We all know that water molecules are always breaking and reforming its hydrogen bonds with other water and/or solute molecules. But why in room temperature hydrogen bonds in pure water breaks? The room temperature thermal energy is about 2.5 KJ/mol, whereas hydrogen bond energy is in the range of 6-15 KJ/mol. So it must not only for thermal fluctuations. (please be specific with reference)
Hi Debasish,
Not sure, whether there is a reference explaining exactly the case of water, but think of chemical kinetics: having 6-15 kJ/mol as an activation energy you will come up with quite high reaction rate (perform calculus yourself to understand the concept! =)). How to do that is described in almost any textbook on physical chemistry.
(Shortly a noticed you are likely to misunderstood another thing: in general not a single molecule has exactly the energy defined by the temperature, there is a distribution- see here https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution)
Sincerely
Oleg
A simple answer is that while you (partially) break one, you (partially) form another, hence the actual activation barrier for breaking the bond is lower than the total energy of the bond.
There are of course thousands of papers, to start with I advice:
https://www.nature.com/articles/379055a0.pdf
http://www.pnas.org/content/pnas/102/37/13019.full.pdf
http://science.sciencemag.org/content/311/5762/832
These are the most valuable references for microscopic information about H-bond. In case of the jump-wait model, I have no problem with the waiting i.e., trapping in a cage. That is also a stable equilibrium state of water. In-spite of that water breaks it H-bond then rotate and change its H-bond partner. What forces that water molecule to breaks its bond, where after some time it will reform again?
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