1 Rate equations

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Oxford Textbook Pages : 272 - 275, 278 - 280, 282 - 283

CGP Revision Guide Pages : 116, 118, 120 - 121

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Show Specification Ref : 5.1.1a, 5.1.1d, 5.1.1e, 5.1.1f, 5.1.1g

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Question 1 / 5

January 2011 QP – Unit 2 AQA Chemistry A-level_question_9 section b answer all questions in the spaces provided do not write outside the box a student devised an experiment to investigate the enthalpies of combustion of some alcohols the student chose the following series of primary alcohols name formula methanol ethanol propan ol butan ol pentan ol alcohol x heptan ol ch oh ch ch oh ch ch ch oh ch ch ch ch oh ch ch ch ch ch oh ch ch ch ch ch ch oh ch ch ch ch ch ch ch oh a i name alcohol x mark a ii state the general name of the type of series shown by these primary alcohols mark a iii draw the displayed formula of the position isomer of butan ol a iv using o to represent the oxidising agent write an equation for the oxidation of butan ol to form an aldehyde mark mark wmp jan chem a v draw the displayed formula of a functional group isomer of this aldehyde do not write outside the box b the student carried out a laboratory experiment to determine the enthalpy change when a sample of butan ol was burned the student found that the temperature of g of water increased by oc when x mol of pure butan ol was burned in air and the heat produced was used to warm the water mark use the student s results to calculate a value in kj mol for the enthalpy change when one mole of butan ol is burned the specific heat capacity of water is j k g marks extra space question continues on the next page turn over wmp jan chem c i give the meaning of the term standard enthalpy of combustion do not write outside the box marks extra space c ii use the standard enthalpy of formation data from the table and the equation for the combustion of butan ol to calculate a value for the standard enthalpy of combustion of butan ol ch ch ch ch oh i o g co g h o i h f kj mol ch ch ch ch oh i o g co g h o i marks extra space wmp jan chem do not write outside the box d the student repeated the experiment described in part b and obtained an experimental value for the enthalpy of combustion for each alcohol in this series these experimental values were then compared with calculated values from standard enthalpies of formation as shown in the graph below enthalpies of combustion values for a series of primary alcohols enthalpy of enthalpy of combustion combustion kj mol kj mol calculated experimental m of alcohol mr of alcohol d i in terms of bonds broken and bonds formed explain why the calculated values of enthalpies of combustion of these alcohols when plotted against mr follow a straight line marks extra space d ii give two reasons why the experimental values obtained by the student are lower than the calculated values using the enthalpy of formation data marks turn over wmp jan chem
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Question 2 / 5

June 2010 QP – Unit 2 AQA Chemistry A-level_question_8 section b answer all questions in the spaces provided do not write outside the box glucose produced during photosynthesis in green plants is a renewable source from which ethanol can be made ethanol is a liquid fuel used as a substitute for petrol the processes involved can be summarised as follows process photosynthesis in green plants co h o c h o o process fermentation of glucose to form ethanol process complete combustion of ethanol ch ch oh o co h o a state three essential conditions for the fermentation of aqueous glucose in process write an equation for the reaction that takes place during this fermentation marks extra space wmp jun chem do not write outside the box b it has been claimed that there is no net carbon greenhouse gas emission to the atmosphere when ethanol made by process is used as a fuel state the term that is used to describe fuels of this type use the equations for processes and to show why it can be claimed that there is no net emission of carbon containing greenhouse gases marks extra space question continues on the next page turn over wmp jun chem do not write outside the box c use the information from the equation for process on page and the mean bond enthalpies from the table below to calculate a value for the enthalpy change for this process c h c c c o o h c o o o mean bond enthalpy kj mol give one reason why the value calculated from mean bond enthalpies is different from the value given in a data book marks extra space wmp jun chem do not write outside the box d a student carried out a simple laboratory experiment to measure the enthalpy change for process the student showed that the temperature of g of water increased by c when g of pure ethanol was burned in air and the heat produced was used to warm the water use these results to calculate the value in kj mol obtained by the student for this enthalpy change the specific heat capacity of water is j k g give one reason other than heat loss why the value obtained from the student s results is less exothermic than a data book value marks extra space 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_6 do not write outside the box chloromethanes such as dichloromethane and trichloromethane are produced in industry as they have many uses trichloromethane has been used in the manufacture of the refrigerant chlorodifluoromethane a chlorine can react with dichloromethane ch cl to form trichloromethane chcl a i write an equation for each of the following steps in the mechanism for this reaction initiation step first propagation step second propagation step marks a ii give one essential condition for this reaction and name the type of mechanism essential condition type of mechanism marks question continues on the next page turn over wmp jun chem do not write outside the box b an organic product x with mr is obtained when chlorine reacts with trichloromethane b i write an equation for the overall reaction of chlorine with trichloromethane to form x by the same mechanism as that outlined in part a i mark b ii the following infrared spectrum was obtained for a sample of x produced in this reaction transmittance wavenumber cm use this infrared spectrum to explain why it is possible to deduce that this sample of x contains no trichloromethane you may find it helpful to refer to table on the data sheet marks extra space wmp jun chem do not write outside the box c explain with the aid of equations and the intermediates that form in the ozone layer why the european union has banned the use of chlorodifluoromethane chclf as a refrigerant marks extra space d the compound tetrafluoropropene is the refrigerant used in all new car air conditioners d i draw the displayed formula for tetrafluoropropene d ii give one reason why tetrafluoropropene is a more environmentally acceptable refrigerant than chlorodifluoromethane mark mark turn over wmp jun chem
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Question 4 / 5

