[pantsboy]

I was reading a chapter on Alkynes in my Org chem book when a question arose.  I read that traditionally acetelyene can be prepared from ethyelene as such:

Ethene  Acetylene + H₂
 :delta:(1150°C)

And the reverse of the reaction is hydrogenation while using a lindlar catalyst:

Acetylene + H₂ Ethene
    (cat. Lindlar)

Obviously the second reaction takes severly less energy to happen because of the catalyst lowering the activation energy.  But if the catalyst were removed and the equilibrium looked like such:

heat + Ethene  Acetylene + H₂

Since the reaction is endothermic, does this mean there would be a higher activation energy to produce acetylene than Ea of the reverse reaction (without use of catalysts)?   If you started with either just the products or reactants at STP which direction of the reaction would require more energy to complete?  It's been like 2 years since I learned about enthalpy/entropy so this might be really basic question, but I just can't remember how any of it works.

[renge ishyo]

The magnitude of the energy released going one way in the reaction is the exact same as the amount of energy that needs to be absorbed going the other way in the reaction. The effect of the catalyst is to make the reaction take place more rapidly; the catalyst does not change the energetics because it lowers the activation energy for both the forward and reverse reaction by the same amount.

[pantsboy]

oh duh 

sorry it's been a while since I've done any general chemistry.  that makes sense though.

i was confusing equilibrium stuff with thermochemistry by thinking that whatever side of the reaction is favored under STP must be due to the it's heat of formation.

thanks