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

(aq)colorless colorless

]SCN[ ][Fe

][Fe(SCN)K

equilequil3

equil2

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

(aq)colorless colorless reddish-orange

  A (blank) B C D E

volume of 0.200 M Fe3+ 10.0 mL 10.0 mL 10.0 mL 10.0 mL 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 for calibration curve Pg. 32

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

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

Experimental absorbance [Fe(SCN)2+], M

solution 1

solution 2

solution 3

solution 4

solution 5

Pg. 36

  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+ 2.50 2.50 2.50 2.50 2.50 2.50

mL 0.200 M HNO3 2.50 2.00 1.50 1.00 0.50 0.00

Experimental Solutions Pg. 34

Experimental test solutions

Experimental 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

Calibration Curve

0.00E+00

4.00E-05

8.00E-05

1.200E-04

1.600E-04

2.96E-05

5.92E-05

1.40E-041.16E-04

8.81E-05

y = 4697.5x + 0.0008

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.00E+00 5.00E-05 1.00E-04 1.50E-04 2.00E-04

[Fe(SCN)2+], M

abs

orb

an

ce

Standards

Experimentals

Experimental absorbance [Fe(SCN)2+], M

solution 1 0.139 2.96 x 10-5

solution 2 0.278 from graph

solution 3 0.414 from graph

solution 4 0.546 from graph

solution 5 0.658 from graph

Experimental test solutions

Pg. 36

Calibration Curve

0.00E+00

4.00E-05

8.00E-05

1.200E-04

1.600E-04

2.96E-05

5.92E-05

1.40E-041.16E-04

8.81E-05

y = 4697.5x + 0.0008

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.00E+00 5.00E-05 1.00E-04 1.50E-04 2.00E-04

[Fe(SCN)2+], M

abs

orb

an

ce

Standards

Experimentals

Experimental 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 from graph

solution 5 0.658 from graph

Experimental test solutions

Pg. 36

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

Experimental test solutions

Initial Concentrations for Trial 1

mL00.5

)mL50.2()FeM00200.0(]Fe[ initial

33

33 Fe M 10 x 1.00

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

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 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3

[SCN-]initial

[Fe3+]equil

[SCN-]equil

K

Average K

Experimental test solutions

Initial Concentrations for Trial 1

mL00.5

)mL50.0()SCNM00200.0(]SCN[ initial

SCN M 10 x 2.00 4

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 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3

[SCN-]initial 2.00 x 10-4

[Fe3+]equil

[SCN-]equil

K

Average K

Experimental test solutions

[ ], M Fe3+ (aq) + SCN- (aq) Fe(SCN)2+ (aq)

initial 1.00 x 10-3 2.00 x 10-4   0

change x 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

[SCN-]equil = [SCN-] 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 = 2.00 x 10-4 M – 2.96 x 10-5 M = 1.70 x 10-4 M

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 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3

[SCN-]initial 2.00 x 10-4

[Fe3+]equil 9.70 x 10-4

[SCN-]equil

K

Average K

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 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3 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

Experimental test solutions

]SCN[ ][Fe

][Fe(SCN)K

equilequil3

equil2

Determine the numerical value of the equilibrium constant, K

M) 10 x 70.1( M) 10 x 70.9(

M) 10 x 96.2( K

44

5

= 179

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 1.00 x 10-3 1.00 x 10-3 1.00 x 10-3 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

Experimental test solutions