Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    0
    ReputationRep:
    During a chemical reaction, an intermediate molecule can have an energy greater that that of the reactants. How does this energy get released as - e.g. a photon, etc.
    Offline

    1
    ReputationRep:
    Heat.
    • Thread Starter
    Offline

    0
    ReputationRep:
    Surely it does this by releasing a photon though. The only energy the two moleucles can give up is their kinetic energy. This can be used to promote electrons to different energy levels, etc. However, the intermediate product must now have 'give up' some energy. It can't just suddenly go faster (i.e. raise the temperaute) unless there is something to increase it's velocity - the only it could do this is to undergo conservation of momentum by ejecting a photon. However, this is of course not practical (or feasible), as the photon would have to have energy in the GeV's. However, does the intermediate product first releaase a photon (in which case electrons would have to decrease in nergy level (but where?)), adn then this photon is absorbed by the surroundings (and how exactly does infa-red etc increase the temperature? The photon could be absorbed and remitted, and there would be slight recoil, but I don't see how that would be enough).

    I'm not quite sure as to actually how the intermediate product releases it's excess energy.
    Offline

    1
    ReputationRep:
    (Original post by DeanK2)
    Surely it does this by releasing a photon though. The only energy the two moleucles can give up is their kinetic energy. This can be used to promote electrons to different energy levels, etc. However, the intermediate product must now have 'give up' some energy. It can't just suddenly go faster (i.e. raise the temperaute) unless there is something to increase it's velocity - the only it could do this is to undergo conservation of momentum by ejecting a photon. However, this is of course not practical (or feasible), as the photon would have to have energy in the GeV's. However, does the intermediate product first releaase a photon (in which case electrons would have to decrease in nergy level (but where?)), adn then this photon is absorbed by the surroundings (and how exactly does infa-red etc increase the temperature? The photon could be absorbed and remitted, and there would be slight recoil, but I don't see how that would be enough).

    I'm not quite sure as to actually how the intermediate product releases it's excess energy.
    No, their extra potential energy is converted into kinetic energy.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by TableChair)
    No, their extra potential energy is converted into kinetic energy.
    Firstly: what 'extra' potential energy are you talking about? (They are subject to no forces that can give them potential energy, nor where they ever subject to any, so the integral of -Fdx is most obviously zero.

    Even if the molecule did have energy, I am not disputing that it would need to be converted to kinetic energy in order to raise the temperature. however, the molecule does not think 'now would be a good time to increase my energy'. Instead, it must somehow release a particle (such as a phton), and take use of the conservation of momentum to achieve extra kinetic energy.

    Both of your above posts seem to give me the impression that you are merely stating what happens, without a mechanism - I clearly wan tot know HOW this happens.

    Thanks for the replies though.
    Offline

    1
    ReputationRep:
    An intermediate species will have a higher potential energy than the reactants. Of course it can have potential energy. Consider a system of point charges, the total potential energy of the system depends on the positions of the charges.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by TableChair)
    An intermediate species will have a higher potential energy than the reactants. Of course it can have potential energy. Consider a system of point charges, the total potential energy of the system depends on the positions of the charges.
    They can't. Think about it.

    EDIT: I mean the intermediate cannot, obviously your example is correct but not analogous
    Offline

    1
    ReputationRep:
    (Original post by DeanK2)
    They can't. Think about it.

    EDIT: I mean the intermediate cannot, obviously your example is correct but not analogous
    The intermediate is simply a different arrangement, so yes, it can.

    http://en.wikipedia.org/wiki/Reactive_intermediate

    A quote from there: "Their potential energy with respect to reactants or previous intermediates is defined to have a minimum of depth greater than available thermal energy arising from temperature, with an exact value RT, where R is gas constant and T is temperature."

    So they do have a different potential energy. Have you ever seen a graph of Energy (Potential enrgy) against reaction coordinate.

    How is my example not analogous
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Brussels sprouts
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.