Textbook Questions

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Textbook Questions

Postby 805377003 » Sun Nov 15, 2020 5:01 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): (a) HCl HCl or NaCl NaCl; (b) C 2 H 5 OC 2 H 5 (diethyl ether) or C 4 H 9 OH (butanol); (c) CHI 3 or CHF 3 ; (d) C 2 H 4 or CH 3 OH .

Can someone explain this?

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Re: Textbook Questions

Postby Anthony_3C » Sun Nov 15, 2020 5:51 pm

This problem is testing your knowledge on intermolecular forces since the stronger this force, the higher the melting point of a molecule.
A) The difference in electronegativity is larger for NaCl, meaning a stronger ionic bond, so NaCl has a higher melting point.
B) Butanol (an alchohol) has hydrogen bonding, whereas diethyl ether only has London forces so it has a higher melting point.
C) The intermolecular force for both molecules is dipole-dipole force, but since F has a larger electronegativity, it pulls electrons from carbon towards it more, so CHF3 is more polar (the delta- of F is larger). Thus CHF3 is the answer.
D) CH3OH is also an alchohol, which means it has H bond, while C2H4 only has London fores. So it's the one.

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