Neither hydrogen or CO2 is necessarily lost from the system, and hydrogen is most certainly not lost as a result of CO2 gassing off.
LIME REACTION
CaCO3 + H2O → Ca+2 + CO3-2 + H2O
[ Soil ] H Ca+2→ [ Soil ]Ca + 2H+H CO3-2 + H+ → HCO3-1
HCO3-1 + H+ →H2O + CO2 (gas) ↑
(Loss of a free Hydrogen from Hydrogen bonding to form a water molecule and Co2 gassing off as a result) That is the whole point of liming. Reduce the Hydrogen.
These are the equilibrium reactions for various types of liming material (Lindsay 1979.
Chemical Equilibria in Soils)
CaCO3 (calcite) + 2 H+ = Ca2+ + CO2(g) + H2O
CaCO3 (aragonite) + 2 H+ = Ca2+ + CO2(g) + H2O
CaMg(CO3)2 (dolomite) + 4 H+ = Ca2+ + Mg2+ + 2 CO2(g) + 2 H2O
CaO (lime) + 2 H+ =Ca2+ + H2O
Ca(OH)2 (portlandite) + 2 H+ =Ca2+ + 2 H2O
Second, you said the hydrogen attaches to the carbonate ion and bubbles off as CO2 .... it does not.
The Calcium will kick off 2 Hydrogen from the exchange sites on the soil colloids. The 2 Hydrogen that have been displaced will lower the surface soil PHw for a few but quickly attach to the carbonate created in the lime reaction and bubble off as CO2. The PH will increase from the loss of Hydrogen.
The above statement is incorrect. Further, the hydrogen is still in the system as water (assuming an equilibrium reaction), it is just no longer actively contributing to soil acidity.
Third, CO2 doesn't necessarily gas off. It can, but there are other possibilities.
Its reversible because its not a true bond or end to our problem of ammonia gas. Ammonia in water is nothing more than ammonia in water. A FREE HYDROGEN is needed to form a bond with NH3. That is why a PH of less than say 7.2 is needed. Plentiful FREE HYDROGEN.
You need to understand the reaction here.
NH4 + OH <-> NH3 + H2O
There is no free hydrogen needed in this reaction. You can try to add in a free hydrogen here, but the equation won't be balanced nor will it be correct. Now if you want to write the equation for the reaction of NH3 and free soil solution hydrogen ions, have at it, but it really has little to do with surface applied fertilizers and potential volatilization losses. The rest of your post is irrelevant to the topic.