AP Chemistry Question: Free energy.?

I am in a high school AP Chemistry course and the AP test is coming up. Our teacher has been giving us old AP test questions as homework to prepare. However there is one part of a question which even he couldn't understand. He gave it to us as extra credit. I would like to know if any of you understand it. It is an essay question. Here is the part none of us understand:

b) Some reactions that are predicted by their sign of delta G(standard state) to be spontaneous at room temperature do not proceed at a measurable rate at room temperature.

i) Account for this apparent contradiction.

ii) A suitable catalyst increases the rate of such a reaction. What effect does the catalyst have on delta G (standard state) for the reaction? Explain.

Thank you for any help you can offer.




Question involving Thermodynamics and Kinetic Molecular Theory.

3 Answers

  • Sam
    Lv 5
    1 decade ago
    Favorite Answer

    Do not confuse thermodynamics with kinetics. Since that deal with thermodynamics likes Gibb's free energy or equilibrium constant have nothing to do with how fast a reaction will proceed. It's is a little confusing, but when they say a reaction is spontaneous, it does not mean that it will go really fast, it just means that it will occur on its own. The only way to the determine how fast a reaction will react is through the rate constant and the concentration of reactants.

    ii) Again, kinetics has nothing to do with thermodynamics. delta G is determined by the difference in energy between the reactants and the products. The catalyst does not change this, the catalyst only lowers the activation energy and makes the reaction go faster.

    Source(s): Me
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  • H.
    Lv 4
    1 decade ago

    even though a reaction may be thermodynamically favourable, it does not necessarily mean it is kinetically favourable. for example, the conversion of diamonds into graphite actually has a relatively low delta H - it is thermodynamically favourable and releases heat. obviously, this does not happen so the conversion of diamond to graphite must be kinetically infavourable. this means that the reaction has a high activation energy i.e. it requires a lot of added energy to occur. so, thermodynamics only gives you half the story - you need to know the kinetics of a reaction as well. a catalyst increases the rate of a reaction by lowering the activation energy. honestly, i'm not sure what the effect is on the delta g, but i imagine it wouldn't change as a catalyst simply lowers the activation energy.

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  • cassin
    Lv 4
    3 years ago

    i recommend you do not too a lot in one day. it really is might want to be a touch new to you and also you do not opt to weigh down your self. also, i reccomend searching on youtube. type in "ap chemistry" as i have discovered some very efficient videos that fairly clarified dissimilar the added frustrating topics.

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