Thermodynamics/-80.8 KJ/mol

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Question
If the enthalpy change of NH3 + H2O --> NH4OH is -80.8 KJ/mol does that mean if I add heat +80.8 KJ/mol to NH4OH I wuld get NH3 + H20 I am trying to find out how much energy I need to separate a given amount of ammonium hydroxide.

Answer
Hi Emmanuel,

The answer is yes but it is not that simple. Amonium hydroxide is always giving off NH3, like all things it has a vapour pressure. The heat needed to do this is taken from the surroundings.
And when you have evolved a mole of NH3 it will have absorbed 80.8 KJ from the surroundings. As with all vapour pressures if you raise the temperature it will evolve NH3 faster.

I hope this helps.
Best wishes.
Kevin

Thermodynamics

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Kevin

Expertise

Thermodynamics, chemistry, chemical reactions, kinetics, chemical reaction safety, dust explosion technology, static electricity. General science.

Experience

Over 40 years experience as a practicing thermochemist in industry. Head of the fire and explosion laboratory of a major European chemical company (Ciba-Geigy). Now retired.

Organizations
Institute of Chemical Engineers. Royal Society of Chemistry.

Education/Credentials
Chartered Chemist, Member of the Royal Society of Chemistry (C.Chem MRSC). Msc Sheffield.

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