Le chatliers principles!!!!

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teefRcool

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Can someone explain this to me this is one section that kinda confuses me. Can someone please please explain how this works. going to the right going to left. either being endothermic or exothermic. If pressure goes up, volume goes up, temp goes up vice versa and etc. Thanks any help would be greatly appreciated.

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teefRcool said:
Can someone explain this to me this is one section that kinda confuses me. Can someone please please explain how this works. going to the right going to left. either being endothermic or exothermic. If pressure goes up, volume goes up, temp goes up vice versa and etc. Thanks any help would be greatly appreciated.

pv = nrt

what you do to one side of the equation you must to the other side......for example if p is doubled and v, n, and r and held constant then t must also double. If n, r, and t are held constant and p is double then v must be cut in half. I hope this helps a little.
 
Definition

LeChatlier's Principle - when a stress is applied to a system at equilibrium, the system will shift to relieve that stress and reestablish equilibrium

Endothermic reaction - requires energy (commonly heat) input for reaction to take place
Therefore:
Heat + A + B <---> AB
If you take away heat, reaction favors the reactants (left)
If you add heat, reaction favors the products (right)

Exothermic reaction- gives off energy in the process of chemical reaction
C + D <---> CD + Heat
If you take away heat, the reaction favors the products (right)
If you add heat, the reaction favors the reactants (left)

Now for the little bit more complex stuff: gas equilibrium

PV= nRT
Pressure and Volume are inversely related according to this universal equation

2A g + B g <---> AB g
If pressure is increased in this equation, volume will decrease and therefore system will shift to the side with the least number of moles of gas (right)

If pressure is decreased, volume will increase, and therefore the system will shift to the side with the most number of moles of gas (left)

Remember that equilibrium constant is specific for a system at a given temperature. No matter how much you change the volume, pressure, or concentration of a system, it will not change the equilibrium constant Keq (or Kc as some books call it). Only a change in temperature can change the value of Keq (Kc).
Whereas a change in pressure, volume, or concentration only changes the position of equilibrium (either left of right).

Hope that helps TeefRcool, if not let me know. If it still doesn't make sense, then consider investing in Schaum's outline of College Chemistry...it teaches you the basics of equilibrium from the beginning. Or you can invest in a set of cds called AudioOsmosis (put out by ExamKrackers), they do an excellent job of teaching chemistry basics and providing intuitive ways of understanding the matter (the price is steep though, $200 for the cds, consider borrowing them from a pre-med friend).

Peace,
IndDent
 
IndDent said:
Definition

LeChatlier's Principle - when a stress is applied to a system at equilibrium, the system will shift to relieve that stress and reestablish equilibrium

Endothermic reaction - requires energy (commonly heat) input for reaction to take place
Therefore:
Heat + A + B <---> AB
If you take away heat, reaction favors the reactants (left)
If you add heat, reaction favors the products (right)

Exothermic reaction- gives off energy in the process of chemical reaction
C + D <---> CD + Heat
If you take away heat, the reaction favors the products (right)
If you add heat, the reaction favors the reactants (left)

Now for the little bit more complex stuff: gas equilibrium

PV= nRT
Pressure and Volume are inversely related according to this universal equation

2A g + B g <---> AB g
If pressure is increased in this equation, volume will decrease and therefore system will shift to the side with the least number of moles of gas (right)

If pressure is decreased, volume will increase, and therefore the system will shift to the side with the most number of moles of gas (left)

Remember that equilibrium constant is specific for a system at a given temperature. No matter how much you change the volume, pressure, or concentration of a system, it will not change the equilibrium constant Keq (or Kc as some books call it). Only a change in temperature can change the value of Keq (Kc).
Whereas a change in pressure, volume, or concentration only changes the position of equilibrium (either left of right).

Hope that helps TeefRcool, if not let me know. If it still doesn't make sense, then consider investing in Schaum's outline of College Chemistry...it teaches you the basics of equilibrium from the beginning. Or you can invest in a set of cds called AudioOsmosis (put out by ExamKrackers), they do an excellent job of teaching chemistry basics and providing intuitive ways of understanding the matter (the price is steep though, $200 for the cds, consider borrowing them from a pre-med friend).

Peace,
IndDent

Awesome thanks a lot. So are there cases where you can have for examples
C + 2D <---> CD2 + Heat
and say what will happen if the pressure increases?
What will happen if volume increases?
is that a legit question by having heat in there also. cause your example was only endothermic and exothermic just saying if temp increases or decreases.
In the above question that i made can they ask you other info as well. Just curious thanks again.

I will try to get my hands on the osmosis also thanks.
 
teefRcool said:
Awesome thanks a lot. So are there cases where you can have for examples
C + 2D <---> CD2 + Heat
and say what will happen if the pressure increases?
What will happen if volume increases?
is that a legit question by having heat in there also. cause your example was only endothermic and exothermic just saying if temp increases or decreases.
In the above question that i made can they ask you other info as well. Just curious thanks again.

I will try to get my hands on the osmosis also thanks.


not that will be on the DAT but, th emost important parts of his law are to remember what way a reaction will be effected and maybe 1 question involving the formula pv=nrt
 
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