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Calculate the exchange current density for a zinc electrode immersed in a 1.0 M solution of zinc sulfate at 25°C when the overpotential is 0.05 V. The standard reduction potential for the Zn2+/Zn couple is -0.76 V. The transfer coefficient is 0.5. Assume that the concentration of the electrolyte does not change significantly during the reaction.

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To calculate the exchange current density  i0  for the zinc electrode, we can use the Tafel equation:i = i0 *  exp  * F *  / R * T  - exp - * F *  / R * T  where:i = current density  A/m i0 = exchange current density  A/m  = transfer coefficient  dimensionless F = Faraday's constant  96485 C/mol  = overpotential  V R = gas constant  8.314 J/molK T = temperature  K First, we need to convert the temperature from Celsius to Kelvin:T = 25C + 273.15 = 298.15 KNow, we can rearrange the Tafel equation to solve for i0:i0 = i /  exp  * F *  / R * T  - exp - * F *  / R * T  We are given the overpotential    as 0.05 V and the transfer coefficient    as 0.5. However, we do not have the current density  i  value. To find the current density, we can use the Nernst equation:E = E0 +  R * T /  * F  * ln [Zn2+]/[Zn] where:E = electrode potential  V E0 = standard reduction potential  V [Zn2+] = concentration of Zn2+ ions  M [Zn] = concentration of Zn atoms  M Since the concentration of Zn atoms is negligible compared to the concentration of Zn2+ ions, we can assume [Zn]  0. Therefore, the Nernst equation simplifies to:E = E0 +  R * T /  * F  * ln [Zn2+] We are given the standard reduction potential  E0  as -0.76 V and the concentration of Zn2+ ions as 1.0 M. We can now solve for the electrode potential  E :E = -0.76 +  8.314 * 298.15 /  0.5 * 96485   * ln 1.0 E = -0.76 VSince the overpotential    is given as 0.05 V, we can find the actual potential  E'  at the electrode:E' = E + E' = -0.76 + 0.05E' = -0.71 VNow, we can use the Butler-Volmer equation to find the current density  i :i = i0 *  exp  * F *  E' - E0  / R * T  - 1 Rearranging the equation to solve for i0:i0 = i /  exp  * F *  E' - E0  / R * T  - 1 We are given all the values except for the current density  i . Unfortunately, without the current density value, we cannot calculate the exchange current density  i0 . If you can provide the current density value, we can proceed with the calculation.

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