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Author Topic: Molar mass affecting boiling point question  (Read 833 times)

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Shadow

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Molar mass affecting boiling point question
« on: January 15, 2013, 12:17:36 AM »

Why does the molar mass affect the boiling point?
I know its a common thing that "more massive" molecules have bigger boiling points, but how is this explained from the perspective of inter-molecular forces? I know how the London forces work, but I can't combine it with the molar mass  :'(. Help would be appreciated!
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Dan

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Re: Molar mass affecting boiling point question
« Reply #1 on: January 15, 2013, 01:23:23 AM »

Hint: What makes the magnitude of London dispersion forces larger?
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Shadow

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Re: Molar mass affecting boiling point question
« Reply #2 on: January 15, 2013, 02:44:50 AM »

That's what I was asking. I know the dipoles mechanism, but why and how does it change with the change of molar mass?
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Dan

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Re: Molar mass affecting boiling point question
« Reply #3 on: January 15, 2013, 03:48:05 AM »

Here is a simplification: If I gave you a big piece of velcro and a small piece of velcro, which would you expect to stick more strongly to a furry surface?

See also: http://en.wikipedia.org/wiki/London_dispersion_force
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Shadow

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Re: Molar mass affecting boiling point question
« Reply #4 on: January 15, 2013, 04:07:29 AM »

The part with the surface area in understandable.
Quote
London forces become stronger as the atom or molecule in question becomes larger. This is due to the increased polarizability of molecules with larger, more dispersed electron clouds.
I heard about polarizability in ionic compounds, it makes them less polar. How does it affect molecules?
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