## Chemistry and Chemical Reactivity (9th Edition)

$+23.06\ kJ/mol$
From the definition of heat capacity: $155.5\ g\times 4.2\ J/g.K \times(18.6-16.2)\ K)=1567.4\ J$ Positive value because it's an endothermic process. Number of moles of $NH_4NO_3$: $5.44\ g\div 80.04\ g/mol=0.0680\ mol$ Enthalpy of dissolution: $+1.567\ kJ/0.0680\ mol=+23.06\ kJ/mol$