Chapter 8, Problem 8.121CHP

Set up a Hess’s law cycle, and use the following information to calculate ΔH°_f for aqueous nitric acid, HNO₃(aq). You will need to use fractional coefficients for some equations.

$\begin{array}{ll}3{\text{NO}}_2(g)+{\text{H}}_2\text{O}(l)\stackrel{}{\to }2{\text{HNO}}_3(aq)+\text{NO}(g)\hfill & \Delta H°=-137.3\text{kJ}\hfill \\ 2\text{NO}(g)+{\text{O}}_2(g)\stackrel{}{\to }2{\text{NO}}_2(g)\hfill & \Delta H°=-116.2\text{kJ}\hfill \\ 4{\text{NH}}_3(g)+5{\text{O}}_2(g)\stackrel{}{\to }4\text{NO}(g)+6{\text{H}}_2\text{O}(l)\hfill & \Delta H°=-1165.2\text{kJ}\hfill \\ {\text{NH}}_3(g)\Delta H{°}_{\text{f}}=-46.1\text{kJ/mol}\hfill & \hfill \\ {\text{H}}_3\text{O}(l)\Delta H{°}_{\text{f}}=-285.8\text{kJ/mol}\hfill & \hfill \end{array}$