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Homework Help: Intermolecular Forces

  1. Oct 2, 2008 #1
    what is the strongest intermolecular force, dipole-dipole, london dispersion, or hydrogen bonding.
    also, how do you know if a molecule is dipole-dipole, london dispersion, or dydrogen?
  2. jcsd
  3. Oct 2, 2008 #2
    metallic bonds maybe?
  4. Oct 2, 2008 #3
    Any book or site will give you a good answer to your question, I'm just going to be short and sweet to the point with some old notes

    Typically in intermolecular forces hydrogen bonds are the strongest they range from 10 to 40kjmol^-1. London dispersion or dispersion if you wanna call that are the weakest, all molecules have ld. H-bonds are usually hydrogens bonded to F, O, N. Its not an actual bond, just a bridge. For ion-dipole, you get an ion interacting w/ permanent dipoles. Think of acetic acid (CH3COOH). O in CH3COOH has partial - charge, while C, guy below has a partial + charge.

    Polarizability is also important b/c it describes electrons shifting. Butane has greater tendencies for induced polarizability than branched chains.
    Last edited: Oct 2, 2008
  5. Oct 2, 2008 #4
    when an acid is dissolved in water it ionizes and thereby adds protons to the water. when a piece of metal is placed into the acidic water the metal atoms ionize and replace the protons which bubble out as hydrogen. presumably therefore they must form a stronger bond with the water than the protons do. what sort of bond do the metal ions form with the water molecules?
    Last edited: Oct 2, 2008
  6. Oct 4, 2008 #5
    what type of intermolecular force is strongest present in CHF3?
    -hydrogen bonding

    Is it dipole-dipole?

    Also which compound exhibits hydrogen bonding as its strongest intermolecular force?
    CH3OH or CH2F2

    is it CH3OH? CH2F2 doesn't have a hydrogen bond does it, since the hydrogens and the fluorines are only bonded with carbon?
    Last edited: Oct 4, 2008
  7. Oct 5, 2008 #6
    well i dont know the answer to your questions but that wont stop me from responding.

    hydrogen bonds with carbon with a covalent bond while fluorine bonds ionicly. each fluorine pulls a single electron off the carbon atton. so the carbon atom is surrounded by fluorine atoms whose valance shells are completely filled up. this is similar to the electronic configuration of noble gases. I would assume that is why such carbon compounds have 'nonstick' properties.

    obviously you still have ionic intermolecular forces.

    I really dont see any reason why hydrogen bonds wouldnt form with the fluorine atoms but I dont really know enough about it to say one way or the other.
  8. Oct 5, 2008 #7
    btw, you know it only just occurred to me why larger molecules are liquids at higher temperatures. its because larger molecules have lower velocities at any given temperature than smaller molecules. I always thought it was because the intermolecular forces were stronger.
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