volume's effect on K

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Katie Bart 1I
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Joined: Sat Aug 24, 2019 12:16 am

volume's effect on K

Postby Katie Bart 1I » Tue Jan 14, 2020 4:33 pm

So just to confirm, volume affects the products/reactants of a reaction, but it doesn't affect the value of K? And how does volume affect the reactants/products?

Amanda Lin 2I
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Joined: Sat Aug 17, 2019 12:15 am

Re: volume's effect on K

Postby Amanda Lin 2I » Tue Jan 14, 2020 4:41 pm

Yes, K does not change.

A decrease in volume with more moles of gas on the reactant side will cause the reaction to produce more products.
A decrease in volume with more moles of gas on the product side will cause the reaction to produce more reactants.

Andrew Pfeiffer 2E
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Re: volume's effect on K

Postby Andrew Pfeiffer 2E » Tue Jan 14, 2020 4:42 pm

Recall that volume is integrally related to both concentration and pressure. Decreasing the volume with the same amount of reactants and products is going to increase the pressure and concentration, while increasing the volume with the same amount of reactants and products is going to decrease the pressure and concentration. In order to determine which side of the reaction is favored, use the high school trick where you add together the molar coefficients on each side of the equation. Determine which side has a smaller sum. The side (reactants or products) with the smaller coefficient will be favored if pressure/concentration increases, and unfavored if pressure/concentration decreases.

And yes, K stays the same in all these changes. Only temperature will change K.

cassidysong 1K
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Joined: Fri Aug 30, 2019 12:15 am

Re: volume's effect on K

Postby cassidysong 1K » Tue Jan 14, 2020 10:00 pm

When volume changes it changes Q (the reaction quotient) however it does not change K because K is a constant of that molecule at that temperature. The only thing that can change K is temperature.

Angela Prince 1J
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Joined: Sat Aug 24, 2019 12:17 am

Re: volume's effect on K

Postby Angela Prince 1J » Wed Jan 15, 2020 4:14 pm

I know Prof. Lavelle mentioned this in lecture briefly, but why are neither the products nor the reactants favored when the volume decreases and the number of moles are equal on both sides?

LBacker_2E
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Re: volume's effect on K

Postby LBacker_2E » Wed Jan 15, 2020 4:30 pm

Yes, volume, pressure, and changes in concentration have no effect the value of K, only temperature can change the value of the K constant.

Miriam Villarreal 1J
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Joined: Sat Aug 17, 2019 12:16 am

Re: volume's effect on K

Postby Miriam Villarreal 1J » Wed Jan 15, 2020 5:22 pm

Volume has no effect on K because a change in volume – a decrease in volume causes an increase in pressure. To reduce the pressure, the system will try to reduce the number of gas molecules and the reaction will shift to the side with fewer gas molecules.

Bilal Pandit 1J
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Joined: Wed Sep 11, 2019 12:16 am

Re: volume's effect on K

Postby Bilal Pandit 1J » Wed Jan 15, 2020 5:28 pm

K is a constant, so it will essentially always stay the same, with the single exception being temperature due to the change in the kinetic energy of the gas molecules.


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