Copper sulfate solutions

Fehling s solution (sugar detection and estimation) (a) Copper sulfate solution dissolve 34.639 g of CUSO4 5H2O in water and dilute to 500 mL. (b) Alkaline tartrate solution dissolve 173 g of rochelle salts (KNaC40g dHjO) and 125 g of KOH in water and dilute to 500 mL. Equal volumes of the two solutions are mixed just prior to use. The Methods of the Assoc, of Official Agricultural Chemists give 50 g of NaOH in place of the 125 g KOH. 

Aqueous ammonia also acts as a base precipitating metallic hydroxides from solutions of their salts, and in forming complex ions in the presence of excess ammonia. For example, using copper sulfate solution, cupric hydroxide, which is at first precipitated, redissolves in excess ammonia because of the formation of the complex tetramminecopper(TT) ion. 

Another process, which also generates elemental sulfur as a by-product, has been patented by Envirotech Research Center in Salt Lake City (29). In the Electroslurry process, a ball mill finely grinds a chalcopyrite concentrate, which reacts with an acidic copper sulfate solution for iron removal. The Hquor is electrolyzed and the iron is oxidized to the ferric form. This latter step leaches copper from the copper sulfide for deposition on the cathode. Elemental sulfur is recovered at the same time. 

This product is pure enough for most purposes. It gives no precipitate with copper sulfate solution, indicating the absence of the open-chain acid. ... 

If only a CU-CUSO4 electrode is available, the housing should always be filled with saturated copper sulfate solution, be free from bubbles, and be emptied before reuse the copper rod must be cleaned down to bare metal and refilled. 

Zinc-Copper Couple A 500-ml Erlenmeyer flask equipped for magnetic stirring is charged with a mixture of zinc powder (49.2 g, 0.75 g-atom) and hydrochloric acid (40 ml of 3 % aqueous solution). The contents of the flask are rapidly stirred for 1 minute, and the liquid is decanted. Similarly, the zinc is washed with the following three times with 40 ml of 3% hydrochloric acid solution, five times with 100 ml of distilled water, five times with 75 ml of 2 % aqueous copper sulfate solution, five times with 100 ml of distilled water, four times with 100 ml of absolute ethanol, and five times with 100 ml of absolute ether. These last ethanol and ether washes are decanted onto a Buchner funnel to prevent loss. The residue is collected by suction filtration, washed again with anhydrous ether, and dried in air. Finally, the zinc-copper couple is stored (20-24 hours) in a vacuum desiccator over phosphorous pentoxide. 

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,... 

Of course, as time goes on the copper sulfate solution in the cell has to be replaced because it collects undesirable ions such as Fe+2, which have not been reduced because the voltage used is favorable to the reduction of Cu+2 only. 

In this reaction, the more active zinc replaces the less active copper from solution. The reaction is evident because the blue color of the copper sulfate solution slowly turns colorless and a deposit of copper can be seen to form on the strip of zinc. 

How many electrons does a copper ion in copper sulfate solution take from a cathode in electroplating ... 

Dissolution is based on displacement Zinc sulfide in copper sulfate solution ZnS + Cu2+ -> Zn2+... 

Chemical process having the characteristic basing on displacement involves, for example, dissolution of a sulfidic substance in a solution holding a metal ion that yields a less-soluble sulfidic substance. The dissolution of zinc sulfide in copper sulfate solution is a worthwhile example that can be taken in the present context. In analyzing the reaction, reference first is drawn to the final reaction as shown below ... 

A knowledge of the extraction equilibria between the organic and aqueous phases helps to identify the operational variables that can control the solvent extraction process. An example - the extraction of copper from a copper sulfate solution using a chelating reagent (HR) - is considered. This is one of the best studied examples of solvent extraction. Normally, the system would not be described as a water-hydrocarbon dual-phase system, as it is in fact the Cu2+, SO-, H+, R-, and R-, and the equation... 

Because electrons are neither products nor reactants in chemical reactions, the two processes are interdependent and neither can occur alone. The zinc metal dissolution must furnish electrons for the copper metal plating. The reaction of zinc and copper sulfate solution is a spontaneous reaction involving a transfer of electrons, i.e., is a spontaneous redox process. The spontaneity of the reaction is commonly explained by saying that zinc loses electrons more readily than copper or, alternatively, that Cu2+ ions gain electrons more readily than Zn2+ ions. 

It represents the case of the reaction at the metal electrode in which ions of the same metal discharge at the electrode from the electrolyte. It can be said that copper ions in the electrolyte (copper sulfate solution) possess a free energy GCu(ej, and those in the copper metal electrode possess a free energy Ci(ll(-ril.. Then, if a copper ion is to leave its place in the copper sulfate electrolyte structure and occupy a position in the structure of the copper electrode, the free energy change accompanying this process will be ... 

Polyquats can easily be mixed with copper sulfate. The rule is first dilute the quat and subsequently add the copper sulfate solution afterwards. 

The rotating hemisphere electrode has been used to investigate the effect of AC on the electrodissolution and deposition reactions of zinc in zinc chloride [25] and copper in acid copper sulfate solutions [55], AC was found to increase the rate of nucleation and produce more uniform deposit on the zinc electrode. The corrosion of an iron rotating hemisphere in dilute sulfuric acid was investigated by Haili [31] using the AC impedance measurement. 

Fig. 4. Current density for the reduction of copper and the double layer capacity of a copper electrode in an acidic copper sulfate solution vs. applied overpotential (adapted from ref. 50).

The slow addition of aqueous ammonia solution to an aqueous copper sulfate solution causes an immediate effect on the solubility, since essentially all the Cu2+ ion is consumed by the hydroxide ion of the added reagent, forming in the process a product of very low solubility ... 

Cuprammonium A process for making regenerated cellulose fibers. Cellulose, from cotton or wood, is dissolved in ammoniacal copper sulfate solution (Schweizer s reagent, also called cuprammonium sulfate). Injection of this solution into a bath of dilute sulfuric acid... 

FIGURE 7.13 The absorption spectrum, visible region, of a copper sulfate solution. 

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