Le Chatelier's Principle and Pressure

[805295074]

Why does a reaction shift towards the reactants when there is an increase in pressure? Is it because they are not dissociated? I read on a website that in a response to an increase in pressure, the reaction will shift to the side with the least amount of moles.

[Christine Ma 3L]

If there is an increase in pressure (as a result of decreasing volume), a reaction only shifts toward the reactants if the reactant side has less moles of gas. If the product side has less moles of gas then the reaction would shift toward the product side.

[JonathanM]

Hey!
So professor Lavelle discussed that the equilibrium doesn't actually change if only the pressure changes such as by adding an inert gas to a gaseous equilibrium, but it will change if volume decreases which also increases pressure. When volume decreases, the concentrations all increase, and if you work through the math of calculating Q and comparing it to K, you find that the equilibrium shifts towards the side of the reaction with fewer total moles of chemicals.
Hope this helps!

[Lauren Sarigumba 1K]

An increase in pressure also means a decrease in volume. It is important to remember that when volume decreases and there are more moles of gas on the left, then the reaction will shift right. And when the volume decreases and there are more moles of gas on the right, then the reaction will shift left. Essentially, whichever way will produce the least amount of moles of gas (and thus the least amount of pressure) then the reaction will favor that same way.

[Jalaia Jackson 2G]

Just as everyone has mentioned, when there's an increase in pressure, the volume will decrease. When the volume decrease to tell if the reaction will shift either left or right, you have to look at the moles of gas on each side of the equation. If there are more moles on the left then the reaction favors the product, if there are more on the right then the reaction favors the reactants.

[Zainab Jamali 1H]

Pressure and volume are inversely related. When pressure increases, volume decreases --> when there is less space to occupy (volume), the reaction will favor the side with fewer moles.

[Melanie Lin 3E]

Hi! A change in pressure will only affect the equilibrium if there's a difference in number of moles of gas on either side of the chemical reaction.