Pressure is the inverse of Volume so If you understand how the dynamic equilibrium is altered by changes in pressure then you understand what occurs for changes in volume.
First thing you want to do here is remind yourself. Pressure only changes the amounts of the Gases in the reaction. Because of this only count the number of moles from the gases when following the next steps.
Step One: Count all of the moles of each of the gases in the reaction and add them up. Only add up what is on the left by itself and what is on the right by itself. When you get that answer, Identify which side of the equation has the higher number of moles of gases.
Step Two: Identify by looking at the question whether or not the pressure is increasing or decreasing.
Step Three: If the Pressure is increasing, the Dynamic Equillibrium will shift in the direction of the side of the reaction that has less moles.
Step Four: If the Pressure is decreasing, the Dynamic Equilibrium will shift in the direction of the side of the reaction that has more moles.
