Copper sulfate solution cell electrolyte

Now let s take a more detailed look into the electrochemical cell. Figure 12-5 shows a cross-section of a cell that uses the same chemical reaction as that depicted in Figure 12-1. The only difference is that the two solutions are connected differently. In Figure 12-1 a tube containing a solution of an electrolyte (such as KNOa) provides a conducting path. In Figure 12-5 the silver nitrate is placed in a porous porcelain cup. Since the silver nitrate and copper sulfate solutions can seep through the porous cup, they provide their own connection to each other. 

The copper obtained from this process is about 99% pure, yet this is not pure enough for most uses, especially those involving electrical conductivity. To refine the copper further, it is made the anode of an electrolytic cell containing copper sulfate solution. With careful control of the voltage to regulate the half-reactions that can occur, the copper is transferred from the anode (where it is about 99 % Cu) to the cathode where it can be deposited as 99.999% Cu. At the anode there is oxidation of copper,... 

During battery discharge, as shown in Figure 1 with the Daniell cell as an example, the electrode (a zinc rod immersed in a zinc sulfate solution) at which the oxidation reaction takes place is called the anode, and is the negative electrode. The other electrode (a copper rod immersed in a copper sulfate solution) at which the reduction reaction takes place is called the cathode and is the positive electrode. The electron flow in the external circuit is from anode to cathode (the current, /, conventionally flows in the opposite direction to that of the electrons), and in the electrolyte phase the ionic flow closes the circuit. The net result of the charge flow round the circuit is the cell reaetion, which is made up of the two half-reactions of charge transfer that describe the chemical changes at the two electrodes. 

As mentioned previously, the cell shown in Figure 22-1 has two liquid junctions, one between the silver nitrate solution and one end of the salt bridge, the other between the copper sulfate solution and the. salt bridge. Sometimes it is possible and advantageous to prepare cells in which the electrodes share a common electrolyte and thus eliminate the effect of junction potentials. An example of a cell of this type is shown in Figure 22-2, If the voltmeter were removed and replaced by a wire, silver would behave as the cathode. The reaction at the cathode would be... 

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.)... 

The half-cell generally used for cathodic protection in the field is the copper sulfate electrode. This consists of an electrode of electrolytic copper in a saturated solution of copper sulfate. The electrode can easily be made to have a large current capacity and will carry current better when it is acting as an anode than as a cathode. In the field, the cell is easily recharged and commercially pure copper sulfate solutions give potentials consistent to within 5 mV. 

The copper-copper sulfate reference electrode consists of copper metal immersed in a saturated copper sulfate solution, as shown in Fig. 2.9. A porous frit or wooden plug serves as an electrolytic contact with the cell. The electrode reaction is ... 

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 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.)... 

Section 23.4 Electrometallurgy is tire use of electrolytic methods to prepare or purify a metallic element. Sodium is prepared by electrolysis of molten NaCl in a Downs cell. Aluminum is obtained in the Hall process by electrolysis of AI2O3 in molten cryolite (NagAlFg). Copper is purified by electrolysis of aqueous copper sulfate solution using anodes composed of impure copper. 

In the Redox Chemistry of Iron and Copper movie (eChapter 23.8), copper from a copper sulfate solution is reduced and forms a coating of copper metal on an iron nail. Based on this observation, predict what would happen to an iron impurity in crude copper during the electrolytic refinement of copper. Would the iron be oxidized and become part of the electrolyte solution in the cell, or would it become part of the anode sludge Explain. 

The final processing in tire production of high-purity metals is often carried out electrolytically and is referred to as electrorefining. In this process the metal to be refined, such as copper or silver, has a typical initid purity of 95 to 99% and the aim is to reduce the impurity level to less than 0.1%. Conventional purification processes are often either inadequate or too expensive for this purpose. In electrorefining, the impure metal, e.g., copper, is placed in an electrolytic bath as an anodic plate that is paired with a cathode on which the purified metal is deposited electrolytically. The electrolyte typically consists of an aqueous solution of a salt of the metal to be purified, for example, copper sulfate, and the electrolytic cell is composed of an array of closely spaced alternating cathodes and anodes. A sample electrode pair and the configuration of the electrolytic cell are shown in Figure 3.2a. 

Salt Concentration Cells. In this type of cell the two electrodes are of the same metal (i.e., copper). These electrodes are immersed completely in electrolytes of the same salt solution (i.e., copper sulfate) but of different concentrations. When the cell is short circuited, the electrodes (anode) exposed to the dilute solution will dissolve into the solution and plate the electrode (cathode) exposed to the more concen-trated solution. These reactions will continue until the solutions are of the same concentration. Figure 4-432 shows a schematic of a salt concentration cell. 

