

equilibrium [Fe(SCN)2+], M Standard Solutions for calibration curve Pg. 32   A (blank) B C D E volume of 0.200 M Fe3+ 10.0 mL volume of 0.00200 M SCN- 0.00 mL 0.50 mL 1.00 mL 1.50 mL 2.00 mL 0.200 M HNO3 dilute to 25.00 mL mark equilibrium [Fe(SCN)2+], M 0.00 4.00 x 10-5 8.00 x 10-5 12.0 x 10-5 16.0 x 10-5

Standard solutions Standards [Fe(SCN)2+], M absorbance standard A 0.00 standard B 4.00 x 10-5 standard C 8.00 x 10-5 standard D 12.0 x 10-5 standard E 16.0 x 10-5 Pg. 36

Standard solutions Standards [Fe(SCN)2+], M absorbance standard A 0.00 0.000 standard B 4.00 x 10-5 0.196 standard C 8.00 x 10-5 0.371 standard D 12.0 x 10-5 0.557 standard E 16.0 x 10-5 0.759 Pg. 36

Experimental test solutions absorbance [Fe(SCN)2+], M solution 1 solution 2 solution 3 solution 4 solution 5 Pg. 36

Experimental Solutions Pg. 34   Blank 1 2 3 4 5 mL 0.00200 M SCN- 0.00 0.50 1.00 1.50 2.00 2.50 mL 0.00200 M Fe3+ mL 0.200 M HNO3

Experimental test solutions absorbance [Fe(SCN)2+], M solution 1 0.139 solution 2 0.278 solution 3 0.414 solution 4 0.546 solution 5 0.658 Pg. 36

Standard solutions Standards [Fe(SCN)2+], M absorbance standard A 0.00 0.000 standard B 4.00 x 10-5 0.196 standard C 8.00 x 10-5 0.371 standard D 12.0 x 10-5 0.557 standard E 16.0 x 10-5 0.759 Pg. 36

Experimental test solutions absorbance [Fe(SCN)2+], M solution 1 0.139 2.96 x 10-5 solution 2 0.278 from graph solution 3 0.414 solution 4 0.546 solution 5 0.658 Pg. 36

Experimental test solutions absorbance [Fe(SCN)2+], M solution 1 0.139 2.96 x 10-5 solution 2 0.278 5.92 x 10-5 solution 3 0.414 from graph solution 4 0.546 solution 5 0.658 Pg. 36

[Fe(SCN)2+]equil (graph) Experimental test solutions units are M 1 2 3 4 5 [Fe(SCN)2+]equil (graph) 2.96 x 10-5 [Fe3+]initial [SCN-]initial [Fe3+]equil [SCN-]equil K Average K

Initial Concentrations for Trial 1

[Fe(SCN)2+]equil (graph) Experimental test solutions units are M 1 2 3 4 5 [Fe(SCN)2+]equil (graph) 2.96 x 10-5 [Fe3+]initial 1.00 x 10-3 [SCN-]initial [Fe3+]equil [SCN-]equil K Average K

[Fe(SCN)2+]equil (graph) Experimental test solutions units are M 1 2 3 4 5 [Fe(SCN)2+]equil (graph) 2.96 x 10-5 [Fe3+]initial 1.00 x 10-3 [SCN-]initial [Fe3+]equil [SCN-]equil K Average K

Initial Concentrations for Trial 1

[Fe(SCN)2+]equil (graph) Experimental test solutions units are M 1 2 3 4 5 [Fe(SCN)2+]equil (graph) 2.96 x 10-5 [Fe3+]initial 1.00 x 10-3 [SCN-]initial 2.00 x 10-4 [Fe3+]equil [SCN-]equil K Average K

x = [Fe(SCN)2+]equil (obtained from graph) Fe3+ (aq) + SCN- (aq) Fe(SCN)2+ (aq) initial 1.00 x 10-3 2.00 x 10-4   change x +x equilibrium 1.00 x 10-3 x 2.00 x 10-4 x x x = [Fe(SCN)2+]equil (obtained from graph)

Equilibrium Concentrations for Trial 1 [Fe3+]equil = [Fe3+]­initial – [Fe(SCN)2+]equil [Fe3+]equil = 1.00 x 10-3 M – 2.96 x 10-5 M = 9.70 x 10-4 M [SCN-]equil = [SCN-]­initial – [Fe(SCN)2+]equil [SCN-]equil = 2.00 x 10-4 M – 2.96 x 10-5 M = 1.70 x 10-4 M

[Fe(SCN)2+]equil (graph) Experimental test solutions units are M 1 2 3 4 5 [Fe(SCN)2+]equil (graph) 2.96 x 10-5 [Fe3+]initial 1.00 x 10-3 [SCN-]initial 2.00 x 10-4 [Fe3+]equil 9.70 x 10-4 [SCN-]equil K Average K

[Fe(SCN)2+]equil (graph) Experimental test solutions units are M 1 2 3 4 5 [Fe(SCN)2+]equil (graph) 2.96 x 10-5 [Fe3+]initial 1.00 x 10-3 [SCN-]initial 2.00 x 10-4 [Fe3+]equil 9.70 x 10-4 [SCN-]equil 1.70 x 10-4 K Average K

Determine the numerical value of the equilibrium constant, K = 179

[Fe(SCN)2+]equil (graph) Experimental test solutions units are M 1 2 3 4 5 [Fe(SCN)2+]equil (graph) 2.96 x 10-5 [Fe3+]initial 1.00 x 10-3 [SCN-]initial 2.00 x 10-4 [Fe3+]equil 9.70 x 10-4 [SCN-]equil 1.70 x 10-4 K 179 Average K