I am currently attempting the following problem:
At a certain temperature K = 1.1 x 103 L/mol for the following reaction:
Fe3+(aq) + SCN-(aq) <-------> FeSCN2+(aq)
Calculate the concentrations of Fe3+, SCN-, and FeSCN2+ at equilibrium if 0.02 moles of Fe(NO3)3 is added to 1L of 0.01M KSCN. (Neglect any volume change)
My attempt:
With the provided amounts of compounds, once placed in an aqueous solution, there will be a concentration of 0.02M Fe3+, and 0.1M SCN-.
Constructing an ICe table:
Fe3+(aq) + SCN-(aq) <-------> FeSCN2+(aq)
Initial: 0.02M 0.1M 0M
Change: -x -x +x
Equilibrium: 0.02 - x 0.1 - x x
The quadratic equation would then be:
x/(0.02-x)(0.1-x) = 1.1*103
Simplifying to:
1100x2 - 113.2x + 2.2 = 0
Solving for x, the two values would be
x1 = 0.0769
x2 = 0.026
However, both values can't be correct since I only have 0.02M of Fe3+. Even if I round 0.026 to 0.02, I would get 0M, which isn't what the answer states. (Answer being 2*10-4)
So where did I go wrong?
Thank you in advance!