Enthalpy diagram for the dissolution process
The enthalpy diagram showing exothermic solution formation. Notice that Hsolution is lower in energy than the starting solute/solvent enthalpies. An endothermic process, on the other hand, would show Hsolution as positive, and it would be higher in energy than the starting solute/solvent enthalpies.
Source
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"Lattice NRG for thermodynamic rxn."
http://www.4college.co.uk/a/O/energy.php
Salter
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