Unchanged K, Changed Pressure

Moderators: Chem_Mod, Chem_Admin

Ayesha Aslam-Mir 3C
Posts: 113
Joined: Wed Sep 30, 2020 9:43 pm

Unchanged K, Changed Pressure

Postby Ayesha Aslam-Mir 3C » Tue Jan 12, 2021 12:00 am

I understand that changing pressure does not change the equilibrium constant, but I just wanted to think about this conceptually: decreasing the volume increases pressure, which increases the reaction rate. So when we look at chemical reactions (here we have conditions iddeal for an increased amount of collisions), altering a condition beyond the available mol for reacting alters overall concentrations?

I guess my confusion comes from if we are altering the mol of reactant by simply altering the concentrations when the reaction (chemical equation) is just based on mol and doesnt account for the conditions of the reaction.

Pranav Kadiyala 1A
Posts: 119
Joined: Wed Sep 30, 2020 9:58 pm

Re: Unchanged K, Changed Pressure

Postby Pranav Kadiyala 1A » Tue Jan 12, 2021 12:13 am

To answer your first question
Ayesha Aslam-Mir 3C wrote:altering a condition beyond the available mol for reacting alters overall concentrations?



Concentration is moles/L. Thus, altering the volume (L) would change the concentration, without altering the number of moles. To answer the second question, we are not changing the number of moles. The concentration changes because the volume changes. This in no way impacts the chemical equation, so it stays constant.

Megan Singer 3D
Posts: 139
Joined: Wed Sep 30, 2020 9:33 pm
Been upvoted: 1 time

Re: Unchanged K, Changed Pressure

Postby Megan Singer 3D » Tue Jan 12, 2021 12:15 am

I'm not sure I fully understand your question, but basically, decreasing the pressure changes the concentrations of the reactants and products because concentration is measured in mol/L. If the moles of the reactants and products stay the same but the volume of the container changes, the concentrations of the reactants and products will change (at least for gases). This means that if Q=K and then you change the pressure of the container by changing its volume, Q will not = K anymore (because the concentrations have changed). The moles of reactants or products will then change as the chemical reaction shifts right or left in order to move back towards equilibrium (K). Whether the forward (forming products) or reverse (forming reactants) reaction is favored depends on the number of total moles of gas there are on each side.


Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 1 guest