This may seem like a basic question to educated chemists, but I failed to get this answer on Internet searches. I keep getting more complicated stuff like the Haber process which is not relevant.

At this website it describes how the absorption cooling process works in a propane powered refrigerator. The system uses ammonia, water, and hydrogen in closed loop system. In the evaporator section, it says liquid ammonia reacts with hydrogen gas thus vaporizing it and this process of ammonia boiling in hydrogen absorbs heat from the fridge box. It doesn't mention what the end products of the ammonia and hydrogen reaction are.

Is there a chemical reaction between hydrogen and ammonia here? Or is there no actual chemical reaction, just partial pressure vaporization of ammonia liquid in hydrogen gas?

  • $\begingroup$ No chemical reaction, just vaporization :) $\endgroup$
    – airhuff
    Jun 13, 2017 at 16:56
  • $\begingroup$ Hydrogen then does not undergo a chemical reaction with ammonia but the interaction is physical. It would be interesting to know how the molecules do interact since hydrogen in non-polar while ammonia forms strong dipole-dipole (and H bonds). More clarification on what’s happening here would be helpful! $\endgroup$
    – Mocalue
    Nov 2, 2022 at 2:03

3 Answers 3


No, it does not. I do not know what they described but I am pretty sure liq. ammonia does not react with hydrogen gas. I believe they use hydrogen gas as a carrier but I found that to be questionable as well, since hydrogen in residential setting can be pretty dangerous.


Hydrogen absolutely does react and causes the partial pressure of ammonia to lower dramatically, causing the ammonia to evaporate and absorb great quantities of heat for the operation of the refrigerator. It does not involve strong compound forming bonds (which is the main focus of chemistry students) but weak bonds like Van der Waal forces, acting as a catalyst.


Van der Waal force is Temporary Dipole Induced Dipole interaction, not reaction. The weak association causes absorption of heat.

  • 2
    $\begingroup$ That is London force. Van der Waals force is the superset to that, including also Debye force for permanent-induced dipoles and Keesom force for permanent-permanent dipoles. $\endgroup$
    – Poutnik
    Aug 31, 2022 at 8:00

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