3F. 5C

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3F. 5C

Postby JamieVu_2C » Tue Oct 29, 2019 8:53 pm

Suggest, giving reasons, which substance in each of the following pairs is likely to have the higher normal melting point
(Lewis structures may help your arguments):
(c) CHI3 or CHF3.

How does CHI3 have a higher melting point than CHF3 when CHF3 is more polar due to the F atom?

Justin Vayakone 1C
Posts: 110
Joined: Sat Sep 07, 2019 12:19 am

Re: 3F. 5C

Postby Justin Vayakone 1C » Wed Oct 30, 2019 5:33 pm

The size of the atoms largely contribute to the melting point of molecules. Fluorine may have stronger dipole-dipole attraction than Iodine, but that difference in electronegativity is trumped by the difference in size. Iodine is bigger than Fluorine, meaning more electrons and stronger London Dispersion Forces, so CHI3 actually has stronger intermolecular forces and a higher melting point than CHF3.

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