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Homework Help: Molecule - Polar or Non Polar?

  1. Feb 1, 2009 #1
    1. The problem statement, all variables and given/known data

    Determine whether each of the following molecules is polar or nonpolar.
    (Please note that lone pairs have been omitted for simplicity!)

    I - C - I

    2. Relevant equations

    Electronegativity, Polarity, Dipole moments

    3. The attempt at a solution

    It seemed to me like the C and I have the same polarity so the net dipole would have been zero, but the answer says the molecule is Polar. Why?

    Thanks for any help with the explanation! =)

  2. jcsd
  3. Feb 1, 2009 #2
    No, I is more electronegative than C because it is halogen.

    Note that the molecule adopts a tetrahedral shape. Either way, the dipole moment will go from the in-between of 2 C-H bonds to the in-between of 2 C-I bonds
  4. Feb 1, 2009 #3
    I'm sorry I don't get the last part of what you said. Do you think you could explain? =)

  5. Feb 1, 2009 #4
    Read dichloromethane in http://dwb4.unl.edu/Chem/CHEM869E/CHEM869ELinks/www.uis.edu/7Etrammell/organic/introduction/polarity.htm [Broken]
    Last edited by a moderator: May 4, 2017
  6. Feb 1, 2009 #5
    Great link! Also, I have another question:

    1) H3COCH3 H3CCH2CH3

    It says that the first one has the higher boiling point because of dipole forces. Is there some sort of greater dipole between the C and the O? It looks like it might cancel out though?

    2) C2H5OH CH3OCH3

    Here, would it be the second one, on account of a great mass, London Dispersion forces being the factor that increases the boiling point?

    Thanks! I'm starting to get this I think!! =)

  7. Feb 1, 2009 #6
    And wait, doesn't it say that the tetrahedral would cancel out???


    The top image show the bond electron density and the bottom image the molecular dipole

    m = 0 D"
  8. Feb 1, 2009 #7
    1) Yes, permanent dipole permanent dipole (H3COCH3) is stronger than London Dispersion force (H3CCH2CH3).

    2) BP should be C2H5OH (stronger hydrogen bonding) > CH3OCH3 (pdpd)

    Yes, CCl4 would be a non-polar molecule.
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