The Determination of Keq for FeSCN 2+

The Lab

The Determination of Keq for FeSCN2+

1. Name, Lab Partners, Date: 

2. Pre-Lab Questions:

Le Chatelier's principle states that the system will shift to reestablish equilibrium when more Fe ions are added to the system. The addition of Fe ions causes the system to shift right to produce more FeSCN by reacting with the SCN- ions. Therefore, a constant addition of Fe ions will lead to an equilibrium concentration equal to the initial concentration of SCN- ions, as they all get used up.

Calculation

[FeSCN 2+]eq (M2)

Reference Solution 1

(0.0002(2))/10 = M2

4.0 x 10^-5

Reference Solution 2

(0.0002(3))/10 = M2

6.0 x 10^-5

Reference Solution 3

(0.0002(4))/10 = M2

8.0 x 10^-5

Reference Solution 4

(0.0002(5))/10 = M2

1.0 x 10^-4

Reference Solution 5

(0.0002(6))/10 = M2

1.2 x 10^-4

[Fe 3+]

[SCN-]

Reference Solution 6

1.0 x 10^-3

2.0 x 10^-4

Reference Solution 7

1.0 x 10^-3

4.0 x 10^-4

Reference Solution 8

1.0 x 10^-3

6.0 x 10^-4

Reference Solution 9

1.0 x 10^-3

8.0 x 10^-4

Reference Solution 10

1.0 x 10^-3

1.0 x 10^-3

Calculations:

[Fe 3+]

[SCN-]

Test Solution 6

(0.002(5))/10=M2

(0.002(1))/10=M2

Test Solution 7

(0.002(5))/10=M2

(0.002(2))/10=M2

Test Solution 8

(0.002(5))/10=M2

(0.002(3))/10=M2

Test Solution 9

(0.002(5))/10=M2

(0.002(4))/10=M2

Test Solution 10

(0.002(5))/10=M2

(0.002(5))/10=M2

3. Objective: Determine the equilibrium constant, K, for FeSCN 2+ from the experimentally determined equilibrium concentrations of FeSCN 2+, Fe 3+, and SCN-.