12.1. Nitrogen and sulfur
A subsection of Chemistry, 9701, through 12. Nitrogen and sulfur
Listing 10 of 350 questions
A sample of a fertiliser was known to contain ammonium sulfate, (NH4)2SO4, and sand only. A 2.96 g sample of the solid fertiliser was heated with 40.0 cm3 of NaOH, an excess, and all of the ammonia produced was boiled away. After cooling, the remaining NaOHwas exactly neutralised by 29.5 cm3 of 2.00 mol dm–3 HCl. In a separate experiment, 40.0 cm3 of the original NaOHwas exactly neutralised by 39.2 cm3 of the 2.00 mol dm–3 HCl. Write balanced equations for the following reactions. NaOH with HCl (NH4)2SO4 with NaOH Calculate the amount, in moles, of NaOH present in the 40.0 cm3 of the original NaOHthat was neutralised by 39.2 cm3 of 2.00 mol dm–3 HCl. Calculate the amount, in moles, of NaOH present in the 40.0 cm3 of NaOHthat remained after boiling the (NH4)2SO4. Use your answers to and to calculate the amount, in moles, of NaOH that reacted with the (NH4)2SO4. Use your answers to and to calculate the amount, in moles, of (NH4)2SO4 that reacted with the NaOH. Hence calculate the mass of (NH4)2SO4 that reacted. Use your answer to to calculate the percentage, by mass, of (NH4)2SO4 present in the fertiliser. Write your answer to a suitable number of signifi cant fi gures. 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? Large quantities of ammonia are manufactured by the Haber process. Not all of this ammonia is used to make fertilisers. State one large-scale use for ammonia, other than in the production of nitrogenous fertilisers.
9701_s13_qp_21
THEORY
2013
Paper 2, Variant 1
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Ammonium nitrate fertiliser is manufactured from ammonia. The fi rst reaction in the manufacture of the fertiliser is the catalytic oxidation of ammonia to form nitrogen monoxide, NO. This is carried out at about 1 × 103 kPa (10 atmospheres) pressure and a temperature of 700 to 850 °C. 4NH3+ 5O24NO+ 6H2O∆H = –906 kJ mol–1 Write the expression for the equilibrium constant, Kp, stating the units. Kp = units What will be the effect on the yield of NO of each of the following? In each case, explain your answer. increasing the temperature decreasing the applied pressure The standard enthalpy changes of formation of NH3and H2Oare as follows. NH3, ∆Hf = –46.0 kJ mol–1 H2O, ∆Hf = –242 kJ mol–1 Use these data and the value of given below to calculate the standard enthalpy change of formation of NO. Include a sign in your answer. 4NH3+ 5O24NO+ 6H2O∆H = –906 kJ mol–1
9701_s13_qp_21
THEORY
2013
Paper 2, Variant 1
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Ammonium sulfate is a fertiliser which is manufactured by the reaction between ammonia and sulfuric acid. Ammonia is described as a weak base and sulfuric acid as a strong acid. By using an equation, explain clearly what is meant by the term weak base. Ammonia and sulfuric acid are both manufactured by processes which involve chemical equilibria. Sulfuric acid is produced from sulfur trioxide which is made by the Contact process. State three important operating conditions for the Contact process for the manufacture of sulfur trioxide. For each of your conditions, you should avoid the use of vague phrases such as ‘high temperature’. condition 1 condition 2 condition 3 How is the sulfur trioxide produced converted into sulfuric acid? Chloropropanols such as 1,3-dichloropropan-2-ol (1,3-DCP) are present in some foods. Cl CH2CH(OH)CH2Cl 1,3-DCP What will be produced when 1,3-DCP is reacted separately with the following reagents under suitable conditions? In each case give the structural formula. concentrated sulfuric acid an excess of ammonia Describe as fully as you can what type of reaction occurs with ammonia.
