Chemistry question- equilibrium?

Question

1) At a certain temperature, K=9.1 *10^-4 for the reaction

FeSCN^2+(aq) <---> Fe^3+(aq) + SCN-(aq)

Calculate the concentrations of Fe^3+, SCN-, and FeSCN^2+ in a solution that is initially 2.0 M FeSCN^2+.

2)

Answer 1

1) K = [Fe+++] [SCN-] / [FeSCN--]

FeSCN-- will lose x, and both Fe+++ and SCN- gain x. The equilibrium equation becomes:

9.1*10^-4 = x² / (2.0 - x), which rearranges to:

x² + (9.1*10^-4)x - 1.8*10^-3 = 0.

The only positive root is:

x = 0.042, so

[Fe+++] = [SCN-] = x = 0.042 M

[FeSCN--] = 2.0 - 0.042 = 1.96 M.

2) need more detail here.