Question

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 tried-2BrCl<-->Br2 Cl2

.0482 .0307 .0277
-2x +x +x

and reverse too but it's wrong. Any ideas?

Answer 1

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......0.0482-2x....x.......x

and solve for x. and 0.0482-2x.If you still have a problem post your work and I'll find the error.

Answer 2

You are wrong!!!!!!