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Topic: Pressure's effect on equilibrium  (Read 771 times)

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Offline thepackage

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Pressure's effect on equilibrium
« on: January 03, 2024, 02:45:54 AM »
At equilibrium, if pressure is increased, then the equilibrium will shift to favour the reaction producing the least amount of molecules. e.g 3A  ::equil::  2B. In this reaction, if pressure is increased, then the reaction will shift to the right to produce more of B.

Would this mechanism result in pressure decreasing until it reaches its initial levels?

Also how can K (equilibrium constant), remain a constant? because pressure changes will alter concentrations of the substances, hence K will change based on pressure.

Offline Borek

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Re: Pressure's effect on equilibrium
« Reply #1 on: January 03, 2024, 03:22:07 AM »
Would this mechanism result in pressure decreasing until it reaches its initial levels?

Until the system reaches new equilibrium, at pressures higher than initial.

Quote
Also how can K (equilibrium constant), remain a constant? because pressure changes will alter concentrations of the substances, hence K will change based on pressure.

Are you sure you are not mistaking Q (reaction quotient) with K (equilibrium constant)? Because yes, when you increase the pressure Q will initially change, but then the system will react till Q=K (also note you can describe the system with both pressures and concentrations, getting different equilibrium constants Kc and Kp, they are identical only when there is no volume change between reactants and products).
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Offline milosevicChelsea

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Re: Pressure's effect on equilibrium
« Reply #2 on: January 05, 2024, 12:33:45 AM »
Yes, you are right ....the raction will shift from left to right...
Also, you are right...the constant K won't change...(assuming we haven't changed the temperature)

Now, we need to think...how to change the preassure...
We have two options...one is to reduce the volume of the raction vessel...or to put more material into the reaction vessel (A, B, or both). This means that we have disturbed the equilibrioum and the reaction will continue until the quantity of reactants and products is obtained which will result in the constant K.

Offline Vidya

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Re: Pressure's effect on equilibrium
« Reply #3 on: January 06, 2024, 07:29:28 AM »
At equilibrium, if pressure is increased, then the equilibrium will shift to favour the reaction producing the least amount of molecules. e.g 3A  ::equil::  2B. In this reaction, if pressure is increased, then the reaction will shift to the right to produce more of B.

Would this mechanism result in pressure decreasing until it reaches its initial levels?
Also how can K (equilibrium constant), remain a constant? because pressure changes will alter concentrations of the substances, hence K will change based on pressure.
K will not change as you are not changing the temperature.
However as the pressure on the system increases by decreasing the volume , system will come in non equilibrium state (Q) and then it will shift in the direction of low pressure ( product in the example) and will get new equilibrium pressure which gives the same value of K .
Q= pB^2/pA^3
Reaction will shift in the direction of B till the above ratio has the same value as K .
At equilibrium Q=K

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