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Topic: higher boiling point of H2O than HF  (Read 11395 times)

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Offline sapta

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higher boiling point of H2O than HF
« on: August 07, 2005, 05:26:24 AM »
HF forms stronger hydrogen bonds than H2O.Why then has H2O a higher B.P. than HF?

my thinking is that HF can stay in associated form even as a gas.So,maybe less no. of bonds need to be splitted.is this the reason?
« Last Edit: August 07, 2005, 06:21:53 AM by sapta »

Offline sdekivit

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Re:higher boiling point of HF than H2O
« Reply #1 on: August 07, 2005, 06:13:36 AM »
HF forms stronger hydrogen bonds than H2O.Why then has HF a higher B.P. than H2O?

my thinking is that HF can stay in associated form even as a gas.So,maybe less no. of bonds need to be splitted.is this the reason?

You correctly state that HF will give stronger H-bonds. Thus if we have 2H2O connceted with a H-bond and 2HF connected with a H-bond. To dissociate these, for which is the needed energy higher ? (H2O can make multiple H-bonds though)
« Last Edit: August 07, 2005, 06:38:12 AM by sdekivit »

Offline sapta

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Re:higher boiling point of H2O than HF
« Reply #2 on: August 07, 2005, 06:23:48 AM »
i had made a horrible mistake in posting my question.i have corrected it now.

Offline sdekivit

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Re:higher boiling point of H2O than HF
« Reply #3 on: August 07, 2005, 06:37:43 AM »
i had made a horrible mistake in posting my question.i have corrected it now.

because it can make multiple H-bonds ( 3 of H2O to 2 of HF) many low energybonds makes a total of a high energy system.
« Last Edit: August 07, 2005, 06:38:39 AM by sdekivit »

Offline hmx9123

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Re:higher boiling point of H2O than HF
« Reply #4 on: August 08, 2005, 04:26:07 AM »
sdekivit is correct.  Even though a single hydrogen bond in HF is stronger than one in water, water has multiple hydrogen bonds, which, when summed, have a greater intermolecular force than that of HF, as HF can only H-bond to two other molecules and water is H-bound to 4, IIRC.

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