Copper sulfate electrolysis

The numerical data that were collected by the students in the copper sulfate electrolysis practicals can be used now as an application of Faraday s laws. 

The law may be expressed in an another fashion by stating that the same quantity of electricity is required to liberate 1 g-equiv. of any product of electrolysis. This quantity of electricity is known as the Faraday, and is 96,500 coulombs. To elaborate, let the passage of the same quantity of electricity through two solutions, one of copper sulfate and the other of silver nitrate, be considered. According to Faraday s third law, the ratio of the weights of the copper and the silver deposited is equal to the ratio of the equivalent weights of these two metals. Ionically, the deposition reaction for the two metals considered can be shown as... 

The influence of antimony at a level of 300 ppm in copper electrolysis is also significant. The morphologies of deposits made from a pure acid-copper sulfate electrolyte and from an identical solution to which the antimony was added are shown in Figures 5 and 6. There are many other combinations of impurities and electrolytes which exhibit this changing surface appearance and deposit orientation besides those selected as examples. Anion effects are also not uncommon, with the halogens often causing the more notable changes. 

B. Perform the electrolysis in part A with the copper sulfate electrolyte heated to... 

Figure 11.16 Schematic of copper recovery by coupled transport from dump leach streams. The concentrated copper solution produced by coupled transport separation of the dump leach liquid is sent to an electrolysis cell where copper sulfate is electrolyzed to copper metal and sulfuric acid...

Copper in contact mass plays the role of a catalyst. Pure copper is obtained by the electrolysis of copper sulfate. For direct synthesis, we use the copper of two brands, Mo and Mi with 99.95-99.9% of Cu. The total impurity content (Bi, Sb, As, Fe, Ni, Pb, etc.) should not exceed 0.05-0.1%. To ensure high activity of contact mass, it is necessary to use copper powders with complex surfaces. Good results in direct synthesis are also obtained when using fine copper prepared by the mechanical spraying of copper powder or deposition of copper from copper salts. 

Purification of metals is another important application of electrolysis. For example, impure copper from the chemical reduction of copper ore is cast into large slabs that serve as the anodes for electrolytic cells. Aqueous copper sulfate... 

A 1.0 molar solution of copper sulfate is electrolyzed with an inert, e.g., platinum, anode and a copper cathode of 55 sq. cm. exposed area the current is maintained constant at 0.040 amp. If the electrolysis vessel contains 1 liter of solution and there is reasonable circulation of the electrolyte, without resort to stirring, estimate approximately how long electrolysis will proceed before hydrogen evolution commences. How much of the original copper will then have been deposited ... 

The major technical factors in electrorefining are cathode purity, production rate, and specific energy consumption. These factors are influenced primarily by anode quality, electrolyte conditions, and cathode current density. The electrolysis is performed in a solution of copper sulfate and sulfuric acid with a nominal composition of40-45 g L-1 copper and 160-200 g L-1 sulfuric acid at 60-66 °C with a current... 

To illustrate the Hittorf method for measuring the contribution of the individual ions to the current, we consider the electrolysis cell shown in Fig. 31.4. Suppose that the solution contains copper sulfate and that the anode is copper. We examine the changes that occur in each compartment if one mole of electricity passes. These changes are summarized in Table 31.4. If a quantity of electricity Q passes, this is Q/F moles, so all of the changes are... 

Copper is deposited as the element on a weighed Pt cathode from a solution of copper sulfate in an electrolytic cell. If a constant current of 0.600 A is used, how much Cu can be deposited in 10.0 min (Assume no other reductions occur and that the reaction at the anode is the electrolysis of water to produce oxygen.)... 

Conductance is usually given in the unit Siemens (S = 0 ). The validity of Ohm s law for the case of electrolyte solutions can be experimentally proven (Experiment 21.3 showing electrolysis of a copper sulfate solution with copper electrodes). 

When copper is extracted, in a process similar to that happening in the blast furnace, it is very impure. To purify the copper, it is used as the anode in a very large electrolysis cell containing copper sulfate solution as the electrolyte and a pure copper rod as the cathode. During the process, the anode dissolves and pure copper is deposited on the cathode. The impurities settle at the bottom of the cell. A simplified version of this process can be carried out as a class practical. 

The second law is ejq)lained in a straightforward manner by using the submicroscopic model of electrolytes to interpret the electrolysis phenomenon. In the case of copper deposited on the cathode in the electrolysis of copper sulfate solution, this model is expressed symbolically by the equation of the corresponding reduction half reaction ... 

In his creation of the first electric battery in 1799, Alessandro Volta laid the foundation of electrochemistry. His battery consisted of a zinc and a copper electrode dipped into an aqueous solution of sulfuric acid and connected externally by copper wires. The procedure for setting up and running this experiment is similar to the earlier practical of the electrolysis of aqueous copper sulfate solution (page 265), but without the external power supply. If a voltmeter is connected in parallel to the external circuit, it can be used to measure the potential difference. The half reactions and the overall reaction are as follows ... 

This condition is met in a method called internal electrolysis (or spontaneous electrogravimetric analysis), first described by Ullgren in 1868, in which electrolysis occurs by spontaneous discharge of a galvanic cell. To illustrate the principle, consider two half-cells, comprising a zinc rod in a zinc sulfate solution and a copper rod in a copper sulfate solution. At open circuit, 25 °C, the reversible cell potential is related to the two standard electrode potentials (E°) ... 

These anodes are used extensively in electrogalvanizing, tin electroplating, electrochemical production of copper foil for printed circuit boards, and electrowinning of copper and zinc [91-95]. The application of oxide-coated anodes to sodium sulfate electrolysis so far is small and is not a major driver of electrode development programs. However, environmental concerns associated with byproduct or waste sodium sulfate, along with possible imbalances in the demand for chlorine and caustic soda are enough to maintain interest in the technique. 

Copper sulfate may be analyzed by gravimetry by exhaustive electrolysis at a weighed platinum electrode. Add 2 mL H2SO4, 1 mL HNO3, and 1 g urea to 25 mL of the copper solution. 

The fluoride ISE is used routinely for measuring fluoridated water and fluoride ion in dental products such as mouthwash. A 50 mL aliquot of water containing sodium fluoride is analyzed using a fluoride ion electrode and the MSAs. The pH and ionic strength are adjusted so that all fluoride ion is present as free F" ion. The potential of the ISE/reference electrode combination in a 50 mL aliquot of the water was -0.1805 V. Addition of 0.5 mL of a 100 mg/L F ion standard solution to the beaker changed the potential to -0.3490 V. Calculate the concentration of (1) fluoride ion and (2) sodium fluoride in the water sample. Copper is deposited as the element on a weighed Pt cathode from a solution of copper sulfate in an electrolytic cell. If a constant current of 0.600 A is used, how much Cu can be deposited in 10.0 min (Assume no other reductions occur and that the reaction at the anode is the electrolysis of water to produce oxygen.)... 

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