Strength of Intermolecular Forces

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Strength of Intermolecular Forces

Postby JamieVu_2C » Tue Nov 19, 2019 1:22 am

Explain the trend in the boiling points of the hydrogen halides: HCl, -85 degrees Celsius; HBr, -67 degrees Celsius; HI, -5 degrees celsius. How would the boiling points depend on the forces of these molecules?

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Re: Strength of Intermolecular Forces

Postby AnvitaaAnandkumar_1B » Tue Nov 19, 2019 7:15 am

The boiling point of a molecule corresponds to the extent of Hydrogen bonding it undergoes - the greater the amount or strength of the hydrogen bonds, the higher the boiling point.

Camellia Liu 1J
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Re: Strength of Intermolecular Forces

Postby Camellia Liu 1J » Tue Nov 19, 2019 7:28 am

Hydrogen bonding occurs when a hydrogen atom is bonded to a small, strongly electronegative atom (specifically, N, O, or F) and is attracted to a lone pair of electrons on another N, O, or F atom.

It might be better to look at the strength of other intermolecular forces within these atoms, since HCL, HBr, and HI don't experience hydrogen bonding. We know that every molecule experiences LDF, and the higher the molar mass (the more electrons), the more polarizable and therefore the stronger its LDFs, so one way to answer the question could be to look at mass.

Kishan Shah 2G
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Re: Strength of Intermolecular Forces

Postby Kishan Shah 2G » Tue Nov 19, 2019 8:28 am

What Camellia said is correct. However, yesterday I came across the idea that HCl has a stronger bond than HBr since the bond length in HCl is shorter and stronger since Cl has a smaller atomic radii than Br does. How do you know which reasoning to use?

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