In a Daniell cell, the pieces of metallic zinc and copper act as electrical conductors. The conductors that carry electrons into and out of a cell are named electrodes. The zinc sulfate and copper(II) sulfate act as electrolytes. Electrolytes are substances that conduct electricity when dissolved in water. (The fact that a solution of an electrolyte conducts electricity does not mean that free electrons travel through the solution. An electrolyte solution conducts electricity because of ion movements, and the loss and gain of electrons at the electrodes.) The terms electrode and electrolyte were invented by the leading pioneer of electrochemistry, Michael Faraday (1791-1867). 

You have learned that electroplating is a process in which a metal is deposited, or plated, onto the cathode of an electrolytic cell. In this investigation, you will huild an electrolytic cell and electrolyze a copper(II) sulfate solution to plate copper onto the cathode. You will use Faraday s law to relate the mass of metal deposited to the quantity of electricity used. 

The multilayered Cu/Co systems discussed here can be grown as described next (6b). Electrolyte composition is based on a cobalt/copper ratio of 100 1 and consists of a solution of 0.34 M cobalt sulfate, 0.003 M copper sulfate, and 30g/L boric acid. The pH is fixed around 3.0, and there is no forced convection while deposition is carried out. The electrodeposition may usually be carried out potentiostatically at 45°C between —1.40 V versus SCE for the cobalt and —0.65 V versus SCE for the copper with an 3 cell potential interrupt between the cobalt-to-copper transition to avoid cobalt dissolution, which can occur when there is no interrupt. 

Determine the amount (in moles) of electrons needed to produce the indicated substance in an electrolytic cell (a) 5.12 g of copper from a copper(II) sulfate solution (b) 200 g of aluminum from molten aluminum oxide dissolved in cryolite (c) 200 L of oxygen gas at 273 K and 1.00 atm from an aqueous sodium sulfate solution. 

Examples of electroplating, such as nickel plating. Use a nickel anode, a copper cathode and nickel sulfate solution as the electrolyte in a cell similar to that in Figure 5.20 (p. 84). 

Electrolytes are used in electrochemistry to ensure the current passage in -> electrochemical cells. In many cases the electrolyte itself is -> electroactive, e.g., in copper refining, the copper(II) sulfate solution provides the ionic conductivity and the copper(II) ions are reduced at the - cathode simultaneous to a copper dissolution at the - anode. In other cases of -> electrosynthesis or - electroanalysis, or in case of - sensors, electrolytes have to be added or interfaces between the electrodes, as, e.g., in case of the -> Lambda probe, a high-temperature solid electrolyte. 

The reversible back emf is the reversible emf of the galvanic cell set up by the passage of the electrolytic current, based on concentrations of solutes involved in the electrode reactions in the bulk of the solution. For example, if an acidic solution of copper sulfate is electrolyzed between platinum electrodes, the electrode reactions are... 

The component of the voltaic cell through which ions are able to flow is called the electrolyte. For our voltaic cell, the zinc sulfate solution is the electrolyte in the anode half-cell, and the copper(II) sulfate solution is the electrolyte in the cathode half-cell. 

Figure 14.6-1 Two types of electrochemical cells, (a) A cell with two electrodes and shared electrolyte. One example of such a cell contains a copper electrode, a zinc electrode, and a zinc sulfate and copper sulfate electrolyte solution. The overall cell reaction is Cu" (aq) -)- Zn(s) —> Cu(s) -f Zn" (aq). (b) A cell with two separate compartments connected by a salt bridge. If the same electrodes as in the previous case were used, one compartment would contain a copper electrode and a CuSO solution, the other would have a zinc electrode and a ZnS04 solution as the electrolyte, and the two compartments would be connected by a bridge containing, for example, a sodium chloride solution.

One beaker contains copper sulfate at a concentration of 0.0001 M and another contains a 0.01-M solution of the same salt. Compute the maximum voltage that could be obtained at 25° C with an electrochemical cell that used these two solutions as electrolytes. 

The current-voltage characteristic of an electrolytic cell was analyzed in Section 6.1, where the solution contained between the copper electrodes was cupric sulfate. Suppose that the cupric sulfate solution is replaced by another electrolyte which is indifferent to the electrodes that is, no chemical reactions take place at the electrode surfaces. A constant potential difference is applied across the electrodes. Determine the potential and concentration distributions in the solution between the electrodes. 

Daniell cell /dan-yel/ A type of primary cell consisting of two electrodes in different electrolytes separated by a porous partition. The positive eletrode is copper immersed in copper(II) sulfate solution. The negative electrode is zinc-mercury amalgam in either dilute sulfuric acid or zinc sulfate solution. The porous pot prevents mixing of the electrolytes, but allows ions to pass. With sulfuric acid the e.m.f. is... 

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