Chapter 9, Problem 9.143CP

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

${\text{3NO}}_{\text{2}}\text{(g)}+{\text{H}}_{\text{2}}\text{O(l)}\to {\text{2HNO}}_{\text{3}}\text{(aq)}+\text{NO(g)}$

$\Delta H°$ = -137.3 kJ

$\text{2NO}(g)+{\text{O}}_{\text{2}}(g)\to 2N{O}_2(g)$

$\Delta H°$ = -116.2 kJ

${\text{4NH}}_{\text{3}}\text{(g)}+{\text{5O}}_{\text{2}}(g)\to \text{4NO(g)}+{\text{6H}}_{\text{2}}\text{O(l)}$

$\Delta H°$= 1165.2 kJ

NH₃(g) $\Delta H°$_f= -46.1 kJ/mol

H₂O(l) $\Delta H°$_f = -285.8 kJ/mol