Question

Calculate the anodic Tafel slope for the following electrochemical reaction taking place at a platinum electrode:Fe2+(aq) + 2e- → Fe(s) Given that the exchange current density is 4.50 x 10^-4 A/cm^2 and the reaction rate constant for the reaction is 2.5 x 10^5 cm/s.

Answer 1

To calculate the anodic Tafel slope, we first need to determine the transfer coefficient    for the reaction. The transfer coefficient can be calculated using the following equation: = n * F * k /  2.303 * R * T where n is the number of electrons transferred in the reaction  in this case, n = 2 , F is the Faraday constant  96485 C/mol , k is the reaction rate constant  2.5 x 10^5 cm/s , R is the gas constant  8.314 J/molK , and T is the temperature in Kelvin  assuming room temperature, T = 298 K . = 2 * 96485 *  2.5 x 10^5  /  2.303 * 8.314 * 298   0.5Now that we have the transfer coefficient, we can calculate the anodic Tafel slope  b_a  using the following equation:b_a =  2.303 * R * T  /   * n * F b_a =  2.303 * 8.314 * 298  /  0.5 * 2 * 96485 b_a  0.119 V/decadeSo, the anodic Tafel slope for the given electrochemical reaction is approximately 0.119 V/decade.