Lecture Question CH4 and CCl4

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emilyyribarren1k
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Lecture Question CH4 and CCl4

Postby emilyyribarren1k » Wed Nov 11, 2020 1:52 pm

In Lavelle's slides from today's lecture it says methane (CH4) has a boiling point of -161 degrees celsius and tetrachloromethane (CCl4) has a boiling point of +77 degrees celsius, which is obviously much higher. I just want to double check that the reasoning I came up with for this difference is correct.

Cl is more polarizable than H because it is a larger atom and holds onto its electrons less tightly, so using the formula the Ep for HCl4 would be larger (more negative) than the Ep for CH4, meaning the interactions in CCl4 are stronger and harder to break. This is why it has a higher boiling point; because it takes more energy to get rid of the stronger attraction.

Pranav Daggubati 3C
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Re: Lecture Question CH4 and CCl4

Postby Pranav Daggubati 3C » Wed Nov 11, 2020 2:10 pm

I'm not sure, I just thought that it was the difference in mass that accounted for this large difference in boiling point

Kayla Law 2D
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Re: Lecture Question CH4 and CCl4

Postby Kayla Law 2D » Wed Nov 11, 2020 2:15 pm

I think your reasoning is correct! I would refer to it not as the interactions in CCl4, but as the interactions between different CCl4 molecules since induced dipole-induced dipole interactions are between molecules and do not refer the bonds in a molecule itself. But other than that I totally agree with your reasoning! :)

Jordi M 2I
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Re: Lecture Question CH4 and CCl4

Postby Jordi M 2I » Wed Nov 11, 2020 2:15 pm

emilyyribarren1k wrote:In Lavelle's slides from today's lecture it says methane (CH4) has a boiling point of -161 degrees celsius and tetrachloromethane (CCl4) has a boiling point of +77 degrees celsius, which is obviously much higher. I just want to double check that the reasoning I came up with for this difference is correct.

Cl is more polarizable than H because it is a larger atom and holds onto its electrons less tightly, so using the formula the Ep for HCl4 would be larger (more negative) than the Ep for CH4, meaning the interactions in CCl4 are stronger and harder to break. This is why it has a higher boiling point; because it takes more energy to get rid of the stronger attraction.

Yes I believe you are correct in your reasoning

emilyyribarren1k
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Joined: Wed Sep 30, 2020 10:10 pm
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Re: Lecture Question CH4 and CCl4

Postby emilyyribarren1k » Wed Nov 11, 2020 2:29 pm

Kayla Law 3G wrote:I think your reasoning is correct! I would refer to it not as the interactions in CCl4, but as the interactions between different CCl4 molecules since induced dipole-induced dipole interactions are between molecules and do not refer the bonds in a molecule itself. But other than that I totally agree with your reasoning! :)

Thank you! I was kind of confused about that as well but that makes sense!


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