June 2014 QP – Unit 2 AQA Chemistry A-level_question_9 ethanol is an important fuel do not write outside the box a a dilute aqueous solution of ethanol can be produced by the fermentation of an aqueous solution of glucose it is claimed that the ethanol obtained from this solution is a carbon neutral biofuel write an equation for this fermentation reaction give two other essential conditions for this reaction to produce a good yield of ethanol name a process used to produce a much more concentrated solution of ethanol from a dilute aqueous solution state the meaning of the term carbon neutral in the context of this biofuel marks extra space question continues on the next page turn over wmp jun chem do not write outside the box b a student carried out a laboratory experiment to determine the enthalpy change when a sample of ethanol was burned the heat produced was used to warm some water in a copper calorimeter the student found that the temperature of g of water increased by c when mol of pure ethanol was burned in air use the student s results to calculate a value in kj mol for the enthalpy change when one mole of ethanol is burned the specific heat capacity of water is j k g deduce two reasons why the student s value for the standard enthalpy of combustion of ethanol is different from a data book value of kj mol marks extra space wmp jun chem do not write outside the box c mean bond enthalpies can be used to calculate enthalpies of reaction c i give the meaning of the term mean bond enthalpy marks c ii consider the mean bond enthalpy data in table table c h c c c o o o c o o h mean bond enthalpy kj mol to be calculated use the data in table and the equation shown to calculate a value for the bond enthalpy for the o o double bond in an oxygen molecule marks ch ch oh g o g co g h o g h kj mol end of questions wmp jun chem
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Question 5 / 5

June 2015 QP – Unit 2 AQA Chemistry A-level_question_7 do not write outside the box a propanone can be formed when glucose comes into contact with bacteria in the absence of air a i balance the following equation for this reaction of glucose to form propanone carbon dioxide and water c h o ch coch co h o a ii deduce the role of the bacteria in this reaction mark mark b propanone is also formed by the oxidation of propan ol b i write an equation for this reaction using o to represent the oxidising agent mark b ii state the class of alcohols to which propan ol belongs mark wmp jun chem do not write outside the box c a student determined a value for the enthalpy change when a sample of propanone was burned the heat produced was used to warm some water in a copper calorimeter the student found that the temperature of g of water increased by c when mol of pure propanone was burned in air use the student s results to calculate a value in kj mol for the enthalpy change when one mole of propanone is burned the specific heat capacity of water is j k g marks question continues on the next page turn over wmp jun chem d define the term standard enthalpy of combustion do not write outside the box marks e use the mean bond enthalpy data in table and the equation given below table to calculate a value for the standard enthalpy change when gaseous propanone is burned marks table c h c c c o o h c o o o mean bond enthalpy kj mol ch coch g o g co g h o g wmp jun chem do not write outside the box f suggest two reasons why the value obtained by the student in question c is different from the value calculated in question e marks reason reason turn over for the next question turn over wmp jun chem
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