Varmint
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Anyone know of a heat capacity chart...
For the endothermic/exothermic reaction of common salts when mixed with <del>DHOH</del> [H<sub>2</sub>O]?
I was quite surprized how cold my flask got while working up to a saturated solution of <del>KCL</del> [KCl], the flask got a virtually
instant coating of "dew" (condensed atmospheric <del>HOH</del> [H<sub>2</sub>O]) as soon as I started adding powdered
<del>KCL</del> [KCl].
Not that I have a specific purpose for the data in mind at present, but being the curious type I like to collect information as a normal matter of
course.
you can get the general idea, what if I need to cool a reaction and I've run out of ice, it would be great to know I could just add x amount of salt x
and keep heat in a certain range. Same goes for <del>exothermics</del> [exotherms], knowing how much heat I could generate might just
come in handy at some point in time.
I've tried several searches with various wordings, all I've found is essentially yes, <del>end/exothermics</del> [endotherms/exotherms]
happen with salts, but nothing quantitative.
Even better would be to learn how to derive the data mathematically by way of a deep understanding of the chemisty of <del>eno/exo</del>
[endotherms/exotherms], but that's probably a pipe dream.
Last resort, get an accurate thermo[meter] (digital or glass) and create a chart or table empirically.
Thanks,
DAS
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>:
readability]
[Edited on 2.8.13 by bfesser]
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sargent1015
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Well let's start with the structure of your question. For example, what is DHOH? Also, for ease of reading, HOH should probably be listed as the
almighty water. I will also be a stickler on KCL, since this is not a real compound. Try using actually elements when phrasing your
questions, for example, K and Cl.
Now that we are squared away on format, let's dive into your question. You are basically asking fundamental Physical Chemistry questions
(thermodynamics). To fully understand this, you will need some calculus and a good textbook. After which, you will be able to interpret some data,
such as the chart given in this article about the gibbs free energy of hydration:
Thermodynamics of solvation of ions. Part 5.—Gibbs free energy of hydration at 298.15 K
Yizhak Marcus
J. Chem. Soc., Faraday Trans., 1991,87, 2995-2999
DOI: 10.1039/FT9918702995
Welcome to the world of thermodynamics! 
In short, everything dealing with chemistry can be determined mathamatically, it just depends if you are willing to use math to solve it.
Or you could simply do it empirically. Seems pretty easy.
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Varmint
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Thanks Sarge.
I knew there had to be a way, and I'll be OK with the math, if I can't figure it out my daughter is a math teacher... 
<del>So, how does one enter the numeric subscript so I can properly format?</del>
DAS
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answered in another thread]
[Edited on 2.8.13 by bfesser]
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blogfast25
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@Varmint:
The addition of salts with an endothermic heat of dissolution to a reaction mix is far from smart or practical. Apart from serious contamination
issues, there's also the element of time. Reactions that generate a lot of heat often do so quickly, faster than you can moderate with these
endothermic salts.
But wanting to control the temperature evolution of a reaction due to exotherms is a good thing to do.
Roughly a crude estimate can be obtained as follows. Determine ΔHreaction (the Enthalpy of Reaction) of your specific reaction, in kJ/mole (of
reactant).
Determine how many moles you plan to react, say n. n x ΔHreaction = ΔH (the total amount of reaction heat). Assume now (over-simplistically)
that no heat can escape from your reaction vessel (adiabatic reactor). From the mass m and heat capacity Cp of the reaction products) can then be
established that ΔH = m x Cp x ΔT, with ΔT the estimated increase in temperature (before/after reaction). Solve for ΔT.
Whether ΔT will be acceptable or not will depend on many factors. If judged too high various counter-measures, usually some form of cooling or
the manipulation of n, m or both can then be implemented.
[Edited on 2-8-2013 by blogfast25]
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Varmint
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Of course I never meant adding them to the reaction!
I meant as an impromptu addition to an existing cooling bath if anything, you see your ice is gone, you screwed up and didn't have enough on hand,
maybe, just maybe, a quick mix of KCl in the bath water might make the difference between having to crash the reaction in the safety bucket, or if you
are lucky, it might just get you through.
Bad example? Undoubtably. The premise is, you might just be able to put the cooling/heating reaction to good use, either in a pinch or by design.
Only way you could do either is by knowing the dynamics.
DAS
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blogfast25
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@varmint: just look up various 'cold making mixtures'. Most of these aren't really suitable for impromptu preparation though...
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