CHEMISTRY COMMUNITY

Can someone explain to me what Dr. Lavelle was explaining in class about the true reason why increasing pressure goes to the side with fewer moles of gas?

When you increase pressure, you are decreasing the volume. This relationship is seen in the PV=nRT equation. A decrease in volume means an increase in concentration. To balance out the increase in concentration, the equilibrium will go toward the side with fewer moles.

the increasing pressure causes the side with more moles to produce more of the side with less moles. im not sure what lavelle was talking about but that's the concept of his explanation.

He explained that if pressure is increased by decreasing volume (if a piston pushed down on the reaction, for example) then the concentration of each of the gases in the reaction would increase. We calculate concentration by using where n is moles of gas and V is the volume of the container. If the pressure doubled by decreasing the volume of the container by half, then the new concentrations would be doubled. If one side of the reaction has more moles of gas, then once we plug in the new concentration we would see a change in Q which would push the reaction toward the side with fewer moles of gas.

This does not happen when you increase the pressure by adding an inert gas. If you add an inert gas, the each gas' moles and volume do not change. This means the concentrations do not change, so nothing happens to the reaction.

Pressure only affect the equilibrium concentration if there is a change in volume since a change in volume will affect the concentration of the molecules involved in the chemical reaction because of the formula Concentration=n/V. Increasing pressure by adding inert gas will not affect the volume and therefore will not affect the concentration of R and P.