A student wants to calculate the corrosion rate of a zinc electrode in contact with a copper electrode, with a measured current of 0.5 amperes and a surface area of 2 cm². Given that the standard reduction potentials for copper and zinc electrodes are +0.34 V and -0.76 V, respectively, what is the corrosion rate of the zinc electrode in millimeters per year? (Assume a density of 7.14 g/cm³ for zinc and a Faraday constant of 96,500 coulombs per mole).

Question

A student wants to calculate the corrosion rate of a zinc electrode in contact with a copper electrode, with a measured current of 0.5 amperes and a surface area of 2 cm². Given that the standard reduction potentials for copper and zinc electrodes are +0.34 V and -0.76 V, respectively, what is the corrosion rate of the zinc electrode in millimeters per year? (Assume a density of 7.14 g/cm³ for zinc and a Faraday constant of 96,500 c

Answer 1

To calculate the corrosion rate of the zinc electrode, we need to determine the mass loss rate of zinc and then convert it to the thickness loss rate.First, we need to find the equivalent mass of zinc that is being corroded by the 0.5 A current. The reaction for the zinc electrode is:Zn  Zn + 2eThe number of moles of electrons  n  involved in this reaction is 2. The Faraday constant  F  is 96,500 C/mol. We can use the current  I  and Faraday's law to find the mass loss rate of zinc:I = n * F *  mass loss rate  /  molar mass of Zn Rearranging the equation to find the mass loss rate:mass loss rate = I *  molar mass of Zn  /  n * F The molar mass of zinc is 65.38 g/mol. Plugging in the values:mass loss rate = 0.5 A *  65.38 g/mol  /  2 * 96,500 C/mol mass loss rate  0.169 g/sNow, we need to convert the mass loss rate to the thickness loss rate. We can use the density    of zinc and the surface area  A  of the electrode:thickness loss rate =  mass loss rate  /   * A The density of zinc is 7.14 g/cm, and the surface area is 2 cm. Plugging in the values:thickness loss rate =  0.169 g/s  /  7.14 g/cm * 2 cm thickness loss rate  0.0118 cm/sTo convert the thickness loss rate to millimeters per year:thickness loss rate = 0.0118 cm/s *  10 mm/cm  *  60 s/min  *  60 min/h  *  24 h/day  *  365 days/year thickness loss rate  3733.68 mm/yearSo, the corrosion rate of the zinc electrode is approximately 3733.68 mm/year.