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Mercury electrodes were pretty popular until they were found to be horribly toxi

ID: 825357 • Letter: M

Question

Mercury electrodes were pretty popular until they were found to be horribly toxic. Consider the Hg0electrochemical reaction

2Hg (l) + Fe(+2) (aq) + SO4 (-2) (aq) --> Hg2SO4 (s) + Fe (s) E' = -1.06 V

a) The following parameters were used to construct a cell at 298 K:

Chemical..............Concentration (mol/L)

FeCl2.....................0.100

Na2SO4.................0.100

The cell potential with the above conditions is -1.1302V. Using the Nernst equation

(E = E' - (RT/nF)ln(a_{prod}/a_{react}))   

Dervive the value of the mean activity coefficient of Fe(+2), gamma +/- (hint: n=2)

Explanation / Answer

Eo(redox) = Eo(oxidation) + Eo(reduction) X + Y+ ? X+ + Y