(a)[2]
Explain the meaning of the term enthalpy change of formation.
(b)[3]
Using the values in the table, finish the Hess’ cycle and therefore calculate the enthalpy change, $\Delta H_r$, for this reaction. Show your working.
(c)[2]
Explain why nitrogen and oxygen fail to react at normal atmospheric temperatures.
(d)[1]
State one natural route by which nitrogen oxides are produced.
(e(i))[3]
Explain why $\text{NO}_2$ is described as a homogeneous catalyst in the oxidation of atmospheric sulfur dioxide.
(e(ii))[2]
Write equations that show the two reactions taking place when $\text{NO}_2$ acts as a catalyst in the formation of sulfur trioxide from sulfur dioxide.