Physical Chemistry Experiment: Electrochemistry Copper Electroplating Objective
ID: 229069 • Letter: P
Question
Physical Chemistry Experiment: Electrochemistry Copper Electroplating Objective Observe the electroplating process of various metals. Introduction After silver, copper possess the highest electrical conductivity of all metals (K = 59.62 S.n.mm-2) and therefore the demand for copper is correspondingly high The conductivity of copper is, however, strongly dependent on the purity. The degree of purity greater than 99.9 % required in electrical engineering can be obtained using electrolysis. The crude copper (refined copper, degree purity of 97-99 %) is cast to form 3-5 cm thick anode plates and is deposited as pure copper (99.98 %) on cathodes consisting of copper sheets. The less noble metals (metals with a more negative potential) contained in the crude copper, such as iron and zinc dissolve and remain in solution since the low electrolysis voltage of 0.25-0.30 V is not sufficient for these metals to be deposited. When the crude copper anode dissolves, the more noble metals (with a more positive potential than copper) such as silver, gold and platinum, precipitate as insoluble anode slime, from which they can subsequently be isolated in pure form by electrolysis. Due to the low current density (20 mA/cm2), the refining process usually takes several weeksExplanation / Answer
Weight of electrodes is different before and after the electrolysis process. This is because of the copper deposition according to Faraday's law.
1) When Cu and brass is used: Cu dissolutes from the brass (Cu+Zn) to solution in the form of ions, When the reductio potential is applied, it gets deposited on the cathode i.e pure copper foil to increase its weight. And the weight of brass decreases due to copper dissolution