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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: CossieG on October 24, 2013, 11:47:11 am

Title: Is this the correct way to describe how catalysts change the rate of a reaction?
Post by: CossieG on October 24, 2013, 11:47:11 am
A catalyst provides an alternative reaction pathway. It lowers the energy needed. By lowering it, more atoms have energy greater than the activation energy, and more collisions have greater energy than the activation energy, which increases the number of successful collisions and thus speeds up the reaction.
Title: Re: Is this the correct way to describe how catalysts change the rate of a reaction?
Post by: Alwin on October 24, 2013, 12:56:43 pm
A catalyst provides an alternative reaction pathway. It lowers the energy needed. By lowering it, more atoms have energy greater than the activation energy, and more collisions have greater energy than the activation energy, which increases the number of successful collisions and thus speeds up the reaction.

Seems solid enough, but you should remember to refer to time, increases the number of successful collisions in a given period of time.
eg 2 million collisions is certain greater than 1 collision, but what if the 2 million collisions were over 2 million years and the 1 collision was every second? (don't mean to make you feel bad, but examiners are picky like this)

My generic response would have been maybe something like this:

~ A catalyst provides an alternate reaction pathway with lower activation energy
~ Thus a greater proportion of particles have energy greater than the activation energy, Ea
~ Hence there is a greater proportion of collision are fruitful meaning a greater frequency of fruitful collisions
~ Therefore the rate of reaction increases

:)
Title: Re: Is this the correct way to describe how catalysts change the rate of a reaction?
Post by: lzxnl on October 25, 2013, 10:41:20 pm
I wouldn't have even said alternate reaction pathway.

I'd just say that the catalyst bonds to the reactants, weakening the bonds and thus reducing the activation energy of the reaction. Blah.

Title: Re: Is this the correct way to describe how catalysts change the rate of a reaction?
Post by: Alwin on October 26, 2013, 08:06:41 am
I wouldn't have even said alternate reaction pathway.

I'd just say that the catalyst bonds to the reactants, weakening the bonds and thus reducing the activation energy of the reaction. Blah.

We're allowed to make reference to intermediate bonds in VCE chem?

Asked my teacher way back and said it wasn't strictly on the course, only (intramolecular:) Ionic, covalent, polar covalent and metallic (though the crystalline structure is off the course) and (intermolecular:) dipoles, hydrogen, ionic and dispersion forces
At least that's what I think he said :P
Title: Re: Is this the correct way to describe how catalysts change the rate of a reaction?
Post by: Edward21 on October 26, 2013, 10:46:16 am
Seems solid enough, but you should remember to refer to time, increases the number of successful collisions in a given period of time.
eg 2 million collisions is certain greater than 1 collision, but what if the 2 million collisions were over 2 million years and the 1 collision was every second? (don't mean to make you feel bad, but examiners are picky like this)

My generic response would have been maybe something like this:

~ A catalyst provides an alternate reaction pathway with lower activation energy
~ Thus a greater proportion of particles have energy greater than the activation energy, Ea
~ Hence there is a greater proportion of collision are fruitful meaning a greater frequency of fruitful collisions
~ Therefore the rate of reaction increases

:)
When I read the question at the top, I said all these steps you stated almost word for word in my head before I came to your post!!
Title: Re: Is this the correct way to describe how catalysts change the rate of a reaction?
Post by: Alwin on October 26, 2013, 01:28:29 pm
When I read the question at the top, I said all these steps you stated almost word for word in my head before I came to your post!!

You know that they say, Great minds... like to quote silly overly clichéd sentences ;)