In: Chemistry
Consider the following reaction: Fe3+(aq)+SCN−(aq)⇌FeSCN2+(aq) A solution is made containing an initial [Fe3+] of 1.2×10−3 M and an initial [SCN−] of 7.8×10−4 M . At equilibrium, [FeSCN2+]= 1.7×10−4 M .Calculate the value of the equilibrium constant (Kc).
Fe3+(aq) + SCN−(aq) <--------------------> FeSCN2+(aq)
1.2x10^-3 7.8 x 10^-4 0 ----------------> initial
1.2x10^-3-x 7.8 x 10^-4 -x x ---------------->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) = [FeSCN2+] / [Fe+2] [SCN-]
= 1.7×10^−4 / (1.03 x 10^-3 ) (6.1 x 10^-4)
= 270.6
equilibrium constant (Kc) = 270.6