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Anyone want to check my chemistry quiz?

  1. Jul 1, 2008 #1
  2. jcsd
  3. Jul 1, 2008 #2

    Borek

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    Just skimmed - mostly OK, but at least one obvious error.
     
  4. Jul 1, 2008 #3
    Hmm. I finished this late last night. What's the obvious error?
     
  5. Jul 1, 2008 #4

    Borek

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    Sorry, you will not get it from me, unless you are ready to split your grade :wink:
     
  6. Jul 1, 2008 #5
    I can get it from you. This is an open-notes, open-book, open-person, take-home quiz. Just tell me the numbers, and I'll take a look at them.
     
  7. Jul 1, 2008 #6

    chemisttree

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    Well, for starters, one of your answers in 1) is wrong...
     
  8. Jul 1, 2008 #7

    Borek

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    Huh, missed that one.

    Which means there is still another mistake on the other end :wink:
     
  9. Jul 1, 2008 #8
    I don't see that one is wrong. Molecules with similar intermolecular forces will dissolve each other. Ionic compounds require polar molecules to dissolve. As far as I can tell, my answers reflect that. I also looked over the rest and didn't catch any error. I'll need a little more than there's just one wrong.
     
    Last edited: Jul 1, 2008
  10. Jul 1, 2008 #9

    Borek

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    Does CaO dissolve in water?

    What is boiling? When does the liquid boil and why?
     
  11. Jul 1, 2008 #10
    I don't see CaO and water in number one.

    The boiling point is when the vapor pressure equals or exceeds the atmospheric pressure.
     
    Last edited: Jul 1, 2008
  12. Jul 1, 2008 #11

    Borek

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    I never told there is CaO in number one, I just asked whether CaO dissolves in water. If CaO doesn't suit you, you may answer question about Na2O solubility :wink:

    That's correct. Now, why does the boiling point go up when you dissolve some substance?
     
  13. Jul 1, 2008 #12
    I would say CaO does dissolve in water. It's an ionic compound, and they require a polar molecule in which to dissolve. A water molecule is polar.

    The boiling point goes up because the vapor pressure is lowered. It requires more energy input to extract the molecules from the solution.
     
    Last edited: Jul 1, 2008
  14. Jul 2, 2008 #13

    Borek

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    No, this is chemistry, sometimes instead of dissolving things react or don't react.

    Correct. What will happen to the vapor pressure when you dissolve more substance?
     
  15. Jul 2, 2008 #14
    It'll lower more until it becomes saturated.
     
  16. Jul 3, 2008 #15
    Anyone else?
     
  17. Jul 3, 2008 #16

    Borek

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    You were given many hints. Have you checked what happens to CaO in water? Have you checked what is the chemistry of the only oxide present on the question sheet? Have you checked answers that deal with the changes in boiling point or vapor pressure?
     
  18. Jul 3, 2008 #17
    At the risk of sounding redundant, I already said I looked over the problems and didn't catch any mistakes. I took the first CHEM course over two years ago.
     
  19. Jul 7, 2008 #18

    chemisttree

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    You are making the (wrong) assumption that all inorganic compounds are purely ionic compounds and that they ionize completely (or mostly) in water. Calcium silicate (a major component in hydrated portland cement) is an example of an inorganic compound that has largely but not entirely ionic bonds. It does not dissolve appreciably in water. Calcium silicate is not on your list but I'll bet you can quickly find the compound that I was referring to.

    Hint: Bayer process
     
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