reaction kinetics question

I'm really having trouble with this question, can someone help me with an explanation?

Is it possible to vary the factors of concentration, surface area, and temperature in a way that would prevent a reaction from happening? explain your answers in terms of collisions.

Will catalysts always speed up reactions?

thanks in advance

Reply 1

vinny221

11

I'm sure if you either/or lowered the concentration of reactants, lowered the temp and surface area sufficently, you could prevent a reaction happening. A catalyst will always speed up reactions except for equilibrium systems when it will speed up the rate of the forward and back reactions hence the product yield isnt affected.

less conc=less collisions due to less reactants
less sa means it's harder for reactants to overcome their acitvation energy as they are in larger sizes.
less temp means less kinetic energy so less chance of collisions

temp can be a bit funny with biological molecules such as enzymes/proteins. too high a temp will denature the proteins permanently so the reaction stops/no collisions. too low a temp means less collisions as the enzymes/proteins have no kinetic energy.

Reply 2

steve2005

17

intr3pid

I'm really having trouble with this question, can someone help me with an explanation?

Is it possible to vary the factors of concentration, surface area, and temperature in a way that would prevent a reaction from happening? explain your answers in terms of collisions.

Will catalysts always speed up reactions?

thanks in advance

Simply lowering the concentration will not stop a reaction - it will slow it but not stop. For a reaction to take place the particles must collide - so to stop a reaction freeze it.

Reply 3

Comp_Genius

4

intr3pid

I'm really having trouble with this question, can someone help me with an explanation?

Is it possible to vary the factors of concentration, surface area, and temperature in a way that would prevent a reaction from happening? explain your answers in terms of collisions.

Will catalysts always speed up reactions?

thanks in advance

I think theoretically you can stop the reaction in the first and the third instance. Reaction would stop if both solutions are infinitely dilute so the probability of collision between two particles is zero, similarly at absolute zero, the particle by definition, has no kinetic energy, therefore the two particles will not collide. Although it is not possible to reach absolute zero, as by Heisenberg's Principle, since you have determined the exact momentum of the particle (mv = 0), you cannot know where the particle is.

just eavesdropping!

I believe that there are such things as negative catalysts whose role is to slow a reaction down. Could be useful in a process where there are two competing reactions and you don't want one of them to occur.

a sort of inhibitor?

exactly

reaction kinetics question

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