HCl + Snow = -42f?

[Sedit]

Can any one explain the mechanics behind why HCl dumped into a bucket of snow will quickly reach -42 degrees F yet shaved ice will not get there no matter how hard I try.

 

My general hypothesis has to do with hydrogen bonding, or lack there of anyway, with snow compared to the structure of ice but was woundering if anyone had more insite into this then my self.

 

 

~Sedit

[hermanntrude]

adding acid to water shoudl result in a temperature increase.

[YT2095]

HCl or NaCl?

and I think looking into something Simple like Surface Area would be a better 1`st step.

 

Then you can set about complicating things

[John Cuthber]

adding acid to water shoudl result in a temperature increase.

 

What would your second guess be?

Acids (particularly H2SO4) are used in cooling mixtures just like salt or CaCl2.

IIRC the Merck index lists a few.

 

What I can't explain is why snow works better than shaved ice.

[Sedit]

"adding acid to water shoudl result in a temperature increase."

Nope not even a little bit the temperature will drop from about 28 degrees F to -42 very rapidly and with in 10 seconds or so it will be anyware from -38 to -42

 

"and I think looking into something Simple like Surface Area would be a better 1`st step.

Then you can set about complicating things "

 

Hence the reason for using shaved ice on subsequent experiments only to find that -15 thru -20 was the limits not matter how fine I managed to get it.

 

Complicating things is the level I am at with it at the moment because I want to find how to get it to drop lower using other acids or salts ect...Understanding the mechanism is essential for this. My first instinct has to be that the fact that there is more hydrogen bonding in ice compaired to snow means that energy is being released as these are breaking and forcing it to reach an equilibrium quicker then it will with snow. But as i said these are all just guesses at the moment.

 

Lack of anymore snow has put a damper on experimenting and I want to try to get the shaved ice to get as low as possible also. A block of Ice is easy enough to make but i still havent figured out this weather control problem : ).

 

~Sedit

[insane_alien]

are you talking about hydrochloric acid as a solution or the gas itself (or even the liquified form) ?

 

if the former then the water in the solution starts freezing taking the HCl out of solution resulting in an exothermic process which can cool it down.

 

if the later(using liquid form) its simple because liquid HCl is much colder than the snow.

 

if gaseous HCl then you are lying.

[hermanntrude]

weird thing is that when i add acid to water it gets hot.

---

Merged post follows:

Consecutive posts merged

and seriously, who uses fahrenheit? it's a temperature scale based on the freezing point of salt water and the rectal temperature of a cow.

[insane_alien]

yes, when you add it to liquid water it does because diluting it is exothermic, concentrating it is necessarily endothermic. by freezing the water it is dissolved in(using snow in this case) you are concentrating the acid which is an endothermic process.

[UC]

A list of highly endothermic dissolutions (a little more than halfway down):

 

http://chemieunterricht.de/dc2/tip/08_98.htm

 

From my understanding, Eis is ice (preferably as snow) and kaltwasser is "cold water" (ice cold, I can only imagine). These temperatures are probably only available if you use finely powdered solids and snow and mix the two rapidly.

 

I have 5kg of MgCl2*6H2O that I bought on clearance for $1 at walmart last year. Sadly, it's a little late for snow, but I can try with finely pulverized ice.

[Sedit]

"and seriously, who uses fahrenheit"

Just what my cheep digital thermometer reads thats all. Im sure you have seen them black bulbus top with a metal probe.

 

"if gaseous HCl then you are lying."

No it was 35%(maybe 32% cant remeber) muratic acid from home depot, So your saying that gas dont work? Ok... that was going to be my next experiment when given the chance to gas the snow. Honestly I thought that the lack of H2O in the system was going to give me better results.

Now you also stated that the acid concentrating it self is endothermic. IIRC 45% is whats reached under ice cold conditions for HCl solutions correct? So would bubbling Dry HCl into some 30<>% with snow on top that will melt and concentrat when the gas hits it still produce a null effect or would it behave differntly?

 

 

"yes, when you add it to liquid water it does because diluting it is exothermic, concentrating it is necessarily endothermic. by freezing the water it is dissolved in(using snow in this case) you are concentrating the acid which is an endothermic process.

"

 

Now is this why it cant get as low using the less finly ground shaved ice as opposed to the snow?

 

Because even though surface area looks pretty much the same I would be running into acid dissasociating in water generating heat while the acid attempts to concentrat in an endo thermic process? With snow it would seem that the latur would gain the upper hand leading to the much much lower temperatures..

 

Also insane_alien some one else that I asked about this said that sulfuric has a greater ability to remove energy compared to HCl is this true and would it be worth it to use my (precious for the time being) 95%Sulfuric to perform this next time it snows.

 

 

@UC

Thanks for the link man Havent fully translated it yet because im still typing this while trying to read it but at first glance it is amazing to see that MgCl hydrate can reach such low temperatures. BTW I thought Finely pulverized Ice would work the same also or atlest almost as good hence the reason for starting this threed.. it dont work no ware as near as good and I would think thatas the temperature extreams got as low as -94 it would cause more of a problem..

Also yes I noticed that it has to be added for the HCl any way as fast as possible(also stired into a thin slush). One cant just add a little snow then add a little acid then add a little snow ect... to keep the temp down it has to be done all at once or the temperature rises because of the acid temp I believe.

 

"it's a little late for snow"

Its getting there for here also but we keep getting wet rain and snow which is driving me nuts. Its like a tease.

[hermanntrude]

yes, when you add it to liquid water it does because diluting it is exothermic, concentrating it is necessarily endothermic. by freezing the water it is dissolved in(using snow in this case) you are concentrating the acid which is an endothermic process.

