The most stable at higher pressures

Discussion in 'Chemistry' started by chikis, Sep 9, 2012.

  1. chikis Registered Senior Member

    Messages:
    328
    In which of the following reactions would you expect the product to be more stable at higher pressures? I. 2SO2(g)+O2(g) ----->
    <---- 2SO3(g)
    II. N2(g)+3H2(g) ----->
    <---- 2NH3(g)
    III. H2(g)+I2(g)---->
    <----2HI(g)
    IV. N2(g)+O2(g)---->
    <-----2NO(g)
    The wording of the question is a bit confusing. What do they mean by "the products being stable"? I would have loved it if the question goes like this, " In which of the following reaction would the forward or backward reaction be favoured at higher pressures"? I think I will not be able to answer this question untill am able to understand what they mean by, " products to be more stable at higher pressures".
    Any help will be appreciated greatly. Thanks!
     
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  3. chikis Registered Senior Member

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    Let me understand it this way:
    let's look at this way, for example in the chemical reaction II. N2+3H2 are the reactant or backward reaction while NH3 is the product or forward reaction. By asking of the reaction in which the product is going to be more stable at higher pressure, they are actually trying to know the reaction in which the forward reaction will be favoured.

    If that be the case, using Le-Chatellia principle, when gases react and gasous product/s is/are formed, the equilibrum position shift to the side with less number of moles.
    In reaction II. 4 moles of the reactants produce only 2 moles of NH3. Therefore, the equilibrum position will move from left to right making the production of NH3 the product to be stable. Looking at all the equation from I. to the end IV, is only in II. that that can happen. How about that?
     
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  5. arauca Banned Banned

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    4,564


    As for me 2 SO2 -+ O2---> 2 SO3 and the what is meant higher pressure ( How high )
     
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  7. chikis Registered Senior Member

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    328
    I think I have actually gotten the answer to the question. What they mean by the product being stable here means the one that it production will be costant at higher pressure. High pressure favours the side with less number of mole. Therefore I and II carries the answer to the question.
    The authors of the question were so dumb that they provided a wrong answer to the question by choosing I and III as the answer to their question. Anyway, I don't blame them as such, it could be typo error. What do you think?
     
  8. Trippy ALEA IACTA EST Staff Member

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    I and II are what I would expect the correct answers to be. As they are written, there are fewer moles of products than there are reactants, so Le Chatelier's principle suggests that increasing the pressure on these two systems will drive the equilibrium point in favour of the products to counteract the increases in pressure. I would expect increasing the pressure to have little, if any, effect on reactions III & IV because there are as many moles on the reactant side as there arfe on the product side.
     
  9. chikis Registered Senior Member

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    328
    Thank you for that observation!
     

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