Ammonia latent heat of vaporization is 1369 KJ/kg and water is 2256 KJ/kg
what will latent heat of vaporization be when you mix both at 18% ammonia concentration (Boiling point should be ~57C at this concentration)
I. While considering Hess's law, we get the same final thermodynamic state, H2O(g) and NH3(g), by either considering the vaporization from pure H2O(l) and NH3(l), or by the whole vaporization of aq. ammonia. So, we can calculate the enthalpy of vaporization of both the solution components from aq. ammonia after that of the pure compounds, their specific heats, the specific heat of the ammonia sol., and the enthalpy of sol. of ammonia in water. The last can be found at (e.g.):
Article The enthalpy of solution of ammonia in water and in aqueous ...
Article The enthalpies of solution and formation of ammonia
The specific heat of ammonia aq. sol. can be found (e.g.) at Table 2-202, in: R.H. Perry, D.W. Green, J.O. Maloney (Eds.), "Perry's Chemical Engineers’ Handbook", 7th ed., McGraw-Hill, 1997.
The thermodynamic properties of saturated ammonia can be found at (e.g.) Table 2-232, ibidem.
II. You may alternatively refer to the enthalpy vs. concentration diagram for aq. solutions of ammonia. Cf. (e.g.) Fig. 2.7, ibidem.
III. Partial pressures of either H2O and NH3 over ammonia aq. sol. can be retrieved from (e.g.) Tables 2-21 and 2.23 (respectively), ibidem. The total partial pressure is found (e.g.) at Table 2.24, ibidem.
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