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Boiling point and connection distance of the elements

  1. Jul 12, 2018 #1
    1. The problem statement, all variables and given/known data
    Explain the following order of the boiling point (° C)

    HF (19.5)> HCl (-85.1) <HBr (-66.8) <HI (-35.4)

    b) Explain the following order of connection distance (pm):

    HF (92) <HCl (127) <HBr (141) <HI (161)

    2. Relevant equations

    3. The attempt at a solution
    a) HF does hydrogen bond, and the others make ionic linking.
    b) The lower the atomic mass, the higher the boiling point
  2. jcsd
  3. Jul 13, 2018 #2
    This statement are wrong. (How?)
    And the others make covalent linking, not ionic (generally means electrovalent in some texts)

    You mean the intermolecular one, that too in an aqueous solution
    Last edited: Jul 13, 2018
  4. Jul 13, 2018 #3
    How does the electronegativity of the halogens & hence the H-X bond polarity change down the group?
  5. Jul 13, 2018 #4


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    Does not constitute an explanation, nor fits the data very well!
  6. Jul 14, 2018 #5
    Also, the statement
    makes it a bit ambiguous to know whether you've understood the concept of hydrogen bonding
  7. Jul 14, 2018 #6
    Yes, you're right! Ionic linkings are stronger! The best example is our kitchen salt, which your trying to separate stove, you can't because the boiling point of the NaCl is 900 °C and only in industries is possible to separate the sodium from the chlorine.

    Yes, I made a mistake.

    Yes, I don't know how to do this question.

    I didn't even internalized this subject. Could you recommend me a video lesson about this subject?
  8. Jul 18, 2018 #7
    To begin with, watch this:
  9. Jul 18, 2018 #8
    @José Ricardo After watching that, you can guess that these molecules get 'associated' (get closer together due to attractions) with each other. Think, how will that affect the boiling point?
  10. Jul 18, 2018 #9
    I find that working out answers to questions like these are best done by starting with a particle level description (i.e., what the atoms or molecules are doing). An excellent written source for that is Richard Feynman's Atoms in Motion.

    There are video's of Feynman informally talking about much of the material, like this and this. I find the text, though, more useful.
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