October 17, 2021, 08:48:29 PM
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Topic: NEED ADVISE! Controlled and repeatable exothermic reaction  (Read 165 times)

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Offline JohnnySwede

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NEED ADVISE! Controlled and repeatable exothermic reaction
« on: October 06, 2021, 05:05:48 AM »
Dear all!

Greetings from Sweden!

I am a super amateur when it comes to chemistry, so please forgive me from the start if this is a truly dumb question or if I'm not formulating the question in a correct way... Anyhow, I'll give it a try since this seems like a both good and nice forum, so here we go:

When you create classic "hot ice" by using a supersaturated solution of sodium acetate C2H3NaO2, the exothermic reaction generates heat at 57 degrees Celsius. Right so far? This process is used for i.e. hand warmers and similar products. This process is, apart from generating heat, non-toxic and repeatable (reheat the crystallized solution and it becomes liquid again and can be re-used). Also right? Now to my question: is there any SIMILAR way to achieve exactly the same but with just a SLIGHTLY higher temperature in the exothermic reaction? Meaning: a process that's non-toxic, repeatable and generating just a little more heat, say 10-20 additional degrees Celsius arriving at 70-70 degrees C or so?

I hope there are some good chemists out there who could enlighten me and assist me in this matter!

Offline Borek

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Re: NEED ADVISE! Controlled and repeatable exothermic reaction
« Reply #1 on: October 06, 2021, 10:30:21 AM »
the exothermic reaction generates heat at 57 degrees Celsius. Right so far?

Nope, already wrong :(

Sounds like you are mistaking heat and temperature. Reaction generates heat. Heat heats up the reaction mixture. Final temperature of the mixture can be rather easily calculated from the heat balance equation (assuming you check tables for the molar enthalpy of the reaction).

It happens that in the conditions this reaction runs in (amount of the salt, amount of water) amount of produced heat doesn't warm the mixture beyond some temperature, but that's a very different thing from "generating heat at XX°C".
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Offline JohnnySwede

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Re: NEED ADVISE! Controlled and repeatable exothermic reaction
« Reply #2 on: October 07, 2021, 07:45:58 AM »
Hi,

Thanks for the feedback and sorry for mixing things up - I'm mot very knowledgable in this field. But was the question I'm after clear at least and could you give any concrete advise as to alternatives I could check?

Basically: a supersaturated solution of water and sodium acetate crystallizes at 57 degrees C (the crystallization is exothermic). An example of how this is used for a practical purpose is a hand warmer. The process is repeatable and non-toxic. Now: is there any other kind of superaturated solution where you can achieve the same but at a temp of 70-80 degrees C (and is also be repeatable and non-harmful for humans)?

Thanks for your advise.

Offline Borek

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Re: NEED ADVISE! Controlled and repeatable exothermic reaction
« Reply #3 on: October 07, 2021, 01:55:37 PM »
Now: is there any other kind of superaturated solution where you can achieve the same but at a temp of 70-80 degrees C (and is also be repeatable and non-harmful for humans)?

Never heard about one. Doesn't mean it doesn't exist, although I am a bit sceptic. There are not many substances that will easily create supersaturated solutions, as they are thermodynamically unstable by definition.
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