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Obtain a relation between standard cell potential ( or standard emf) and equilibrium constant of the cell reaction. |
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Answer» Solution :For any galvanic cell, the overall cell reaction at equilibrium can be represented as, Reactants `HARR`Products. [For example for Daniell cell,`Zn_((S) +Cu_((aq))^(2)) hArr Zn_((aq))^(2+) +Cu_((s))`] The equilibrium constant is related to the standard free energychange `DeltaG^(@)` as , follows. `DeltaG^(@) = - RT` in K If `E_("cell")^(0)` is thestandard cell potential (or emf) of the galvanic cell, then `DeltaG^(@) = - nFE_("cell)^(@)` By comparing above equations, `DeltaG^(@) = - nFE_("cell")^(@) = - RT In k` `therefore E_("cell")^(@) = (RT)/(nF)` In K OR `E_("cell")^(0) = (2.303 RT)/(nF) log_(10)` K At `25^(@)C` `(2.303 xx RT)/(F) = (2.303 xx 8314 xx 298)/(96500) = 0.0592` `therefore E_("cell")^(0) = (0.0592)/(n) log_(10)K` This is a relation between equilibrium constant and `E_("cell")^(0)` |
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