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Topic: Why Dichloromethane more dense than water?  (Read 29275 times)

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UOIT

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Why Dichloromethane more dense than water?
« on: October 26, 2007, 03:14:08 PM »
Why does CH2Cl2 solvent (lower layer) have higher density than water while non-chlorinated solvents like hexanes and ether (top layer) have lower density than water, i.e. what exactly is it about Cl that causes this difference?

Offline Yarr

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Re: Why Dichloromethane more dense than water?
« Reply #1 on: October 26, 2007, 03:39:40 PM »
The precise cause is the fact that chlorine is heavier than oxygen, while carbon is lighter.

UOIT

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Re: Why Dichloromethane more dense than water?
« Reply #2 on: October 26, 2007, 05:08:25 PM »
Thank you!!

Offline sjb

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Re: Why Dichloromethane more dense than water?
« Reply #3 on: October 27, 2007, 06:53:13 AM »
The precise cause is the fact that chlorine is heavier than oxygen, while carbon is lighter.

Well, I wouldn't quite go that far, otherwise you run into difficulties explaining why H2S is less dense than H2O (at rtp), even though sulfur is heavier than oxygen...

S

Offline UrbanBlues

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Re: Why Dichloromethane more dense than water?
« Reply #4 on: October 29, 2007, 02:13:38 PM »
Well, Sulfur is less electronegative (2.4) than Oxygen (3.5). Hydrogen-Sulfur bonds are less polar, hence molecules are less attracted by the other molecules. So, as the 'packing' is reduced, the density is a little bit lower ... Hydrogen bonds have a tremendous impact on property, as the boiling point of H20 (100 °C) compared to the point of H2S (-60 °C)

Offline Yarr

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Re: Why Dichloromethane more dense than water?
« Reply #5 on: November 01, 2007, 05:59:23 PM »
Quote from: Sjb
otherwise you run into difficulties explaining why H2S is less dense than H2O

Well that's simple: hydrogen sulphide is a gas, while water is a liquid.

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