What is the effect of a volume decrease on the reaction?

Question

What is the effect of a volume decrease on the reaction C(s) + H2O(g) → CO(g) + H2(g) ?

1. K decreases.

2. More CO(g) and H2(g) are produced.

3. More H2O(g) are produced.

4. no change

5. K increases

Answer 1

Hi Nick!

This is a question that's got to do with shifts in equilibrium, or Le Chatelier's principle.

Let's look at each one...for answers 1 and 5, this is a common misconception. Always remember, the K of a reaction is dependent on the temperature of the reaction alone; that's why we have the Arrhenius equation. So those two are both out.

For 2, 3, and 4, we're basically saying a shift right, shift left, or no shift in equilibrium at all. If you look closely at the equation, you'll see that there are two moles of gas on the right, and only one mole of gas on the left. When we compress a closed system, we effectively reduce the amount of space for gas molecules to occupy, and we tend to favor having less moles overall. Based on that, reducing the volume would cause the reaction to shift to the left (answer 3), creating more H2O (g).

CORRECTION: Shift to the left (answer 3)