[Frostbytez]

The reaction:

C + CO2 --> 2 CO


occurs at high temperatures. At 700 degrees C a 2.0 L flask contains 0.10 mol of CO, 0.20 mol of CO2, and 0.40 mol of C at equilibrium. Calculate K for the reaction at 700 degrees C.

My book says the answer is K = 0.025 but I'm not sure how they got it. I keep getting 0.125

[vickium]

C + CO2 --> 2 CO

First, I would recommend including the phase subscripts for each molecule in the reaction. When calculating the equilibrium constants, solid and liquid concentrations are constant, so they are omitted from the equilibrium equation.

Next, you will need to find the molarity of each molecule involved:

M = mols solute / L solvent

K = concentration of products / concentration of reactants   or:

K = [CO]^2 / [CO2]   (where [] are Molarities... and I am assuming carbon is solid and the others are gases)

Hope that helps a little

[Borek]

When calculating the equilibrium constants, solid and liquid concentrations are constant

Only pure solids and pure liquids in contact with gas. What you stated may suggest concentrations of solutes are constant, which is not true.