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    Q.

    Place the following in order of boiling point (lowest first). Explain your answer.

    HF NaF F2 Ne Al2O3


    I need help please...

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    (Original post by ArsenalTFX)
    Q.

    Place the following in order of boiling point (lowest first). Explain your answer.

    HF NaF F2 Ne Al2O3


    I need help please...

    Thanks
    Consider each molecule in turn.

    HF
    Structure: Simple molecule
    Bonding: Van der Waals forces, hydrogen bonding, induced permanent dipoles

    NaF
    Structure: Ionic lattice
    Bonding: Ionic bonding between molecules, Van der Waals

    F2
    Structure: Simple molecule
    Bonding: Van der Waals forces, induced temporary dipoles

    Ne
    Structure: Simple molecule
    Bonding: Van der Waals forces

    Al2O3
    Structure: Ionic lattice
    Bonding: Van der Waals

    Ionic lattices have highest boiling points, then simple molecular.

    So either Al2O3 or NaF has the highest boiling point.
    It must be Al2O3 since, this has a higher electron number => greater number of VDW forces and the charges on the ions are greater, so stronger ion-ion dipole. NaF has the 2nd highest boiling point.

    Next comes the simple molecules; HF, F2, Ne
    Hydrogen bonding is stronger than VDW, therefore HF has the 3rd highest boiling point, since HF displays hydrogen bonding. F2 has the 4th highest boiling point, since fluorine is diatomic, so has VDW intermolecular forces as well as induced temporary dipoles. Ne therefore by elimination has the lowest boiling point.

    So in order of boiling point (lowest first)
    Ne, F2, HF, NaF, Al2O3
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    great explanation WM .... only you wrote the answer the wrong way round!
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    (Original post by charco)
    great explanation WM .... only you wrote the answer the wrong way round!
    ah, so i did.
    Thanks.
 
 
 
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