Pressure Rule

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305421980
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Pressure Rule

Postby 305421980 » Tue Mar 10, 2020 7:28 pm

When looking at a reaction at equilibrium and trying to decide which way the reaction will proceed with a decrease in pressure, I know we are supposed to chose the side with less moles. But if there is a solid on one side of the reaction should we count the moles it contributes or do all of the elements need to be in the gaseous phase when looking at the pressure aspect of Le Chatelier's Principle?

Vinita Saxena 2I
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Re: Pressure Rule

Postby Vinita Saxena 2I » Tue Mar 10, 2020 7:51 pm

Only count the moles of gas, those are the ones most affected by a change in pressure

Clara Cho 2K
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Re: Pressure Rule

Postby Clara Cho 2K » Tue Mar 10, 2020 8:03 pm

I'm pretty sure you do not count the solids and liquids.

Sartaj Bal 1J
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Re: Pressure Rule

Postby Sartaj Bal 1J » Wed Mar 11, 2020 9:48 am

This only applies to gases because liquids and solids are incompressible.

kevinolvera1j
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Re: Pressure Rule

Postby kevinolvera1j » Fri Mar 13, 2020 3:19 pm

Only pay attention to gases because they can be compressed.

Danielle DIS2L
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Re: Pressure Rule

Postby Danielle DIS2L » Sun Jan 10, 2021 9:50 pm

we only include the moles of gas and not solids and liquids.

My-Lan Le 1L
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Re: Pressure Rule

Postby My-Lan Le 1L » Tue Jan 12, 2021 12:24 pm

Solids and liquids are not counted because they can not be compressed. So you would just need to focus on the moles of a compound/molecule that are in a gas phase.

Yashvi Reddy 1H
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Re: Pressure Rule

Postby Yashvi Reddy 1H » Tue Jan 12, 2021 4:44 pm

Hi! Good question, and I agree with the answers above. We only consider the gases, and we do not include liquids or solids. I hope this was helpful!

Karina Grover 1A
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Re: Pressure Rule

Postby Karina Grover 1A » Tue Jan 12, 2021 5:08 pm

In compliance with previous responses, you only have to take into account the moles of gas on either side of the reaction. If there is only a solid on one side, then that side would have 0 moles of gas and thus, fewer moles of gas than the other side.

Juwon Lim 2A
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Re: Pressure Rule

Postby Juwon Lim 2A » Tue Jan 12, 2021 5:44 pm

It shouldn't matter whether the reaction is heterogeneous or homogenous. Pressure only affects gases, so we just add the moles of gas on each side of the reaction and compare.

Becca Nelson 3F
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Re: Pressure Rule

Postby Becca Nelson 3F » Wed Jan 13, 2021 12:35 pm

We are always trying to see how Q compares to K when trying to see what will happen with non-equilibrium conditions, and solids and liquids are not included in the equation for K, so they should be disregarded. Also, pressure really only relates to gases anyways.

VincentLe_3A
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Re: Pressure Rule

Postby VincentLe_3A » Wed Jan 13, 2021 3:28 pm

Only gases are affected by an increase or decrease in pressure through a change in volume specifically. It is important to note that a change in pressure due to an addition of an inert gas will have no effect on the overall reaction.

Lorraine Jiang 2C
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Re: Pressure Rule

Postby Lorraine Jiang 2C » Thu Jan 14, 2021 12:12 am

Hi! So only gases are affected when there is a change in pressure so I think we don’t look at solids and liquids and we only look at gases in the reaction.

Hope it helps!

Joshua Swift
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Re: Pressure Rule

Postby Joshua Swift » Fri Jan 15, 2021 5:12 pm

Liquids and Solids from the reaction are not included, you only need to account for the moles of gas

Jiapeng Han 1C
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Re: Pressure Rule

Postby Jiapeng Han 1C » Fri Jan 15, 2021 11:32 pm

We should only count the moles of gas molecules because they are the ones that will be affected by changes in pressure. By the way, solid and liquid play no role in the calculation of the equilibrium constant.

