1 Dynamic equilibrium and factors affecting equilibrium

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Oxford Textbook Pages : 106 - 110, 119 - 121

CGP Revision Guide Pages : 47 - 48

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Show Specification Ref : 3.1.6.1

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Question 1 / 5

January 2012 QP – Unit 2 AQA Chemistry A-level_question_2 do not write outside the box ammonia is manufactured by the haber process in which the following equilibrium is established a give two features of a reaction at equilibrium n g h g nh g feature feature marks b explain why a catalyst has no effect on the position of an equilibrium marks extra space question continues on the next page turn over wmp jan chem do not write outside the box c the diagram shows how the equilibrium yield of ammonia varies with changes in pressure and temperature equilibrium yield of ammonia k k k pressure mpa c i use the diagram to state the effect of an increase in pressure at constant temperature on the yield of ammonia use le chatelier s principle to explain this effect effect on yield explanation marks extra space wmp jan chem do not write outside the box c ii use the diagram to state the effect of an increase in temperature at constant pressure on the yield of ammonia use le chatelier s principle to explain this effect effect on yield explanation marks extra space d at equilibrium with a pressure of mpa and a temperature of k the yield of ammonia is d i state why industry uses a temperature higher than k mark d ii state why industry uses a pressure lower than mpa do not include references to safety mark turn over wmp jan chem
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Question 2 / 5

June 2011 QP – Unit 2 AQA Chemistry A-level_question_5 do not write outside the box a sample of nitrogen dioxide gas no was prepared by the reaction of copper with concentrated nitric acid a i balance the equation for the reaction of copper with concentrated nitric acid cu hno cu no no h o a ii give the oxidation state of nitrogen in each of the following compounds hno no mark marks a iii deduce the half equation for the conversion of hno into no in this reaction mark b the following equilibrium is established between colourless dinitrogen tetraoxide gas n o and dark brown nitrogen dioxide gas n o g no g h kj mol b i give two features of a reaction at equilibrium feature feature marks wmp jun chem b ii use le chatelier s principle to explain why the mixture of gases becomes darker in colour when the mixture is heated at constant pressure do not write outside the box marks b iii use le chatelier s principle to explain why the amount of no decreases when the pressure is increased at constant temperature marks turn over for the next question turn over wmp jun chem
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Question 3 / 5

June 2012 QP – Unit 2 AQA Chemistry A-level_question_2 do not write outside the box methanol ch oh is an important fuel that can be synthesised from carbon dioxide a the table shows some standard enthalpies of formation co g h g ch oh g h o g hf kj mol a i use these standard enthalpies of formation to calculate a value for the standard enthalpy change of this synthesis co g h g ch oh g h o g marks extra space a ii state why the standard enthalpy of formation for hydrogen gas is zero mark wmp jun chem b state and explain what happens to the yield of methanol when the total pressure is increased in this synthesis do not write outside the box co g h g ch oh g h o g effect on yield explanation marks extra space c the hydrogen required for this synthesis is formed from methane and steam in a reversible reaction the equation for this reaction is shown below ch g h o g co g h g h kj mol state and explain what happens to the yield of hydrogen in this reaction when the temperature is increased effect on yield explanation marks extra space question continues on the next page turn over wmp jun chem do not write outside the box d the methanol produced by this synthesis has been described as a carbon neutral fuel d i state the meaning of the term carbon neutral mark extra space d ii write an equation for the complete combustion of methanol mark d iii the equation for the synthesis of methanol is shown below co g h g ch oh g h o g use this equation and your answer to part d ii to deduce an equation to represent the overall chemical change that occurs when methanol behaves as a carbon neutral fuel equation mark wmp jun chem do not write outside the box e a student carried out an experiment to determine the enthalpy change when a sample of methanol was burned the student found that the temperature of g of water increased by oc when mol of methanol was burned in air and the heat produced was used to warm the water use the student s results to calculate a value in kj mol for the enthalpy change when one mole of methanol was burned the specific heat capacity of water is j k g marks extra space turn over for the next question turn over wmp jun chem
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Question 4 / 5

June 2013 QP – Unit 2 AQA Chemistry A-level_question_1 section a answer all questions in the spaces provided do not write outside the box sulfuric acid is manufactured by the contact process a in this process sulfur dioxide reacts with oxygen the equation for the equilibrium that is established is so g o g so g h kj mol a i state and explain the effect of a decrease in temperature on the equilibrium yield of so effect of a decrease in temperature on yield explanation marks extra space a ii give two features of a reaction at equilibrium feature feature marks question continues on the next page turn over wmp jun chem b write an equation for the reaction of concentrated sulfuric acid with potassium bromide to form potassium hydrogensulfate and hydrogen bromide do not write outside the box mark c bromine is one of the products formed when concentrated sulfuric acid reacts with hydrogen bromide write an equation for this reaction state the role of sulfuric acid in this reaction equation role of sulfuric acid marks d concentrated sulfuric acid is used in a two stage process to convert methylpropene into methylpropan ol stage ch c ch h so ch c oso oh ch stage ch c oso oh ch h o ch c oh ch h so d i name and outline a mechanism for stage of this conversion name of mechanism mechanism marks wmp jun chem d ii deduce the type of reaction in stage of this conversion mark d iii state the overall role of sulfuric acid in this conversion mark do not write outside the box turn over for the next question turn over wmp jun chem
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Question 5 / 5

June 2014 QP – Unit 4 AQA Chemistry A-level_question_1 section a answer all questions in the spaces provided do not write outside the box this question is about the gaseous equilibrium between compounds e f and g as shown in the equation e g f g g g h kj mol a a mol sample of e was heated in a sealed container with a mol sample of f equilibrium was established at a given temperature and the equilibrium mixture formed contained mol of g calculate the amount in moles of e and of f in this equilibrium mixture marks moles of e moles of f b write an expression for the equilibrium constant kc for this equilibrium state the units of kc marks expression units wmp jun chem do not write outside the box c a different mixture of e and f reached equilibrium at temperature t in a container of volume dm this equilibrium mixture contained mol of e mol of f and mol of g calculate a value of kc for the equilibrium at temperature t marks d the mixture in question c was allowed to reach equilibrium at temperature t in a different container of volume dm state whether the amount of g in the equilibrium mixture will increase decrease or stay the same explain your answer marks effect on the amount of g explanation e the mixture in question c was allowed to reach equilibrium at temperature t in the original container of volume dm the value of kc for the equilibrium was found to have increased state and explain which of t or t is the higher temperature marks higher temperature explanation turn over wmp jun chem
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