Equilibrium constant for general chemistry

Equilibrium constant for general chemistry lab

1. Equilibrium constant Is it really constant?

2. The reaction Fe 3+  + SCN -   ®  [Fe(SCN)] 2+ K c = [FeSCN 2+ ] [Fe 3+ ][SCN - ] blood red

3. Colored complexes Fe : [ Ar ] 18 4s 2 3d 6 Fe 3+ : [ Ar ] 18 3d 5

4. Absorbance and conc. A = log (1/T) A = ε cl A = (constant)c

5. Fe 3+  + SCN -   ®  [Fe(SCN)] 2+ [Fe 3+ ] : 0.15 M [SCN - ] : 0.0015 M Le Chatlier’s principle [FeSCN 2 + ] : ?

6. Goals 1. Measure K c with high precision and accuracy 2. Effect of solution ionic strength on K c

7. Effect of ionic strength When ionic strength increases; Fe 3+ and SCN - are not going to be as strongly attracted to each other How does that effect K c ?

8. Data sharing Each group is assigned one KNO 3 concentration Determine K c for that concentration Post results on eLC discussion board: KNO 3 conc. Mean K c value Deviation from mean

9. Deadline March 16 Wednesday 11:59 PM Loss of 15 points