Copper complexes ammines

Copper hydroxide is almost iasoluble ia water (3 p.g/L) but readily dissolves ia mineral acids and ammonia forming salt solutions or copper ammine complexes. The hydroxide is somewhat amphoteric dissolving ia excess sodium hydroxide solutioa to form ttihydroxycuprate [37830-77-6] [Cu(011)3] and tetrahydroxycuprate [17949-75-6] [Cu(OH) ]. ... 

As a general rule, the solubility of copper ammine complexes in water and alcohols increases with the rise in coordinating power of the amine concerned the molecular weight of the latter is also involved. The following general... 

Preparation of the desired copper ammine complex by metathesis in solution and addition of an organic precipitating solvent. 

Figure 12.20, Percent copper-ammine complexes as a function of NH3 (from Evangelou, 1997, unpublished data, with permission).

A considerable amount of work has been devoted to the action of ionizing radiation on polymeric carbohydrates in the solid state, in particular with regard to its effect on the mechanical properties even though some chemical effects have also emerged. For a recent review see [99]. Of these polymers, cellulose has been the most studied (c/. [99, 100]). Native cellulose is locally crystalline. Determination of chain breakage by radiolysis has usually been done after dissolution through complexation, e.g. as the copper-ammine complex (Schweizer s reagent), or the cadmium-ethylenediamine complex. 

Chemists frequently make a new compound and then analyze the new material in order to determine its formula. In this experiment you will prepare a copper-ammine complex, which is a coordination complex, and then you will analyze the complex for copper and ammonia. Your ultimate goal is to determine the copper-ammine ratio and the probable formula of the coordination complex and of the compound. 

The analysis of the copper-ammine complex for the ammonia, NH3, content will involve an acid-base "back titration." In this analysis, you will react the complex with an accurately measured volume of standardized hydrochloric acid, HCl, solution. The volume of HCl solution should be sufficient to react with all the ammonia and leave some excess HCl. The excess HCl will then be back reacted with standardized sodium hydroxide, NaOH, solution. The difference between the number of moles of HCl added and the number of moles of excess HCl will give the number of moles of ammonia in your measured quantity of copper-ammine complex. For your information, you cannot titrate the ammonia directly with HCl because of problems with seeing the color changes of the appropriate indicator in the presence of the colored copper-ammine complex. 

Place a cuvette containing distilled water into the cell compartment. (Alternatively, your instructor may designate that an indexed 13 x 100-mm test tube be used as the cuvette. The frosted identification mark on the cuvette, or the mark on your indexed test tube, must be directed toward the front of the instrument.) Adjust the wavelength dial to 600. nm, and then rotate the 100% control dial until the meter reads 100% T. Remove the cuvette, and replace it with the cuvette containing the solution of [Cu(H20)e]S04. Record the % T in TABLE 17.IE. Remove the cuvette, and replace it with the cuvette containing the solution of 0.5 M aqueous ammonia, NH3, as the "blank" to adjust the 100% T. Remove the cuvette, and replace it with the solution of the copper-ammine complex solution. Record... 

Perform the calculations in TABLE 17.2 including the sample calculations for one run on the pages following TABLE 17.2. In addition, plot % T (on the y-axis) versus wavelength in nm (on the x-axis) for [Cu(H20)g]S04 and for your copper-ammine complex, and estimate for each the wavelength of maximum absorbance (least transmittance) and the color which corresponds to that wavelength of maximum absorbance. 

Wavelength of maximum light absorption for copper-ammine complex (nm) ... 

A Percent yield of copper-ammine complex (to be calculated after you have determined the formula of the complex in part D)... 

D Moles of copper in copper-ammine complex (Remember that you did not titrate the entire sample of copper-ammine complex.)... 

Formula of copper-ammine complex (assuming one Cu per formula)... 

What is the oxidation state of copper in your copper-ammine complex Justify your answer. 

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