8. A container is initially charged with 3.50 M of methanol, CH3OH (g). An equilibrium with CH3 and OH is established. The equilibrium concentration of OH was found to be 0.056 M. What is Kc for this reaction?

Question

8.	A container is initially charged with 3.50 M of methanol, CH3OH (g). An equilibrium with CH3 and OH is established. The equilibrium concentration of OH was found to be 0.056 M. What is Kc for this reaction?

matt101 · Answer

First consider the balanced reaction:

CH3OH <--> CH3 + OH

The equation for Kc would therefore be:

Kc=[CH3][OH]/[CH3OH]

Each molecule of CH3OH decomposes into 1 molecule of CH3 and 1 molecule of OH. That means if we have 0.056 M of OH at equilibrium, there must also be 0.056 M of CH3. Moreover, this much CH3OH must have been lost - in other words, the equilibrium concentration of CH3OH must be 3.5-0.056=3.444 M.

Plug these values into your Kc equation and you'll have your answer!