Chapter 6, Problem 87E

The Ostwald process for the commercial production of nitric acid from ammonia and oxygen involves the following steps:

$\begin{array}{ll}4{\text{NH}}_3\left(g\right)+5{\text{O}}_2\hfill & \to 4\text{NO}\left(g\right)+6{\text{H}}_2\text{O}\left(g\right)\hfill \\ 2\text{NO}\left(g\right)+{\text{O}}_2\left(g\right)\hfill & \to 2{\text{NO}}_2\left(g\right)\hfill \\ 3{\text{NO}}_2\left(g\right)+{\text{H}}_2\text{O}\left(l\right)\hfill & \to 2{\text{HNO}}_3\left(aq\right)+\text{NO}\left(g\right)\hfill \end{array}$

a. Use the values of $\Delta H_{\text{f}}^{°}$ in Appendix 4 to calculate the value of ∆Hº for each of the preceding reactions.

b. Write the overall equation for the production of nitric acid by the Ostwald process by combining the preceding equations. (Water is also a product.) Is the overall reaction exothermic or endothermic?