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12. Nitrogen and sulfur
A section of Chemistry, 9701
Listing 10 of 350 questions
Nitrogen, N2, is generally an unreactive molecule but it does react under certain conditions. Give two reasons to explain the lack of reactivity of nitrogen. N2 can react with oxygen in an internal combustion engine to form a mixture of NO and NO2. shows a reaction scheme involving N2. reaction 1 reaction 2 reaction 3 N2 NO and NO2 products peroxyacetyl nitrate (PAN) O2 H2O unburned hydrocarbons NO2 NO2 Write an equation to show the formation of a mixture of NO and NO2 in reaction 1. Give the formulae of the products of reaction 2. State one environmental consequence of reaction 3. 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+ 3H22NH3ΔH = –92 kJ mol–1 Use the information in to complete Table 3.1. Table 3.1 compound enthalpy change of formation, ΔHf / kJ mol–1 N2 H2 NH3 Explain how the presence of a catalyst affects the reaction. State and explain the effect, if any, on the rate of the Haber process as the pressure is lowered. The N2F2 molecule has a double covalent bond between its nitrogen atoms. This consists of a σ and a π bond. Complete to show the dot-and-cross diagram for N2F2. Show outer electrons only. F N N F Deduce the hybridisation of the N atoms in N2F2. Draw a diagram of the π bond between the N atoms in N2F2 and describe how it forms.
9701_m24_qp_22
THEORY
2024
Paper 2, Variant 2
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Sulphur and its compounds are found in volcanoes, in organic matter and in minerals. Sulphuric acid, an important industrial chemical, is manufactured from sulphur by the Contact process. There are three consecutive reactions in the Contact process which are essential. Write a balanced equation (using where appropriate) for each of these reactions in the correct sequence. What catalyst is used? Hydrogen sulphide, H2S, is a foul-smelling compound found in the gases from volcanoes. Hydrogen sulphide is covalent, melting at –85 °C and boiling at –60 °C. Draw a ‘dot-and-cross’ diagram to show the structure of the H2S molecule. Predict the shape of the H2S molecule. Oxygen and sulphur are both in Group VI of the Periodic Table. Suggest why the melting and boiling points of water, H2O, are much higher than those of H2S. Hydrogen sulphide burns with a blue flame in an excess of oxygen to form sulphur dioxide and water. Write a balanced equation for the complete combustion of H2S. What is the change in the oxidation number of sulphur in this reaction? from to What volume of oxygen, measured at room temperature and pressure, is required for the complete combustion of 8.65 g of H2S? Give your answer to two decimal places. Hydrogen sulphide is a weak diprotic acid. Its solution in water contains HS– and a few S2– ions. What is meant by the term weak acid? Write an equation, with state symbols, for the first ionisation of H2S when it dissolves in water.
9701_s05_qp_2
THEORY
2005
Paper 2, Variant 0
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Questions Discovered
350