Why does the dissolution of NH4NO3 happen if the ∆H is 28.1?

[ScienceMonkey]

1. Why does the dissolution of NH4NO3 happen if the ∆H is 28.1? I'm supposed to be detailed with an equation, and explaining spontaneity.

Does it happen because of the energy created from protonation?

2. And why is only a strong base able to make H3PO4 act as an acid after the 3rd acid dissociation?

Is it because it is electronically unfavorable?

 

[GCT]

1) at constant temperature and pressure what concept relates to sponaneity (depends on both entropy and enthalpy of process).

2)In terms of a base, how strong is PO4^2- compared to H2PO4^-1? What is the Arrehnius concept of an acid base neutralization in perspective of the conjugate acid/bases?