 

my bad... didn't read it very carefully.

[Sedit]

Iv included a rough translation for any one interested in the link to the german artical that UC posted a link for.

 

Prof. Blumes tip of the month August 1998 (tip-No. 14) With Kältemischungen there are also in the summer ice

.

..{Skiping the beging that is just discussing the yearly ice harvest and its uses ect..

}

 

What is physical-chemical behind it?

You combine a salt in liquid water, causing it to the Wasserdipole by the ions of salt wrapping and so the ionic crystal lattice out.

This procedure is usually endothermic, as the new Ion-dipole interaction is smaller than the lattice energy of salt. The heat of a solution for the salt is therefore withdrawn from the surrounding area; solution and vessel cool down from (try 1). With sodium nitrate we reach a temperature of -5,3 °C.

 

You combine with a firm a salt water ice, dissolves the salt to bring even though this is much slower (try 2). Where does the water to solve? You to know that ice melts under pressure, and therefore under influence of air pressure. That is why ice always with a thin layer of water coated. With this liquid water is the ice in a dynamic equilibrium.

 

The water for solving the salt comes from this balance and is constantly being copied. So the equilibrium and ice, slowly disappears. (This effect one uses by the way to provide in Winter ice on footpath and streets to fight.) In this operation comes to solving the salt is still the melting of ice. Whose been together with heat of a solution of salt from the surrounding area taken. This also reduces the temperature of the mix ice/salt characteristics.

 

Recipes for freezing mixture In the literature are very many Mischungsangaben to find. But soft information about the composition and reached temperatures in various tables often widely. In our table will give you some Mischungsbeispiele you can even check. The cheapest is the suitable cooling liquid with salt, at the du -21,3 °C can reach you can (try 3). Instead of mineral salts, you also non-ionic compounds as additions to production of freezing mixture.

------------------------------------------

From here it goes on to the chart to show the temperature that it reaches

Kaltwasser = chilled water possibly salt water?

eis = ice

[CharonY]

Funny, before he retired Prof. Blume's office was about four doors from mine. Fancy reading something from him again. In any case, I suppose despite the babelfishy translation it should be somewhat clear, or does anyone require a more proper translation?

And Kaltwasser just means pre-cooled water. E.g. directly from the fridge (w/o ice).

[Sedit]

Yeh i used a nice little program called babylon which just a click of a mouse on a paragraph and it translates it. I wasnt to sure about the Kaltwasser it said that it ment chilled water but the kalt makes it sound like something was being lost in translation. If you can translate it would be be kind enough to tell me what the picture of the reaction mechanism translates to? my program cant do pictures.

 

thanks in advance

 

~Sedit

[UC]

Yeh i used a nice little program called babylon which just a click of a mouse on a paragraph and it translates it. I wasnt to sure about the Kaltwasser it said that it ment chilled water but the kalt makes it sound like something was being lost in translation. If you can translate it would be be kind enough to tell me what the picture of the reaction mechanism translates to? my program cant do pictures.

 

thanks in advance

 

~Sedit

 

kalt = cold?

 

I snagged the link from an old thread over on sciencemadness.org. I believe some testing was done and better results were when everything had been prechilled as much as possible. My larger freezer at home reaches -20C. A problem though is measuring the temperature you achieve.

Edited February 26, 2009 by UC

[Sedit]

Im having issues reproducing there data using H2SO4 I diluted my 96% H2SO4 down to 60%(maybe the problem I just noticed it says 66%) and added it to finely crushed Ice,

Where as under the same conditions and batch of crushed Ice HCl reached -19.5'-' -20 as a control the H2SO4 only reached about -9.

[CharonY]

If you can translate it would be be kind enough to tell me what the picture of the reaction mechanism translates to?

 

I kind of lost track of this thread, so maybe I am a bit late. It basically only states: Ice (solid)+Energy <--> Water (liq)

The text also mentions that reachable temps vary widely in literature.

 

kalt = cold?

yupp.

[Mr Skeptic]

Freezing point depression is a colligative property, so it depends more on the concentration of your solution than on the solute. Seeing as how HCl has a lower molecular mass than H2SO4, the same mass of HCl would cause a much bigger freezing point depression than the same mass of H2SO4. As to why there should be a difference between snow and shaved ice, I think that the surface area of the snow would be much higher but I don't think that should make a difference other than speed. Alternately, maybe the snow is contaminated (but it would have to be very contaminated to change its freezing point significantly).

 

Also, dissolving an acid in water releases heat, but this heat is absorbed by the melting ice, and the temperature drops as the solution has a lower freezing point.

[Sedit]

Well I have an update to this threed and I have a hunch that -42 was a huge understatment. My thermometer which i didnt take into account at the time is only suppose to go to -40 degrees F and yet I constantly get reading of -42(two differnt snow falls also so unless its the nitrogen in the snow then contamination is pretty much out of the question).

As an attempt at calibration I tryed to liquify NH3 which I know liquifys at -28 degrees C. What I got was a small chunk of ice crystals that I thought ment the NH3 wasnt dry enough but after putting it into a cold water bath it quickly vaporised leaving not a trace of condensation as water in the mix would have done.This means it is quite possible that HCl/snow is reaching temperatures of -78 degrees C and below. I have a full year to get a proper thermometer now and this threed my die for sometime but I will keep you updated because I am very interested in acheiving low temperatures.

 

The HCl I am using is standard over the counter muratic acid 35%.

 

After a few snow falls and many replications I have noticed wet snow can not even compair to dry snow in the least. This may explain why shaved ice isn't working either. Possible if it was shaved then refrozen to get rid of the trace surface liquid water then I may get better results.

 

Also still have yet to achieve there results with sulfuric acid even under proper conditions.