RI Electrochemistry 1 Tutorial - Answers to Self-check Questions

6 ANSWERS TO SELF-CHECK QUESTIONS 1 (a) The standard electrode potential, E, of a half–cell is the electromotive force, measured at 298 K, between the half–cell and the standard hydrogen electrode , in which the concentration of any reacting species in solution is 1 mol dm–3 and any gaseous species is at a pressure of 1 bar. (b) The standard cell potential (Ecell) is the potential difference between two half–cells under standard conditions. 2 (a) Checklist for the general labels to include when drawing the setup: in each half-cell connecting 2 half-cells identit y of electrode external wire with voltmeter identit y and concentration of electrolyte direction of electron flow gas jar, identity and partial pressure of gas (if any) salt brid ge temperature Note: Question may also ask for the labelling of anode (–) or cathode (+). (b) Set up the electrochemical cell as shown above. Read off the Ecell value on the voltmeter. The greater the Ecell value, the greater the difference in electrode potentials of the two half-cells. Monitor the direction of the flow of electrons to identify the electrode that is positively charged (the one to which electrons are flowing towards). The electrode that is positively charged contains the stronger oxidising agent which is preferentially reduced. (c) Cl2 (g) + 2I (aq)  I2 (aq) + 2Cl(aq) 3 (a) reduction half cell: C l2 / Cl (b) Cl2 + Co  2Cl + Co2+ (c) Ecell = +1.36 – (–0.28) = +1.64 V