Fe3+(aq)  + SCN−(aq) <-------------------->
FeSCN2+(aq)
1.2x10^-3Â Â Â Â 7.8 x
10^-4Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
0Â Â Â Â Â Â Â Â Â Â Â Â
----------------> initial
1.2x10^-3-x    7.8 x 10^-4 -x
                        Â
x
          Â
---------------->equilibrium
but x = 1.7 x 10^-4 is given
equilibrium concentrations :
[Fe+2] = 1.2x10^-3-x  = 1.03 x 10^-3 M
[SCN-] = 7.8 x 10^-4 -x = 6.1 x 10^-4 M
[FeSCN2+]= 1.7×10^−4 M
equilibrium constant (Kc)Â Â = [FeSCN2+] / [Fe+2]
[SCN-]
                                         Â
= 1.7×10^−4 / (1.03 x 10^-3 ) (6.1 x 10^-4)
                                        Â
= 270.6
equilibrium constant (Kc)Â Â =
270.6
