The document discusses how changing the pressure affects the equilibrium of reversible gas reactions. It states that if the pressure is increased, the equilibrium will shift in the direction that decreases the number of gas molecules. If the pressure is decreased, the equilibrium will shift in the direction that increases the number of gas molecules. It also provides the example of nitrogen dioxide and dinitrogen tetroxide, explaining that if the pressure of this system is increased, more dinitrogen tetroxide will be produced.

1. Pressure and equilibrium
Changing the pressure has an effect on the equilibrium of
reversible reactions involving gases.

2. Pressure and equilibrium
Changing the pressure has an effect on the equilibrium of
reversible reactions involving gases.
If the pressure is increased:
 equilibrium shifts to decrease the pressure
 equilibrium shifts in the direction of fewest
molecules

3. Pressure and equilibrium
Changing the pressure has an effect on the equilibrium of
reversible reactions involving gases.
If the pressure is increased:
 equilibrium shifts to decrease the pressure
 equilibrium shifts in the direction of fewest
molecules
If the pressure is decreased:
 equilibrium shifts to increase the pressure
 equilibrium shifts in the direction of most
molecules

4. Opposing changes in pressure

5. Opposing changes in pressure
Nitrogen dioxide is in constant equilibrium with dinitrogen
tetroxide. Two molecules of nitrogen dioxide react to form
one molecule of dinitrogen tetroxide.

6. Opposing changes in pressure
Nitrogen dioxide is in constant equilibrium with dinitrogen
tetroxide. Two molecules of nitrogen dioxide react to form
one molecule of dinitrogen tetroxide.
nitrogen dioxide dinitrogen tetroxide
2NO2 (g) N2O4 (g)

7. Opposing changes in pressure
Nitrogen dioxide is in constant equilibrium with dinitrogen
tetroxide. Two molecules of nitrogen dioxide react to form
one molecule of dinitrogen tetroxide.
nitrogen dioxide dinitrogen tetroxide
2NO2 (g) N2O4 (g)
What will happen if the pressure is increased?

8. Opposing changes in pressure
Nitrogen dioxide is in constant equilibrium with dinitrogen
tetroxide. Two molecules of nitrogen dioxide react to form
one molecule of dinitrogen tetroxide.
nitrogen dioxide dinitrogen tetroxide
2NO2 (g) N2O4 (g)
What will happen if the pressure is increased?
 The equilibrium will shift to reduce the number of
molecules, i.e. to the right (only 1 molecule).
 More N2O4 will be produced.

9. Opposing changes in pressure
Nitrogen dioxide is in constant equilibrium with dinitrogen
tetroxide. Two molecules of nitrogen dioxide react to form
one molecule of dinitrogen tetroxide.
nitrogen dioxide dinitrogen tetroxide
2NO2 (g) N2O4 (g)
What will happen if the pressure is increased?
 The equilibrium will shift to reduce the number of
molecules, i.e. to the right (only 1 molecule).
 More N2O4 will be produced.
If the pressure is decreased, more NO2 will be produced.