Chemistry Problem
posted by Peter .
At 25 oC, Kc = 0.145 for the following reaction in the solvent CCl4.
2BrCl <> Br2 + Cl2
A solution was prepared with the following initial concentrations: [BrCl] = 0.0482 M, [Br2]= 0.0307 M, and [Cl2]= 0.0277 M.
What will their equilibrium concentrations be?
How do i know when the change in concentration is +x or x?
I tried2BrCl<>Br2 Cl2
.0482 .0307 .0277
2x +x +x
and reverse too but it's wrong. Any ideas?

You must have made a math error.
........2BrCl ==> Br2 + Cl2
I.......0.0482..0.0307..0.0277
First decide which direction the reaction will move? How? Qrxn.
Q = (0.0307)(0.0277)/(0.0482) = 0.0176 and compare this with Kc = 0.145. Q < K which means the fraction is too low in the numerator and too high in the denominator and that means the rxn must go to the right.
C.........2x.......x.......x
E......0.04822x....x.......x
and solve for x. and 0.04822x.If you still have a problem post your work and I'll find the error.