How Do Different Stresses Affect a Chemical Equilibrium Reaction?

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Discussion Overview

The discussion centers on the effects of various stresses on the chemical equilibrium of the reaction N2(g) + O2(g) <--> 2NO(g), particularly in relation to temperature changes, pressure variations, catalyst addition, and the introduction of inert gases. Participants explore theoretical implications and reasoning behind these effects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants suggest that decreasing temperature will shift the equilibrium to the left, while others express uncertainty about the effects of pressure changes, particularly when the pressure is decreased.
  • It is proposed that adding a catalyst will have no effect on the equilibrium position, as it accelerates both the forward and reverse reactions equally.
  • Some argue that removing NO will shift the equilibrium to the right due to decreased product concentration.
  • There is a claim that adding argon gas will not change the equilibrium position, as it does not participate in the reaction, while others contest this by discussing the implications of pressure changes.
  • One participant raises a question about the effects of increasing pressure in the context of a different reaction (N2 + 3H2 <--> 2NH3), suggesting that it would shift to the right to relieve pressure.
  • Another participant asserts that adding a nonreactive gas increases total pressure but does not affect the concentrations of reactants or products, leading to a debate about the role of inert gases in equilibrium.

Areas of Agreement / Disagreement

Participants express differing views on the effects of inert gases and pressure changes on equilibrium, with no consensus reached on these points. Some agree on the effects of temperature and catalyst addition, while others challenge these assertions.

Contextual Notes

Some claims rely on specific assumptions about the nature of the gases involved and the conditions of the reaction, which may not be universally applicable. The discussion also highlights the complexity of equilibrium expressions and the role of partial pressures.

Who May Find This Useful

This discussion may be of interest to students and educators in chemistry, particularly those exploring the principles of chemical equilibrium and the effects of various stresses on reaction systems.

lapo3399
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1.
Given the equilibrium reaction:
N2(g) + O2(g) <---> 2NO(g) deltaH=180kJ mol-1
State the effect of each of the following potential stresses on the system:
A) Temperature is decreased
B) The pressure of the container is decreased, keeping volume constant
C) A catalyst is added
D) NO is removed as it forms
E) Argon gas is added to the container

2.
A) A shift to the left will occur, considering the enthalpy of reaction.
B) Not sure about this one, as the only way to accomplish this is to remove particles from the container. My best guess is that, assuming an equal quantity of reactants vs. products is removed, there will be no shift as the ratio of moles of reactant to moles of product is 1:1.
C) No change, as the catalyst will catalyze both the forward and reverse reactions equally.
D) Shift to the right, as product collisions decrease as NO is removed.
E) No change, as the argon will increase the total pressure, but will not react in collisions.
 
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Your answers are correct. Also, choice B is poorly written and this should probably be brought to the attention of the instructor.
 
Last edited:
Gokul43201 said:
For instance, addition of argon (at constant volume) to the reaction N2 + 3H2 <--> 2NH3, will produce a shift to the right.

Why is this? Argon is inert and the partial pressures of the reactants and product will remain unchanged.
 
Yikes! You are absolutely right. I don't know what I was thinking!

<editing above post to minimize miscommunication>
 
post edited to remove error
 
Last edited:
Plastic Photon said:
Why is this? Argon is inert and the partial pressures of the reactants and product will remain unchanged.

Well you are talking about stressing the equilibrium point. if the equation increases pressure if it goes to the right, and you increase the pressure the equation will go towards relieving this pressure and will go to the left. and I'm sure about this answer.
And if the equation increases temperature as it goes to the right, then a decrease in temperature will goes it to increase the temperature even more. cause it has to maintain its stability.
 
eaboujaoudeh said:
Well you are talking about stressing the equilibrium point. if the equation increases pressure if it goes to the right, and you increase the pressure the equation will go towards relieving this pressure and will go to the left. and I'm sure about this answer.
And if the equation increases temperature as it goes to the right, then a decrease in temperature will goes it to increase the temperature even more. cause it has to maintain its stability.

You can see for youself why this cannot possibly be true if you substitute the concentration of the argon into the equilibrium expression. The same term will appear in the numerator and denominator of the equilibrium expression. Cancelling gives you an equilbrium expression that is only dependent upon the concentrations of products and reactants. Argon is neither reactant nor product.
 
ok then. what happens if i increase the pressure in the container without adding or changing anything else?
 
The answer to "B" applies to both lowering and raising the pressure.
 
  • #10
N2 + 3H2 <--> 2NH3 i meant for this equation sorry. if i increase pressure here i would get the equation shifting towards the right to relieve the pressure right? how do u increase pressure? well u induce a nonreactive gas! this gas increases the overall pressure in the container thus it stresses the equation and causes it to move towards the pressure releasing side.
 
  • #11
Absolutely.
 
  • #12
thus my quote was right ! i was quoting plastic photon who said that adding a nonreactive gas to an equation won't alter its' equilibrium pt.my answer is that it will !
 
  • #13
An addition of inert gas changes the total pressure, however an addition of reactive gas changes both the total pressure and the partial pressure of the reactants and products.
 
  • #14
chemisttree said:
Absolutely.

Sorry, I should have replied "Absolutely not."


Will increasing the pressure of a vessel with an inert gas change the concentration of either the reactants or products?
 
  • #15
woops..i guess you're right. adding an inert gas will have no effect on the concentration of products and reactants..ssorryy
 

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