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Calculate the overpotential of a lead electrode in contact with a solution containing [Pb2+] = 0.001 M when the temperature is 298 K. Given that the standard potential of the Pb2+ / Pb electrode is -0.13 V and the exchange current density is 0.015 A/m2.

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ago by (650 points)
To calculate the overpotential of a lead electrode, we need to use the Tafel equation, which relates the overpotential    to the current density  i  and the exchange current density  i0 : =  2.303 * R * T  /  n * F  * log10 i / i0 where R is the gas constant  8.314 J/molK , T is the temperature  298 K , n is the number of electrons transferred in the redox reaction  2 for Pb2+ / Pb , and F is the Faraday constant  96485 C/mol .First, we need to calculate the equilibrium potential  E  using the Nernst equation:E = E0 +  R * T  /  n * F  * log10 [Pb2+] where E0 is the standard potential of the Pb2+ / Pb electrode  -0.13 V  and [Pb2+] is the concentration of Pb2+ ions  0.001 M .E = -0.13 +  8.314 * 298  /  2 * 96485  * log10 0.001 E  -0.13 +  0.043  * log10 0.001 E  -0.13 - 0.086E  -0.216 VNow, we need to find the current density  i  at this equilibrium potential. Since the exchange current density  i0  is given as 0.015 A/m2, we can use the Tafel equation to find the overpotential   : =  2.303 * 8.314 * 298  /  2 * 96485  * log10 i / 0.015 We can rearrange the equation to solve for i:i = 0.015 * 10^ *  2 * 96485  /  2.303 * 8.314 * 298  Since the overpotential    is the difference between the equilibrium potential  E  and the standard potential  E0 : = E - E0 = -0.216 -  -0.13  = -0.086 VNow, we can plug this value back into the equation for i:i = 0.015 * 10^ -0.086  *  2 * 96485  /  2.303 * 8.314 * 298  i  0.015 * 10^-0.086 * 23.15 i  0.015 * 10^-1.99 i  0.015 * 0.0102i  0.000153 A/m2Finally, we can plug this value of i back into the Tafel equation to find the overpotential   : =  2.303 * 8.314 * 298  /  2 * 96485  * log10 0.000153 / 0.015   0.043 * log10 0.0102   0.043 *  -2   -0.086 VSo, the overpotential of the lead electrode in contact with a solution containing [Pb2+] = 0.001 M at 298 K is -0.086 V.

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