Juliet Carr 1F
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Re: Pressure Rule

Postby Juliet Carr 1F » Sat Jan 16, 2021 11:39 pm

When changing the pressure of a system make sure to only focus on the moles of gas to see the effects on the reaction. Do not account for the moles of solid, liquid, or aqueous compounds when examining the effects of altering the pressure/ volume.

Shana Patel 1C
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Re: Pressure Rule

Postby Shana Patel 1C » Sun Jan 17, 2021 12:05 am

This only applies to gases because they can be compressed. However, liquids and solids cannot be compressed therefore could not work.

Carly_Lipschitz_3H
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Re: Pressure Rule

Postby Carly_Lipschitz_3H » Sun Jan 17, 2021 9:21 am

If there is a solid on one side of the reaction, don't count the moles it contributes. All the elements must be in the gaseous phase because gas is related to pressure. Only take into account gas molecules, not even aqueous, solids, or liquids when dealing with pressure.

AnjikaFriedman-Jha2D
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Re: Pressure Rule

Postby AnjikaFriedman-Jha2D » Sun Jan 17, 2021 9:42 am

you only look at the moles of gases because gases are the ones that are contributing to the pressure in the reaction vessel.

Kyla Roche 2K
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Re: Pressure Rule

Postby Kyla Roche 2K » Sun Jan 17, 2021 10:24 am

Only count the moles of the gas because those are included in K equation and gases have the partial pressures. Don't include solids and liquids.

Chinmayi Mutyala 3H
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Re: Pressure Rule

Postby Chinmayi Mutyala 3H » Sun Jan 17, 2021 2:42 pm

You only look at molecules in the gas phase since those are the one's whose concentration is affected by a change in pressure. However, this change in pressure must cause a change in the volume of the container. If the pressure is changed by adding another gas, it won't affect the concentrations of the gases so K would not change and the reaction would still be at equilibrium.

DavidTabib 3H
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Re: Pressure Rule

Postby DavidTabib 3H » Sun Jan 17, 2021 5:58 pm

The moles of the solids and liquids do not count.

Coleman Morrow
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Re: Pressure Rule

Postby Coleman Morrow » Sun Jan 17, 2021 6:03 pm

If the solid is still an unaffected solid on the other end of the equation then you do not count it.

Jared Limqueco 3E
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Re: Pressure Rule

Postby Jared Limqueco 3E » Sun Jan 17, 2021 6:04 pm

I believe solids and liquids don't count, only gases.

Isabella Cortes 2H
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Re: Pressure Rule

Postby Isabella Cortes 2H » Sun Jan 17, 2021 6:06 pm

i believe that you should only look at the moles of gas since they are the ones that will be affected by the change in pressure.

David Jen 1J
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Re: Pressure Rule

Postby David Jen 1J » Sun Jan 17, 2021 6:15 pm

Only count moles of gas.

Sai Ramadas 1J
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Re: Pressure Rule

Postby Sai Ramadas 1J » Sun Jan 17, 2021 6:18 pm

For pressure, we only count the moles of gas on each side. The reaction will favor the side with less moles of gas.

Aliya Roserie 3I
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Re: Pressure Rule

Postby Aliya Roserie 3I » Sun Jan 17, 2021 6:29 pm

Remember we can only account this for gases, we exclude liquids and solids.

Naomi Hernandez-Ramirez 1J
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Re: Pressure Rule

Postby Naomi Hernandez-Ramirez 1J » Sun Jan 17, 2021 6:59 pm

I believe that liquids and solids don't count and we only do the moles of gases

Danielle DIS2L
Posts: 90
Joined: Wed Sep 30, 2020 9:38 pm

Re: Pressure Rule

Postby Danielle DIS2L » Sun Jan 17, 2021 10:53 pm

We only consider the moles of gases, not the solid and liquid ones


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