Zinc metal is commonly produced by electrowinning from acidic zinc sulphate solutions. (a) What are the materials of which the cathode blanks and the anodes are made? [3 marks] (b) Write balanced equations for the main reactions at the cathode (two) and the anode (one). [4 marks] (c) If the current density is 500A/m2 and the anode - cathode spacing is 50mm, calculate the ohmic voltage drop in the solution if the conductivity of the electrolyte is 0.5S/cm. [5 marks] (d) Calculate the overall cell voltage if the overpotential at the cathode was found to be 0.15V at 500A/m2 and the rate of the anode reaction was found to have a Tafel slope of 0.12V/ decade and an exchange current density of 10 12A/m2. The equilibrium electrode potentials for the cathode and anode reactions are 0.75V and 1.20V respectively versus NHE. [8 marks] (e) Calculate the cost of electrical power (in $/ tonne of zinc produced) for the electrolytic recovery of zinc if the cathode current efficiency is 90% and the cost of power is 15c/kWh. [5 marks] [For an anodic reaction, =blog10(i/i0),S=ohm1 ]