Changing Pressure

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Maya_Peterson1C
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Changing Pressure

Postby Maya_Peterson1C » Fri Jan 11, 2019 9:00 pm

Can someone clarify why there needs to be a change in volume for there to be a change in pressure of a reaction in equilibrium?

Samantha Ito 2E
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Joined: Fri Sep 28, 2018 12:29 am

Re: Changing Pressure

Postby Samantha Ito 2E » Fri Jan 11, 2019 9:26 pm

Decreasing the volume of a contained gas will increase its pressure, and increasing its volume will decrease its pressure.

Chem_Mod
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Re: Changing Pressure

Postby Chem_Mod » Fri Jan 11, 2019 10:11 pm

Boyle's Gas Law (which we did not yet cover) says that pressure and volume are inversely related. Therefore, increasing the volume results in a decrease of pressure while a decrease of volume results in an increase of pressure. when an inert gas is added to the system in equilibrium at constant volume there will be no effect on the equilibrium. Adding an inert gas (such as a noble has or N2) at constant volume DOES NOT effect the equilibrium. Can anyone give me a good explanation of why?

Simran Rai 4E
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Re: Changing Pressure

Postby Simran Rai 4E » Fri Jan 11, 2019 11:12 pm

Adding an inert gas wouldn't affect the equilibrium because the concentrations of the reactant and product would remain the same, meaning there would be no change in the equation.

MichelleTran 1I
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Re: Changing Pressure

Postby MichelleTran 1I » Sat Jan 12, 2019 12:06 am

Pressure and volume have an inverse relationship, therefore if you want to change the pressure within the reaction you have to change the volume of the container. To increase the pressure, volume must decrease, so that particles within the container are more squished together, creating greater pressure and vice versa. Adding and inert gas does not affect the reaction in any way because the gases are so stable that they will not react to any of the reactants or products and therefore does not change the concentrations of either nor does it change the equilibrium constant.

Henry Dudley 1G
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Re: Changing Pressure

Postby Henry Dudley 1G » Sat Jan 12, 2019 2:55 pm

Simran Rai 4E wrote:Adding an inert gas wouldn't affect the equilibrium because the concentrations of the reactant and product would remain the same, meaning there would be no change in the equation.


But if the volume changes, how is there not a change in the concentration if the concentration is affected by volume?

Kathryn 1F
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Joined: Fri Sep 28, 2018 12:19 am

Re: Changing Pressure

Postby Kathryn 1F » Sat Jan 12, 2019 3:47 pm

Henry Dudley 1G wrote:
Simran Rai 4E wrote:Adding an inert gas wouldn't affect the equilibrium because the concentrations of the reactant and product would remain the same, meaning there would be no change in the equation.


But if the volume changes, how is there not a change in the concentration if the concentration is affected by volume?


The volume refers to the container (eg a 1L box and you decrease it to a .5L box). Adding an inert gas to a 1L box will not change the volume of that box.
Say you have 1 mole/L of NH3 in a 1L box. Adding 5 moles of Helium will not affect the concentraion of NH3, which would still be 1 mole/L.


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