June 21, 2021, 02:04:54 AM
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Topic: What is meant by "Heat" in a reaction and how can I find its value?  (Read 305 times)

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Offline Monoamine

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So chemistry is an empirical science, meaning things like temperature can actually be numerically quantified.

But in so many text books reactions are give like this instead :

A + B   some reagent  :rarrow: heat C + D

So what exactly is meant this (i.e. what temerature), and why don't chemists just use that temperature in the equation in the first place?

Is there maybe a textbook one of you knows that includes this information in reactions? (indicating the solvent wouldn't hurt either  ;), although this is sometimes done ).

Offline Borek

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Re: What is meant by "Heat" in a reaction and how can I find its value?
« Reply #1 on: March 15, 2021, 02:48:44 PM »
There is no exact meaning to that, it just means reaction requires an elevated temperature.

Whenever the exact temperature matters (ie when you are given a recipe, not just a hint at conditions), it is listed.
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Offline Corribus

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Re: What is meant by "Heat" in a reaction and how can I find its value?
« Reply #2 on: March 16, 2021, 11:54:24 AM »
Strictly speaking it means very little, because most reactions have an activation energy, so most reactions require some amount of thermal energy to proceed. There are really two possible implications that are relevant: (a) It distinguishes the fact that the reaction as described in the current context is driven by thermal energy as opposed to, for example, light energy; (b) the reaction in its current context is driven by thermal energy and the rate is practically zero at ambient temperature - i.e., a supplemental heat source needs to be supplied in order to observe formation of products over practically relevant timescales.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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