catalyst

[Dencology]

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does catalyst increase the forward rxn more than the reverse rxn? also, does catalyst react chemically during the course of the rxn or not?

 

[Tina324]

a catalyst reacts chemically.
a catalyst does NOT change the Keq of the reaction and therefore doesn't make the forward reaction go faster than the reverse (or vice versa). The forward and reverse reactions still remain in the same proportion to each other.

hope that helps!

 

[flycd05]

the overall rate for forward and reverse reactions increases (but still in the same proportion as mentioned above) b/c of the lower activation energy - so the SPECIFIC rate constant, reaction mechanism are also changed. however the equilibrium is not shifted in any way since the only thing that can affect the Keq is temperature.

 

[Dencology]

Tina and flycd05, thanks.

 

[Dencology]

Tina and flycd05, i have another question to ask you:

in stochiometry problems, when we are ask to see which is the limiting rxn and we are given lets say 100 grams of H and 100 grams of O2, and we want to find the # of moles that is in 100g, do we divide 100 by 2 go get the number of moles of H or by 1 also, for O2 do we divide by 16g or 32g?
i always mix this up! thanks.

 

[Tina324]

i think it depends on what you are given the weight of...if it says 100g of H then u divide by 1 BUT if it says 100g of H2 then u divide by 2.

 

[flycd05]

yeah i think it depends on the reaction. if you have for example: CH4 + 2O2 --> CO2 + H2O

to find the number of moles of O2 u would divide 100g by 32g...so i think it does depend on the reaction given.

someone correct me if i'm wrong