AQA Jun 2011 Paper 5 Q5

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do not write outside the box redox reactions occur in the discharge of all electrochemical cells some of these cells are of commercial value the table below shows some redox half equations and standard electrode potentials half equation zn aq e zn s ag o s h aq e o g h aq e f g e ag s h o i h o i f aq e v a in terms of electrons state what happens to a reducing agent in a redox reaction mark b use the table above to identify the strongest reducing agent from the species in the table explain how you deduced your answer strongest reducing agent explanation marks c use data from the table to explain why fluorine reacts with water write an equation for the reaction that occurs explanation equation marks wmp jun chem do not write outside the box d an electrochemical cell can be constructed using a zinc electrode and an electrode in which silver is in contact with silver oxide this cell can be used to power electronic devices d i give the conventional representation for this cell marks d ii calculate the e m f of the cell mark d iii suggest one reason why the cell cannot be electrically recharged mark e the electrode half equations in a lead acid cell are shown in the table below half equation pbo s h aq hso aq e pbso s h o i pbso s h aq e pb s hso aq e v to be calculated e i the pbo pbso electrode is the positive terminal of the cell and the e m f of the cell is v use this information to calculate the missing electrode potential for the half equation shown in the table mark e ii a lead acid cell can be recharged write an equation for the overall reaction that occurs when the cell is being recharged marks question continues on the next page turn over wmp jun chem do not write outside the box f the diagrams below show how the e m f of each of two cells changes with time when each cell is used to provide an electric current lead acid cell cell x e m f v e m f v time hours time hours f i give one reason why the e m f of the lead acid cell changes after several hours mark f ii identify the type of cell that behaves like cell x mark f iii explain why the voltage remains constant in cell x marks extra space wmp jun chem

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