1. EXPERIMENT 3 – DETERMINATION OF THE Keq
[Fe(NO3)3] M
[KSCN] M
[Fe3+]init M
[SCN-]init M
[FeSCN2+]init
0 M 5
5.00
2.00
3.00
EX3-1 (of 4)

2. EXPERIMENT 3 – DETERMINATION OF THE Keq
Absorbance:
A = (3425 M-1)c
= (3425 M-1)c
= (3425 M-1)c
= c
___________
3425 M-1
M = c
= [FeSCN2+]eq
EX3-2 (of 4)

3. EXPERIMENT 3 – DETERMINATION OF THE Keq
Fe3+ (aq) SCN- (aq) ⇆ FeSCN2+ (aq)
Initial M’s
Change in M’s
Equilibrium M’s
- x
- x
+ x x x x
Kc = [FeSCN2+]
_______________
[Fe3+][SCN-]
Kc = x
_________________________________
( – x)( – x)
[FeSCN2+]eq = x
= M
EX3-3 (of 4)

4. EXPERIMENT 3 – DETERMINATION OF THE Keq
Fe3+ (aq) SCN- (aq) ⇆ FeSCN2+ (aq)
Initial M’s
Change in M’s
Equilibrium M’s
- x
- x
+ x x x x
Kc = [FeSCN2+]
_______________
[Fe3+][SCN-]
[Fe3+]eq =
[SCN-]eq =
[FeSCN-]eq =
– x
– x x
= M
= M
= M
x = M
Kc = ( M)
_________________________________
( M)( M)
= M-1
EX3-4 (of 4)