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Topic: La Chat. and voltaic cells  (Read 4195 times)

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Kong

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La Chat. and voltaic cells
« on: January 29, 2005, 05:17:38 PM »
This is long burning question.  

In an electrolytic cell.  Lets say:
Cu+  +  Zn  =  Cu  +  Zn2+    E = 1.1V   (Might be reverse reaction..any ways.)

This reaction is exergonic and according to La Chateliers Principle, if heat is applied the reaction should shift to reactants.  Yet in any electrolytic cell adding heat will cause the voltage to rise not drop.   I actually tested this and the Tech education teacher walked in and thought I was retarted.  The fact that I needed to test this to varify what was clear to him.  

Any thoughts?  

AS

Demotivator

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Re:La Chat. and voltaic cells
« Reply #1 on: January 31, 2005, 09:09:59 AM »
LeChatelier's principle only applies to a state at equilibrium.

When running a voltaic cell, you are not starting at equilibrium, so by the nernst equation E should rise with increasing T whether exergonic or not because In the initial stages [products] < [reactants]:

E = E(0) - (RT/nF)ln[products]^a/[Reactants]^b

When approaching stage near equilibrium, products may become greater than reactants. If that occurs then a  greater T causes a decrease in E.
 
« Last Edit: January 31, 2005, 09:10:54 AM by Demotivator »

Offline Mitch

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Re:La Chat. and voltaic cells
« Reply #2 on: January 31, 2005, 11:06:54 AM »
Good answer, I forgot about that.
Most Common Suggestions I Make on the Forums.
1. Start by writing a balanced chemical equation.
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pizza1512

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Re:La Chat. and voltaic cells
« Reply #3 on: February 03, 2005, 08:52:35 AM »
Why are batteries either acid or alkaline?.



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