Nitrogen, N2, is generally an unreactive molecule but it does react under certain conditions.

1. (a)Give two reasons to explain the lack of reactivity of nitrogen.[2]
2. (b)(i)N₂ can react with oxygen in an internal combustion engine to form a mixture of NO and NO2. Fig. 3.1 shows a reaction scheme involving N2. reaction 1 N2 O2 NO and NO2 reaction 2 NO2 H2O products reaction 3 NO2 unburned hydrocarbons peroxyacetyl nitrate (PAN) [Figure 3.1] Write an equation to show the formation of a mixture of NO and NO2 in reaction 1.[1]
3. (b)(ii)Give the formulae of the products of reaction 2.[1]
4. (b)(iii)State one environmental consequence of reaction 3.[1]
5. (c)(i)The Haber process involves the reaction of N2 and H2 to form ammonia, NH3. A catalyst is used, which allows the process to be carried out at a lower temperature and pressure. N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH = −92 kJ mol-1 Use the information in (c) to complete Table 3.1. Table 3.1 compound N2 H2 NH3 enthalpy change of formation, ΔHf / kJ mol-1[2]
6. (c)(ii)Explain how the presence of a catalyst affects the reaction.[1]
7. (c)(iii)State and explain the effect, if any, on the rate of the Haber process as the pressure is lowered.[2]
8. (d)(i)The N2F2 molecule has a double covalent bond between its nitrogen atoms. This consists of a σ and a π bond. Complete Fig. 3.2 to show the dot-and-cross diagram for N2F2. Show outer electrons only. F N N F [Figure 3.2][2]
9. (d)(ii)Deduce the hybridisation of the N atoms in N2F2.[1]
10. (d)(iii)Draw a diagram of the π bond between the N atoms in N2F2 and describe how it forms.[2]

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