Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: 1stplace on April 03, 2008, 01:49:01 AM
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I read from two different sources saying contradicting things. So, I am left confused. One source says that catalyst only affects the rate constant and does not affect the order of the reaction. but the other sources says that it affects the order.
Which is correct?
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No
Read only good sources!
http://en.wikipedia.org/wiki/Chemical_equilibrium
http://en.wikipedia.org/wiki/Catalysis
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Hi AWK, it says that "Catalysts cannot make energetically unfavorable reactions possible — they have no effect on the chemical equilibrium of a reaction because the rate of both the forward and the reverse reaction are equally affected (see also thermodynamics)."
so, because it can not affect the equilibrium equation, it can't affect the rate constant? Is this what you mean? Or is there another part in the article?
If you are referring to the equilibrium equation, can't it still be in the rate equation because in the equilibrium equation, the top and bottom cancel out. Thus, if the equilibrium is equal to [X][Y]/[C][Y]=>[X]/[C], where [Y] is the catalyst, it can still include the catalyst but it is just that the top and bottom cancel.
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Ahh, Kinetics, otherwise known as "My university blind spot".
I'd love to help... Thank god I don't have to teach it!
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they have no effect on the chemical equilibrium of a reaction because
the rate of both the forward and the reverse reaction are equally affected
t can't affect the rate constant?
They affect rate constants in both direction but equilibrium remains unchanged
Even if you include catalyst in both nominator and denominator it cancels out in the final equation
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so, because it can not affect the equilibrium equation, it can't affect the rate constant? Is this what you mean? Or is there another part in the article?
Do you know about Arrhenius equation? r = Ae^(-Ea/RT)
Since a catalyst provides an alternative route for the reaction which has LOWER activation energy(Ea), hence the rate is affected, is this what you are referring about?
And also, it is possible for catalyst to be in the rate equation.
For example nucleophilic addition of HCN with NaCN catalyst to ethanal.
The rate equation would be r = k [ethanal][NaCN]
Hence, catalyst does affect the rate constant.
Whereas catalyst doesn't affect equilibrium constant since both forward and backward reactions are equally affected so the resultant effect is like being 'cancel out'
Kelvin ;D