AQA Jan 2011 Paper 5 Q5

Answers available below

do not write outside the box a lithium ion cells are used to power cameras and mobile phones a simplified representation of a cell is shown below li li li coo licoo pt the reagents in the cell are absorbed onto powdered graphite that acts as a support medium the support medium allows the ions to react in the absence of a solvent such as water the half equation for the reaction at the positive electrode can be represented as follows li coo e li coo a i identify the element that undergoes a change in oxidation state at the positive electrode and deduce these oxidation states of the element element oxidation state oxidation state marks a ii write a half equation for the reaction at the negative electrode during operation of the lithium ion cell mark a iii suggest two properties of platinum that make it suitable for use as an external electrical contact in the cell property property marks a iv suggest one reason why water is not used as a solvent in this cell mark wmp jan chem do not write outside the box b the half equations for two electrodes used to make an electrochemical cell are shown below clo so aq h aq e cl aq h o i e v aq h aq e so aq h o i e v b i write the conventional representation for the cell using platinum contacts marks b ii write an overall equation for the cell reaction and identify the oxidising and reducing agents overall equation oxidising agent reducing agent marks turn over for the next question turn over wmp jan chem

Show answer