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Aqueous and gaseous elements and compounds?

  • Thread starter lha08
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  • #1
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Homework Statement


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?


Homework Equations





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.
 

Answers and Replies

  • #2
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Zn(s)+2HCl(aq)-->H2(g)+ZnCl2(aq)
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.
 
  • #3
Mapes
Science Advisor
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Out of solids, liquids, and gases, one state typically has a very large molar entropy that dominates over the others.
 

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