Form 4 chemistry - Reaction Rates Lesson 5 ( Effects of pressure)

The effect of pressure on dynamic equilibrium depends on the number of moles of gas present in the balanced chemical equation. Here are the possible effects:

1. No effect: If the number of moles of gas on both sides of the reaction is equal, changes in pressure will have no effect on the position of the equilibrium. This is because altering the pressure will not favor either the forward or reverse reaction.

2. Effect on side with fewer moles: If the number of moles of gas is different on each side of the reaction, changes in pressure can affect the equilibrium position. Increasing the pressure will decrease the volume, and the equilibrium will shift towards the side with fewer moles of gas. Conversely, decreasing the pressure will increase the volume, causing the equilibrium to shift towards the side with more moles of gas.

It is important to note that changes in pressure do not affect the value of the equilibrium constant (K), which remains the same. Also, it is worth mentioning that pressure changes only affect equilibria involving gases, not reactions involving only solids or liquids.