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3F.1 C

Posted: Tue Nov 19, 2019 3:40 pm
by Lauren Haight 1E
Why does CHI3 have a higher melting point than CHF3? I would guess that dipoles are stronger in CHF3 due to F's high electronegativity, but this is not the case. Can someone please explain?

Re: 3F.1 C

Posted: Tue Nov 19, 2019 3:43 pm
by Lauren Haight 1E
Because I is larger than F, does molecular size trump intermolecular interaction when determining melting points?

Re: 3F.1 C

Posted: Tue Nov 19, 2019 3:53 pm
by Mashkinadze_1D
The induced-dipole-induced-dipole forces in the molecule with iodine are so much higher than the one with fluorine that it cancels out the stronger dipole due to the large difference in the amount of electrons between the two elements. In certain cases a stronger dipole moment would create stronger IM forces, but when the amount of electrons is so drastically large the increased polarity is outweighed. Hope this helps!

Re: 3F.1 C

Posted: Tue Nov 19, 2019 3:55 pm
by Aman Sankineni 2L
Molecular size determines intermolecular interaction strength. Since Iodine is a larger atom than Fluorine, it has stronger intermolecular strength and therefore a higher melting point.