1 Le Chatelier’s principle

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Oxford Textbook Pages : 154 - 158

CGP Revision Guide Pages : 80 - 81

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Show Specification Ref : 3.2.3a, 3.2.3b, 3.2.3c, 3.2.3d

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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 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 4 / 5

June 2015 QP – Unit 2 AQA Chemistry A-level_question_4 do not write outside the box a hydrogen is produced in industry from methane and steam in a two stage process in the first stage carbon monoxide and hydrogen are formed the equation for this reaction is ch g h o g co g h g h kj mol a i use le chatelier s principle to state whether a high or low temperature should be used to obtain the highest possible equilibrium yield of hydrogen from this first stage explain your answer marks temperature explanation a ii le chatelier s principle suggests that a high pressure will produce a low yield of hydrogen in this first stage explain in terms of the behaviour of particles why a high operating pressure is used in industry marks wmp jun chem a iii a nickel catalyst is used in the first stage do not write outside the box explain why the catalyst is more effective when coated onto an unreactive honeycomb marks b the second stage is carried out in a separate reactor carbon monoxide is converted into carbon dioxide and more hydrogen is formed the equation for this reaction is co g h o g co g h g h kj mol use le chatelier s principle to state the effect if any of a decrease in the total pressure on the yield of hydrogen in this second stage explain your answer marks effect explanation turn over for the next question turn over wmp jun chem
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Question 5 / 5

June 2011 QP – Unit 4 AQA Chemistry A-level_question_3 do not write outside the box the following dynamic equilibrium was established at temperature t in a closed container p g q g r g h kj mol the value of kc for the reaction was mol dm when the equilibrium mixture contained mol of p and mol of r a give the meaning of the term dynamic equilibrium marks extra space b write an expression for kc for this reaction mark c the volume of the container was dm calculate the concentration in mol dm of q in the equilibrium mixture marks extra space wmp jun chem do not write outside the box d state the effect if any on the equilibrium amount of p of increasing the temperature all other factors are unchanged mark e state the effect if any on the equilibrium amount of p of using a container of larger volume all other factors are unchanged mark f state the effect if any on the value of kc of increasing the temperature all other factors are unchanged mark g state the effect if any on the value of kc of using a container of larger volume all other factors are unchanged mark h deduce the value of the equilibrium constant at temperature t for the reaction r g p g q g mark turn over for the next question turn over wmp jun chem
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