12. Nitrogen and sulfur
A section of Chemistry, 9701
Listing 10 of 350 questions
When hydrocarbons such as petrol or paraffin wax are burned in an excess of air in a laboratory, carbon dioxide and water are the only products. When petrol is burned in a car engine, nitrogen monoxide, NO, is also formed. Explain how NO is formed in an internal combustion engine but not formed when a small sample of petrol is burnt in an evaporating basin. The engines of modern motor cars have exhaust systems which are fitted with catalytic converters in order to reduce atmospheric pollution from substances such as NO. State three more pollutants, other than CO2 and H2O, that are present in the exhaust gases of a car engine. and and What is the active material present in the catalytic converter? Write one balanced equation to show how NO is removed from the exhaust gases of a car engine by a catalytic converter. NO is also formed when nitrosyl chloride, NOCl, dissociates according to the following equation. 2NOCl 2NO+ Cl2Different amounts of the three gases were placed in a closed container and allowed to come to equilibrium at 230 °C. The experiment was repeated at 465 °C. The equilibrium concentrations of the three gases at each temperature are given in the table below. concentration / mol dm–3 temperature / °C NOCl NO Cl 2 2.33 × 10–3 1.46 × 10–3 1.15 × 10–2 3.68 × 10–4 7.63 × 10–3 2.14 × 10–4 Write the expression for the equilibrium constant, Kc , for this reaction. Give the units. Calculate the value of Kc at each of the temperatures given. 230 °C 465 °C Is the forward reaction endothermic or exothermic? Explain your answer. The temperature of the equilibrium was then altered so that the equilibrium concentrations of NOCl and NO were the same as each other. What will be the effect on the equilibrium concentration of NOCl when the following changes are carried out on this new equilibrium? In each case, explain your answer. The pressure of the system is halved at constant temperature. A mixture of NOCland NOcontaining equal numbers of moles of each gas is introduced into the container at constant temperature.
9701_s08_qp_2
THEORY
2008
Paper 2, Variant 0
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Questions Discovered
350