Can Hydrogen be made from air and water?

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Discussion Overview

The discussion centers around the feasibility of producing hydrogen from air and water, specifically through the formation of ammonium nitrate. Participants explore the thermodynamics of the proposed reactions and the stability of water as a source of hydrogen.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant proposes a reaction involving nitrogen and water to produce ammonium nitrate and hydrogen, questioning its exothermic nature.
  • Another participant argues that ammonium nitrate is typically produced through a different chemical process involving nitric acid and ammonium hydroxide.
  • A participant suggests that producing hydrogen sustainably could involve a cycle where hydrogen is converted to water and then back to hydrogen through biological processes.
  • Some participants discuss the stability of water and its bonds, with one mentioning that hydrogen gas can be produced by reacting water with inorganic acids and metals, or through electrolysis.
  • Concerns are raised about the enthalpy of formation of ammonium nitrate and whether the proposed reaction from water and nitrogen is exothermic or endothermic.
  • One participant explains the calculation of reaction enthalpy using Hess's Law and emphasizes the importance of considering activation energy in determining reaction viability.
  • A later reply provides a detailed calculation of the enthalpy changes for the proposed reactions, concluding that producing hydrogen from the second reaction is endothermic and consumes more energy than direct methods.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of producing hydrogen from the proposed reactions, with no consensus reached on the viability of the method involving ammonium nitrate. There are also disagreements regarding the thermodynamic properties of the reactions discussed.

Contextual Notes

There are unresolved questions regarding the assumptions made in the calculations of enthalpy and the specific conditions under which the reactions would occur. The discussion also highlights the complexity of the chemical processes involved.

sr241
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Is forming ammonium nitrate and hydrogen from air and water is possible.

N2+3H2O > NH4NO3 +H2

Is this reaction exothermic?

Ammonium nitrate has enthalpy of formation of -365.1
 
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no, it is not possible, ammonium nitrate is ussually produced mixing nitric acid and ammonium hidroxide,

HNO3+NH4OH--->NH4NO3+H2O

you want to blow something up huh?
 
Actually I was looking for sustainable way to produce hydrogen. Ammonium nitrate is widely used as fertilizer, so there will be a cycle hydrogen to water again to hydrogen. and a nitrogen cycle: nitrogen to ammonium nitrate to nitrogen by plants>animals>secretion>bacteria

Is water is the stablest form of hydrogen?
 
The OH bond is pretty stable, and there is certainly a lot of water on the Earth's surface. I believe M(OH)x, where M is a metal element and x is some integer, are quite stable, but not sure which one is most.
 
also water is very stable because of hydrogen bonds , if you want to produce Hydrogen gas just add an inorganic acid to some metal, like HCl and Al for instance, there are many other ways, like electrolysis on water
 
sr241 said:
Ammonium nitrate has enthalpy of formation of -365.1

where did you come up with that number?
 
i found it from internet (wikipedia)
production of ammonium nitrate from ammonia and nitric acid is exothermic . but my question is it exothermic from water and nitrogen?
 
well, I already got a warning for answering just like that, so why don't you calculate it yourself? just look for an enthalpy table and use Hess's Law, draw some lewis's structures to know which bonds are broken and which are formed
 
No. The enthalpy of formation is a function of state and is calculated as if the compound is formed directly from its constituents. If you know the enthalpy of formation of the reactants (which are also compounds in your case) and of the products, then the enthalpy of the reaction is:

[tex] \Delta_{r} H = \sum{H_{f}(\mathrm{products})} - \sum{H_{f}(\mathrm{reactants})}[/tex]

IF this turns out to be negative, the reaction is exoergic. If it is positive, it is endoergic. However, this does not give you the whole information about the kinetics of the reaction, as there might be a huge potential barrier for this reaction to start (activation energy).
 
  • #10
2 N2(0)+4 H2(0)+3 02(0) > 2 NH4NO3 [(-365.1)*2]
since enthalpy is negative the first reaction is exothermic

N2(0)+3 H2O[(-241.8 )*3] > NH4NO3(-365.1) +H2(0)

so enthalpy of second reaction will be -365.1 - (-241.8 *3)= +360.3, thus the second reaction is endothermic right

values in brackets () are enthalpy of formation.

So producing hydrogen from second reaction is not viable since it consumes more energy 1.7 times more to produce one mole of hydrogen than directly from water, right?
 
Last edited:

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