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September 21, 2019, 02:52:40 pm

### AuthorTopic: Help: Adding inert gases Vs Equilibrium?  (Read 883 times) Tweet Share

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#### We Want Peace.

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##### Help: Adding inert gases Vs Equilibrium?
« on: November 09, 2008, 12:52:23 pm »
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:idiot2:

Adding inert gased increases the pressure of all species in a reaction.
However, i wonder why it does not affect the position of the equilibrium system?.
Can anyone explain to me please'''

#### Collin Li

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##### Re: Help: Adding inert gases Vs Equilibrium?
« Reply #1 on: November 09, 2008, 01:16:40 pm »
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:idiot2:

Adding inert gased increases the pressure of all species in a reaction.
However, i wonder why it does not affect the position of the equilibrium system?.
Can anyone explain to me please'''

The part in bold is incorrect. It increases the total pressure of the system, but it does not affect any other species' partial pressure (1). Hence, it does not affect the other species' concentration (2), and consequently, the system's reaction quotient.

Explaining (1):

Consider the system with gas $A$ and $B$.

$P_{TOT} = P_A + P_B$

Now, insert inert gas $G$

Now,  $P_{TOT} = P_A + P_B + P_G$

Hwoever, the individual partial pressures, $P_A$ and $P_B$ have not changed.

Explaining (2):

Using the ideal gas equation:

$pV = nRT$

$\implies p = \frac{n}{V}RT$

$\implies p = cRT$

$\implies c = \frac{p}{RT}$

Since $R$ and $T$ are constant for any given temperature, then if $p$ does not change (as explained above), therefore $c$ does not change.

Hence, if the system is at equilibrium $Q$ (reaction quotient) does not change, and so it remains that: $Q=K$. The system stays in equilibrium.

#### We Want Peace.

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##### Re: Help: Adding inert gases Vs Equilibrium?
« Reply #2 on: November 09, 2008, 01:47:48 pm »
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ok.I see
But what if they say adding inert gases into a sealed reaction vessel?( i.e. the volume of the vessel remain the same)?

#### bucket

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##### Re: Help: Adding inert gases Vs Equilibrium?
« Reply #3 on: November 09, 2008, 01:51:16 pm »
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I think he's saying it increases the overall pressure in the system, but does not effect the pressures exerted on the individual gasses. (Which is what I assume partial pressure is)
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#### Mao

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##### Re: Help: Adding inert gases Vs Equilibrium?
« Reply #4 on: November 09, 2008, 09:10:27 pm »
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I think he's saying it increases the overall pressure in the system, but does not effect the pressures exerted on the individual gasses. (Which is what I assume partial pressure is)

the pressure on each individual gas does increase [inert gas particles bumping into reactants/themselves]

however, the pressure exerted by the individual gases do not change [i think]
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#### Pandemonium

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##### Re: Help: Adding inert gases Vs Equilibrium?
« Reply #5 on: November 09, 2008, 09:35:34 pm »
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I think he's saying it increases the overall pressure in the system, but does not effect the pressures exerted on the individual gasses. (Which is what I assume partial pressure is)

the pressure on each individual gas does increase [inert gas particles bumping into reactants/themselves]

however, the pressure exerted by the individual gases do not change [i think]

lol wrong word emphasis, but yes. the partial pressures by the individual gases do not change, thus teh chances that reacting molecules bump into each other remain the same (assuming the volume remains the same).
yes, there will be more collisions. however, there won't be an increase in successful/fruitful collisions because the insertion of inert gases which are as the name suggests, inert, won't participate in the reaction itself..