Drawing Exercises

What is the standard free energy change for this cell?

The following two half-reactions are used in a voltaic cell. A strip of silver metal is placed in a 1 M solution of silver nitrate, and a strip of nickel metal is placed in a 1 M solution of nickel nitrate. The metal strips are connected by a wire, and the solutions are connected by a salt bridge. Draw a sketch of the cell on a piece of paper and use this information for the exercises on this page. Ag+ + e– → Ag E°red = + 0.80V Ni2+ + 2e– →Ni E°red = −0.25V

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1. a voltaic cell has a positive voltage, even after reversing one of the reductions into an oxidation: oxid : Ni --> Ni2+ + 2e- E°oxid = +0.25V reduc: Ag+ + e– → Ag.......E°red = + 0.80V final voltage = 1.05 volts, even though we double the silver reaction to get 2 moles of electrons taken, to go along with the two moles of electrons lost by the Ni ----------- dG = -n F E = -(2moles of electrons)(96.5 kJ/Volt mol)(1.05 Volts)= -202.65 kJ ANSWER= - 203 kiloJoules (energy released)