In: Chemistry
The reaction Fe3+(aq)+ SCN-(aq)FeSCN2+(aq)is initiated by mixing 1.50 mL of 0.0060 M iron nitrate (Fe3+) with 0.75mL of 0.0020 M KSCN (SCN-) and enough water to give a total volume of 3.0 mL in a cuvette. The reaction goes to equilibrium with a final concentration of 1.55 x 10-4M FeSCN2+. Calculate Kc at 25°C for the reaction. Answer on the back side of this page. (Hint:calculate the initial concentrations of Fe3+ and SCN in the cuvette and use an ICE table
concentration of Fe3+ = 1.50 x 0.0060 / 3.0
= 0.0030 M
concentration of SCN- = 0.75 x 0.0020 / 3.0
= 0.00050 M
Fe3+ (aq) + SCN- (aq) ------------> FeSCN2+ (aq)
0.0030 0.00050 M 0
0.0030-x 0.00050 - x x
[FeSCN2+] = x = 1.55 x 10^-4 M
[Fe3+] = 0.002845 M
[SCN-] = 3.45 x 10^-4 M
Kc = [FeSCN2+] / [Fe3+][SCN-]
= (1.55 x 10^-4) / (0.002845 )(3.45 x 10^-4 )
Kc = 158