Kneecoal

10+ Year Member
Mar 2, 2009
870
0
Long Island, NY
Status
Pre-Dental
I know it's part of Le Chatelier's and all that, but I'm having trouble understanding why an increase in temp. favors and endothermic rxn and a decrease in temp. favors exothermic.

can someone please explain why?
 

Murl

10+ Year Member
7+ Year Member
Jan 16, 2008
212
1
Status
Dental Student
When a reaction is endothermic just place a little triangle symbolizing heat on the reactants side and treat it just like a reactant. So if we increased that reactant (heat) then it would drive the equilibrium to the right. Now think of an exothermic reaction, place the triangle on the right as a product, if we were to add heat to the reaction mixture we would be adding a product and driving the reaction back to the left. What if we took heat out of the reaction mixture and the reaction is exomthermic, we would then be removing a product and pushing the equilibrium to the right. If this doesn't make sense just say so and I will try and find another way to explain but you should try writing this out to see if it makes sense.
 
Jun 16, 2009
110
0
New York
Status
Podiatry Student
Its all about maintaining equilibrium. If you have the equation "A+B <==> C+heat" the reaction from right to left is obviously endothermic and left to right is exothermic. When you add heat it will shift the equation left, which is clearly the endothermic direction. Its the same principle as adding more C which which also shift the equation left.
 
OP
Kneecoal

Kneecoal

10+ Year Member
Mar 2, 2009
870
0
Long Island, NY
Status
Pre-Dental
ahhhh i get it now. the part about taking heat out like it's a product just helped me visualize it. thanks!
 

GOLF

7+ Year Member
Jul 6, 2009
179
3
Status
Dental Student
yeh destroyer has a good problem - jan2009 destroyer GC #38 - that has a good method that will def help you remember this concept.
 

joonkimdds

Senior Member
10+ Year Member
7+ Year Member
Jun 30, 2005
2,780
2
Status
Pre-Dental
'ex'o = 'ex'it of heat thus heat is released so it became cold.