12.1. Nitrogen and sulfur
A subsection of Chemistry, 9701, through 12. Nitrogen and sulfur
Listing 10 of 350 questions
Nitrogen makes up about 79% of the Earth’s atmosphere. As a constituent element of proteins, it is present in living organisms. Atmospheric nitrogen is used in the Haber process for the manufacture of ammonia. Write an equation for the formation of ammonia in the Haber process. The Haber process is usually carried out at a high pressure of between 60 and 200 atmospheres (between 60 × 105 Pa and 200 × 105 Pa). State two further important operating conditions that are used in the Haber process. For each of your conditions, explain why it is used. condition 1 reason condition 2 reason State one large-scale use for ammonia, other than in the production of nitrogenous fertilisers. The uncontrolled use of nitrogenous fertilisers can cause environmental damage to lakes and streams. This is known as ‘eutrophication’. What are the processes that occur when excessive amounts of nitrogenous fertilisers get into lakes and streams? In many countries, new cars have to comply with regulations which are intended to reduce the pollutants coming from their internal combustion engines. Two pollutants that may be formed in an internal combustion engine are carbon monoxide, CO, and nitrogen monoxide, NO. Outline how each of these pollutants may be formed in an internal combustion engine. CO NO State the main hazard associated with each of these pollutants. CO NO Pollutants such as CO and NO are removed from the exhaust gases of internal combustion engines by catalytic converters which are placed in the exhaust system of a car. What metal is most commonly used as the catalyst in a catalytic converter? Construct one balanced equation for the reaction in which both CO and NO are removed from the exhaust gases by a catalytic converter.
9701_w10_qp_22
THEORY
2010
Paper 2, Variant 2
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Sulfur and its compounds are found in volcanoes, in organic matter and in minerals. Sulfuric acid, an important industrial chemical, is manufactured from sulfur by the Contact process. The Contact process may be considered to be a three-stage process in which sulfur is converted into sulfuric acid. Each stage consists of a single chemical reaction. Write a balanced equation for each of these reactions in the correct sequence. Where appropriate, use to indicate that the reaction is an equilibrium. first reaction second reaction third reaction Give three different operating conditions that are used in the second stage. condition 1 condition 2 condition 3 State one large scale use of sulfuric acid. Most of the sulfur that is used in the Contact process is recovered from sulfur compounds present in crude oil and natural gas by using the Claus process. In this process, about one third of the hydrogen sulfide, H2S, present in the oil or gas, is converted into sulfur dioxide, SO2. Balance the equation for this reaction. H2S + O2 SO2 + H2O The SO2 formed is then reacted catalytically with the remaining H2S, producing sulfur and water. 2H2S + SO2 3S + 2H2O What are the oxidation numbers of each of the sulfur-containing substances in this reaction? H2S SO2 S Which substance is reduced? Explain your answer. substance explanation The sulfur present in crude oil is removed in order to prevent the formation of sulfur dioxide when fuels such as petrol or diesel fuel are burned in internal combustion engines. Other substances that may be present in the exhaust gases of motor vehicles include CO, CO2, NO/NO2, and unburnt hydrocarbons. The emission of sulfur dioxide can produce ‘acid rain’. Outline, with the aid of equations, how acid rain is formed from the exhaust gases of motor vehicles. State one environmental effect of acid rain. Sulfur dioxide is used to preserve dried fruits and vegetables. What chemical property of SO2 enables it to be used as a food preservative?
9701_w10_qp_23
THEORY
2010
Paper 2, Variant 3
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Write the equation for a reaction in which ethylamine, C2H5NH2, acts as a Brønsted-Lowry base. Ammonia, ethylamine and phenylamine, C6H5NH2, are three nitrogen-containing bases. Place these three compounds in order of basicity, with the most basic first. most basic least basic Explain why you have placed the three compounds in this order. Write an equation for a reaction in which phenol, C6H5OH, acts as a Brønsted-Lowry acid. The pKa values for phenol, 4-nitrophenol and the phenylammonium ion are given in the table. compound pKa OH 10.0 OH O2N 7.2 NH3 + 4.6 Suggest an explanation for the difference in the pKa values of phenol and nitrophenol. Using the information in the table opposite, predict which of the following pKa values is the most likely for the 4-nitrophenylammonium ion. NH3 O2N + Place a tick (✓) in the box beside the value you have chosen. pKa 1.0 4.5 7.0 10.0 Explain your answer to part . Phenylamine can be converted to 4-nitrophenol by the following steps. B OH step 2 step 1 OH NO2 step 3 NH2 Suggest the identity of intermediate B by drawing its structure in the box above. Suggest reagents and conditions for the three steps in the above scheme. reagentconditions step 1 step 2 step 3
9701_w11_qp_41
THEORY
2011
Paper 4, Variant 1
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Write the equation for a reaction in which ethylamine, C2H5NH2, acts as a Brønsted-Lowry base. Ammonia, ethylamine and phenylamine, C6H5NH2, are three nitrogen-containing bases. Place these three compounds in order of basicity, with the most basic first. most basic least basic Explain why you have placed the three compounds in this order. Write an equation for a reaction in which phenol, C6H5OH, acts as a Brønsted-Lowry acid. The pKa values for phenol, 4-nitrophenol and the phenylammonium ion are given in the table. compound pKa OH 10.0 OH O2N 7.2 NH3 + 4.6 Suggest an explanation for the difference in the pKa values of phenol and nitrophenol. Using the information in the table opposite, predict which of the following pKa values is the most likely for the 4-nitrophenylammonium ion. NH3 O2N + Place a tick (✓) in the box beside the value you have chosen. pKa 1.0 4.5 7.0 10.0 Explain your answer to part . Phenylamine can be converted to 4-nitrophenol by the following steps. B OH step 2 step 1 OH NO2 step 3 NH2 Suggest the identity of intermediate B by drawing its structure in the box above. Suggest reagents and conditions for the three steps in the above scheme. reagentconditions step 1 step 2 step 3
9701_w11_qp_42
THEORY
2011
Paper 4, Variant 2
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Questions Discovered
350