9701_s13_qp_22
THEORY
2013
Paper 2, Variant 2
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Chile saltpetre is a mineral found in Chile and Peru, and which mainly consists of sodium nitrate, NaNO3. The mineral is purifi ed to concentrate the NaNO3 which is used as a fertiliser and in some fi reworks. In order to fi nd the purity of a sample of sodium nitrate, the compound is heated in NaOHwith Devarda's alloy which contains aluminium. This reduces the sodium nitrate to ammonia which is boiled off and then dissolved in acid. 3NaNO3+ 8Al + 5NaOH+ 18H2O→ 3NH3+ 8NaAl (OH)4The ammonia gas produced is dissolved in an excess of H2SO4 of known concentration. 2NH3 + H2SO4 → (NH4)2SO4 The amount of unreacted H2SO4 is then determined by back-titration with NaOH of known concentration. H2SO4 + 2NaOH → Na2SO4 + 2H2O A 1.64 g sample of impure NaNO3 was reacted with an excess of Devarda's alloy. The NH3 produced was dissolved in 25.0 cm3 of 1.00 mol dm–3 H2SO4. When all of the NH3 had dissolved, the resulting solution was titrated with NaOH. For neutralisation, 16.2 cm3 of 2.00 mol dm–3 NaOH were required. Calculate the amount, in moles, of H2SO4 present in the 25.0 cm3 of 1.00 mol dm–3 H2SO4. Calculate the amount, in moles, of NaOH present in 16.2 cm3 of 2.00 mol dm–3 NaOH. Use your answer to to calculate the amount, in moles, of H2SO4 that reacted with 16.2 cm3 of 2.00 mol dm–3 NaOH. Use your answers to and to calculate the amount, in moles, of H2SO4 that reacted with the NH3. Use your answer to to calculate the amount, in moles, of NH3 that reacted with the H2SO4. Use your answer to to calculate the amount, in moles, of NaNO3 that reacted with the Devarda's alloy. Hence calculate the mass of NaNO3 that reacted. Use your answer to to calculate the percentage by mass of NaNO3 present in the impure sample. Write your answer to a suitable number of signifi cant fi gures. The above reaction is an example of a redox reaction. What are the oxidation numbers of nitrogen in NaNO3 and in NH3? NaNO3 NH3
9701_s13_qp_22
THEORY
2013
Paper 2, Variant 2
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Because of the lack of reactivity of the nitrogen molecule, extreme conditions need to be used to synthesise ammonia from nitrogen in the Haber process. Suggest an explanation for the lack of reactivity of the nitrogen molecule, N2. Under conditions of high temperature, nitrogen and oxygen react together to give oxides of nitrogen. Write an equation for a possible reaction between nitrogen and oxygen. State two situations, one natural and one as a result of human activities, in which nitrogen and oxygen react together. What is the main environmental effect of the presence of nitrogen oxides in the atmosphere? Describe and explain how the basicities of ethylamine and phenylamine compare to that of ammonia. Compound X is a useful intermediate in the synthesis of pharmaceuticals. X can be synthesised from chloromethylbenzene according to the following scheme. T W step 1 step 3 step 4 step 5 X CH2Cl step 2 CH2CN CH2CH2NH CH2 CH2CO2H O C What type of reaction is each of the following? step 1 step 2 Suggest reagents and conditions for step 1, step 2. Draw the structures of the intermediates T and W in the boxes above.
9701_s13_qp_41
THEORY
2013
Paper 4, Variant 1
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Because of the lack of reactivity of the nitrogen molecule, extreme conditions need to be used to synthesise ammonia from nitrogen in the Haber process. Suggest an explanation for the lack of reactivity of the nitrogen molecule, N2. Under conditions of high temperature, nitrogen and oxygen react together to give oxides of nitrogen. Write an equation for a possible reaction between nitrogen and oxygen. State two situations, one natural and one as a result of human activities, in which nitrogen and oxygen react together. What is the main environmental effect of the presence of nitrogen oxides in the atmosphere? Describe and explain how the basicities of ethylamine and phenylamine compare to that of ammonia. Compound X is a useful intermediate in the synthesis of pharmaceuticals. X can be synthesised from chloromethylbenzene according to the following scheme. T W step 1 step 3 step 4 step 5 X CH2Cl step 2 CH2CN CH2CH2NH CH2 CH2CO2H O C What type of reaction is each of the following? step 1 step 2 Suggest reagents and conditions for step 1, step 2. Draw the structures of the intermediates T and W in the boxes above.
9701_s13_qp_43
THEORY
2013
Paper 4, Variant 3
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Questions Discovered
350