Nitrogen monoxide is quickly oxidised to nitrogen dioxide. $2\text{NO}(g) + \text{O}_2(g) \rightarrow 2\text{NO}_2(g)$ Nitrogen dioxide may then dimerise to give dinitrogen tetroxide. $2\text{NO}_2(g) \rightarrow \text{N}_2\text{O}_4(g) \quad \Delta H^{\circ} = -58\,\text{kJ mol}^{-1}$ $\Delta H_f^{\circ}(\text{NO}) = +91\,\text{kJ mol}^{-1}$ and $\Delta H_f^{\circ}(\text{NO}_2) = +34\,\text{kJ mol}^{-1}$ What is the value of the standard enthalpy change for the reaction shown? $2\text{NO}(g) + \text{O}_2(g) \rightarrow \text{N}_2\text{O}_4(g)$
- A$+56\,\text{kJ mol}^{-1}$
- B$-1\,\text{kJ mol}^{-1}$
- C$-115\,\text{kJ mol}^{-1}$
- D$-172\,\text{kJ mol}^{-1}$