question about the self-ionization of water

[gre]

Are the random electric field fluctuations that cause water to self-ionize considered zero-point energy? Also, does self-ionization require the same amount of energy that is normally required to convert H2O -----> H3O(+) + OH(-) which is 79.9 kJ / mol (at 25C).

 

Thanks.

[CaptainPanic]

Zero point energy has little nothing to do with this...

 

The water molecules simply attract each other (normally this attraction is called the "hydrogen bond", but you're correct that these are caused by charge differences and can thus be explained as electric fields).

 

So, in short, it is caused by the characteristics of the atoms (oxygen and hydrogen), which determine the characteristics of the molecule. The two bonds between oxygen and hydrogen in water are at an angle of approx. 109 degrees, and because oxygen is very electronegative and hydrogen is not, these two things cause water to be (very) polar. This in turn means that there is a strong attraction between oxygen atoms in one molecule and hydrogen atoms in another water molecule. This attraction sometimes causes the bonds to break.

 

That's the simple version of the explanation.

 

The self ionization takes exactly the same amount of energy... but you don't measure any temperature difference because the equilibrium reaction proceeds at the same rate in both directions (meaning recombination of OH- and H3O+ to 2 H2O is at the same rate as the "self ionization").

 

I believe (not 100% sure though - interesting question) that water doesn't dissociate ("self ionize") when it's ice... and therefore it won't happen also at very very low temperatures.

 

But finally, this zero point energy is often associated with a lot of BS (using more difficult words, wikipedia says the same)... so my advise is that you don't spend too much time on anything related to the zero point energy because you're likely to find BS (a type of manure which originates from cattle).

Edited May 11, 2009 by CaptainPanic
adding more info

[gre]

Zero point energy has little nothing to do with this...

 

The water molecules simply attract each other (normally this attraction is called the "hydrogen bond", but you're correct that these are caused by charge differences and can thus be explained as electric fields).

 

So, in short, it is caused by the characteristics of the atoms (oxygen and hydrogen), which determine the characteristics of the molecule. The two bonds between oxygen and hydrogen in water are at an angle of approx. 109 degrees, and because oxygen is very electronegative and hydrogen is not, these two things cause water to be (very) polar. This in turn means that there is a strong attraction between oxygen atoms in one molecule and hydrogen atoms in another water molecule. This attraction sometimes causes the bonds to break.

 

So where does the energy come from in self-ionization? Wouldn't the water need to be "moving" a little bit for this to occur?

 

 

 

The self ionization takes exactly the same amount of energy... but you don't measure any temperature difference because the equilibrium reaction proceeds at the same rate in both directions (meaning recombination of OH- and H3O+ to 2 H2O is at the same rate as the "self ionization").

 

What would happen in the equilibrium reaction was stopped (and OH- and H3O+ didn't change back to H2O), or the opposite.

 

I believe (not 100% sure though - interesting question) that water doesn't dissociate ("self ionize") when it's ice... and therefore it won't happen also at very very low temperatures.

 

But finally, this zero point energy is often associated with a lot of BS (using more difficult words, wikipedia says the same)... so my advise is that you don't spend too much time on anything related to the zero point energy because you're likely to find BS (a type of manure which originates from cattle).

 

 

Yep, I've noticed, any search on google for "zero point energy" is pretty much pointless.. Then the good information you have to pay for.. Very frustrating!

Edited May 11, 2009 by gre

[CaptainPanic]

So where does the energy come from in self-ionization? Wouldn't the water need to be "moving" a little bit for this to occur?

 

Molecules in liquid water are moving, shaking and turning all the time...

 

What would happen in the equilibrium reaction was stopped (and OH- and H3O+ didn't change back to H2O), or the opposite.

Then you would die instantly... and you, and all the water in the universe would become some kind of salt. But luckily this won't happen until the laws of nature change... so it's pretty pointless to consider.

 

Yep, I've noticed, any search on google for "zero point energy" is pretty much pointless.. Then the good information you have to pay for! Very frustrating!

So what "good info" are you looking for? Wikipedia clearly explains that no functioning applications have ever been built. The fact that good info is so hard to come by might be because it doesn't exist.

Try finding info about warp-drives. Pretty difficult.

[gre]

Molecules in liquid water are moving, shaking and turning all the time...

 

Doesn't this require some form of energy?

 

Then you would die instantly... and you, and all the water in the universe would become some kind of salt. But luckily this won't happen until the laws of nature change... so it's pretty pointless to consider.

How about just in a test tube.. not the entire world.. What would happen? Would the solution reach a certain temperature, then then stop, would the solution would evaporate?

 

 

 

 

So what "good info" are you looking for? Wikipedia clearly explains that no functioning applications have ever been built. The fact that good info is so hard to come by might be because it doesn't exist.

Try finding info about warp-drives. Pretty difficult.

 

 

By good info, I mean all the details, which I'm pretty sure Wiki lacks..

[John Cuthber]

The temperature of an object is a measure of the energy it has on a microscopic scale.

Water (in the liquid state) has enough energy distributed among it's molecules that, from time to time, they get split into ions.

 

Incidentally, there are two things for which the phrase "zero point energy" gets used and they are both irrelevant in this case.

[gre]

The temperature of an object is a measure of the energy it has on a microscopic scale.

Water (in the liquid state) has enough energy distributed among it's molecules that, from time to time, they get split into ions.

 

Ah.. I see. So "random field fluctuations" might as well be considered random temperature fluctuations.

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Consecutive posts merged

So, what is the (microscopic?) "temperature" (from 25C) required between two water molecules to ionize them into H3O+ and OH- ... or am I still lost?

Edited May 11, 2009 by gre
Consecutive posts merged.