Problem Solving?

Question

At 100 degrees Celsius, Kc=0.078 for the following reaction:

2SO2Cl2 (g) > SO2 (g) + Cl2 (g)

In an equilibrium mixture of the three gases the concentrations of SO2Cl2 is 0.136 M and SO2 is 0.072 M. What is the [Cl2] in the equilibrium mixture?

kindly explain on how to get the answer.
your answer serves as my reviewer to our finals.
thank you very much.

Answer 1

I believe you don't need to place a "2" as the coefficient to SO2Cl2, because it yields exactly SO2 and Cl2 for each SO2Cl2.

Since we are dealing with equilibrium conditions, and I assume that the reaction takes place at 100C, then we have:

0.078=

[SO2][Cl2]/[SO2Cl2]=

[.072][x]/[.136]

solving for x:
.147M of Cl2

In any case, always raise the concentration of the compound to the power of the coeffificient. That is, if you have

2AB--->A2 +B2

Then the Kc would equal:

[A2][B2]/[AB]^2

[AB] is squared because its coefficient is 2. Make sure you have the reaction completely balanced out first, and then apply the formula, and solve for the unknown concentration.