Question

For the following reaction, Kc = 255 at 1000 K.
CO(g)+Cl2(g)?COCl2(g)
A reaction mixture initially contains a COconcentration of 0.1450 M and a Cl2concentration of 0.174 M at 1000 K.

What is the equilibrium concentration of CO at 1000 K?

Answer 1

According to the reaction equation:
CO(g) + Cl2(g) ? COCl2(g)
the equilibrium concentrations in M are related as:
Kc = [COCl2] / ( [CO]*[Cl2])
with Kc = 255
........... [CO]......... [Cl2].......... [COCl2]
I.......... 0.145....... 0.174............. 0
C........... -x............ -x...............+x
E....... 0.145 -x.... 0.174-x.......... x

When you substitute the expressions for the equilibrium concentrations from the last row of the table to the equilibrium equation you get:
255 = x / ( (0.145 - x)?(0.174 - x))
<=>
255 (0.145 - x)(0.174 - x) = x
255(0.02523 - 0.319x + x^2) = x
255x^2 - 82.345x + 6.434 = 0
x = [82.345