Quiz: le Châtelier – Pressure

Consider the following equilibrium reaction (NO2 is brown, and N2O4 is colorless):

2 NO2 (g)    N2O4 (g)

1. If you increase the pressure (by decreasing the volume of the container in which the reaction is carried out), then

a) the brown color will intensify
b) the brown color will get lighter
c) there will be no change in the color

The decomposition reaction of PCl5 is often used in beginning chemistry to show the effect of pressure on an equilibrium:

PCl5 (g)     PCl3 (g)  +  Cl2 (g)

2. Which of the following should happen if the volume increases?

Applied Stress Le Châtelier's Principle Prediction of Response to Stress
PCl5 (g) PCl3 (g) +  Cl2 (g)
Increase P Increase Decrease Decrease
Increase P Decrease Increase Increase
Decrease P Decrease Increase Increase
Decrease P Increase Decrease Decrease

3. What would be the effect of a change in pressure on this reaction?

2 HI (g)    H2 (g)  +  I2 (g)
Applied Stress Le Châtelier's Principle Prediction of Response to Stress
2 HI (g) H2 (g) + I2 (g)
Increase P Increase Decrease Decrease
Increase P Decrease Increase Increase
Decrease P Decrease Increase Increase
Decrease P No Change No Change No Change

In some reactions, such as the following, there will be both gases, and other states of matter.

CaCO3 (s)    CO2 (g)  + CaO (s)

4. Which of the following is the effect of an change in pressure on this reaction?

Applied Stress Le Châtelier's Principle Prediction of Response to Stress
CaCO3 (s) CO2 (g) +CaO (s)
Increase P Increase Decrease Decrease
Increase P Decrease Increase Increase
Decrease P Increase Decrease Decrease
Decrease P No Change No Change No Change