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Homework Help: Aqueous and gaseous elements and compounds?

  1. May 10, 2009 #1
    1. The problem statement, all variables and given/known data
    Predict the sign of ΔS(sys) for each of the following processes:
    a) Zn(s)+2HCl(aq)-->H2(g)+ZnCl2(aq)
    b) CH3CH2CH3(g)+5O2(g)-->3CO2(g)+4H2O(l)

    Also, i'm not sure but when we're evaluating questions like these, do we count the number of moles only of solids, aqueous and gaseous elements and compounds?

    2. Relevant equations

    3. The attempt at a solution
    The first one, ΔS is POSITIVE but i'm not sure why though because 3 moles reactants-->2 moles reactant (should be more ordered (negative)...) thanks.
  2. jcsd
  3. May 14, 2009 #2
    Re: Entropy

    The states are changing from more ordered ones (solid) to less ordered ones (gas) overall. This is an increase in entropy.
    Hope that helps, I'm pretty confident its right.
  4. May 14, 2009 #3


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    Science Advisor
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    Gold Member

    Re: Entropy

    Out of solids, liquids, and gases, one state typically has a very large molar entropy that dominates over the others.
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