Consider N
2 + 3H
2 2NH
3First, I want to ask you.
For this equation, when pressure increases, do you know the reason for why more N
2 and H
2 will be converted to NH
3 but not the other way round?
It's because there are less molecules on the right hand side of the equation compared to the left. The system will convert more N
2 + H
2 to become NH
3 to reduce the number of molecules, hence reduce the pressure and consequentially reduce the change. Do you know this?
Assume that you know this, therefore is this your question: Why does rate of reaction of N
2 + H
2 increase when the pressure applied on the system increases?
My explanation is:
As you provide more physical pressure on the system, you are actually decreasing the volume of the whole system. As the forward reaction will reduce the number of molecules, the volume of the whole system will decrease also, as less molecules occupy less space. Vice-versa for backward reaction. Therefore, when you provide physical pressure, which decreases the volume, you are actually helping the forward reaction to happen, while slowing down the backward reaction. Therefore, the rate of forward reaction increases while the rate of backward reaction decreases at the same time.