Pressure Increases in Closed Systems

[Karrin Evans 1C]

In lecture, Prof. Lavelle gave this example: 2 mol gas --> 4 mol gas, creating an increase in pressure. I understand that we're increasing the moles of gas within the system, but I don't understand how that increases the pressure. We're not creating more atoms, so where does the extra pressure come from? Is it because the product is less dense than the reactant?

[kamrin schultz 2J]

According to the ideal gas law (PV=nRT), at constant temperature and volume, pressure is directly proportional to the number of moles.

[mieke van daelen 2I]

I like to think about the ideal gas law and the relationships between the different variables. in PV=nRT, concentration (n) and pressure (P) are proportional, so an increase in concentration would increase pressure.

[Ivy Zhang 2A]

To add on and provide a conceptual example, increasing the number of gas moles in a closed system will cause a greater number of gas molecule impacts on the container walls, which results in an increase in pressure within the closed system.

[Sydney]

I like to visualize it by thinking about the collisions between the molecules in the container. When the number of molecules in a container of the same size increases, the molecules collide more frequently and these collisions exert more pressure from the inside of their container.

[Emily_Hanna_2E]

Hi Karrin! I understand where you're coming from, so I think that it is best to think about it in regards to the ideal gas law. As the ideal gas law equation is PV=nRT, we can see that when there is an increase in moles (the right side of the equation is going to increase), so the left side of the equation must increase as well which will cause there to be an increase in pressure if volume is constant. As a visual, when you increase moles, there are more molecules hitting the walls of the container so pressure would increase. Hope this was helpful!

[Karrin Evans 1C]

Hi Karrin! I understand where you're coming from, so I think that it is best to think about it in regards to the ideal gas law. As the ideal gas law equation is PV=nRT, we can see that when there is an increase in moles (the right side of the equation is going to increase), so the left side of the equation must increase as well which will cause there to be an increase in pressure if volume is constant. As a visual, when you increase moles, there are more molecules hitting the walls of the container so pressure would increase. Hope this was helpful!

Wait that's so helpful, thank you so much!