Silver moles

Figure 11. Uptake data for silver. ( ) Moles of Ag/cell X 10, (0) moles of Ag/g of cell X 1(F, ...

Last but not the least problem with unified approach to electrochemical processes across various states of matter is the use of molar fraction [25] as the unit of concentration in electrochemical equations. Such choice of the concentration unit implies that the EP would exhibit a very simple dependence on the presence of the so-called indifferent electrolyte. By this logic, the potential of Ag I Ag" " electrode in aqueous solution (e.g., 0.1 mol of silver nitrate) should depend on the addition of sodium nitrate since the molar fraction of silver ions is changed by the addition of the indifferent salt (KNO3) even if the molar-volumetric concentration of Ag+ ions remains constant. Moreover, the substitution of sodium salt with any other apparently indifferent salt (potassium, ammonium, alkyl-ammonium salt, etc.) is expected to shift the EP to new values. However, the indifferent (or supporting) electrolyte in common electrochemical practice is considered to be only affecting (stabilizing) the activity coefficient. On the other hand, the unanswered question persists whether the potentials of ideal silver-mercury and silver-gold alloy electrodes in silver nitrate solution are equal when silver mole fractions are equal, or when the silver molar-volumetric concentrations are equal. 

Strike couldn t find any decent nitroethane synths except for a couple of Chemical Abstract articles. One suggestion is to treat 1.5 moles of Na2C02 with 1 mole of sodium ethylsulfite and 0.0645 moles of K2CO3 at 125-130°C. Another route would be to use silver nitrate and ethyl iodide [8 p119]. This type of reaction has been used to nitrate other paraffins and would probably work. 

The nickel ion freed may then be determined by an EDTA titration. Note that two moles of silver are equivalent to one mole of nickel and thus to one mole of EDTA. 

Note that in writing this mass balance equation, the concentration of Ag(NH3)2i" must be multiplied by 2 since two moles of NH3 occurs per mole of Ag(NH3)2i". The second additional equation is a mass balance on iodide and silver. Since Agl is the only source of N and Ag+, every iodide in solution must have an associated silver ion thus... 

Oxidation of saligenin with chromic acid or silver oxide yields saUcyladehyde as the first product. Further oxidation results in the formation of sahcyhc acid, which is also obtained when saligenin is heated with sodium hydroxide at 200—240°C. Chlorination of an aqueous solution of the alcohol gives 2,4,6-trichlorophenol, and bromination in an alkaline medium yields 2,4,6-tribromophenol and tribromosaligenin. When saligenin is heated with one mole of resorcinol in the presence of anhydrous zinc chloride, 3-hydroxyxanthene forms. 

Only three simple silver salts, ie, the fluoride, nitrate, and perchlorate, are soluble to the extent of at least one mole per Hter. Silver acetate, chlorate, nitrite, and sulfate are considered to be moderately soluble. AH other silver salts are, at most, spatingly soluble the sulfide is one of the most iasoluble salts known. SHver(I) also forms stable complexes with excess ammonia, cyanide, thiosulfate, and the haUdes. Complex formation often results ia the solubilization of otherwise iasoluble salts. Silver bromide and iodide are colored, although the respective ions are colorless. This is considered to be evidence of the partially covalent nature of these salts. 

Na[AuClJ, per mole of silver haHde. Coordination compounds are used as emulsion stabilizers, developers, and are formed with the weU-known thiosulfate fixers. Silver haHde diffusion transfer processes and silver image stabilization also make use of coordination phenomena. A number of copper and chromium azo dyes have found use in diffusion transfer systems developed by Polaroid (see Color photography, instant). Coordination compounds are also important in a number of commercial photothermography and electrophotography (qv) appHcations as weU as in the classic iron cyano blueprint images, a number of chromium systems, etc (32). 

To a solution of 33 g. (O.S mole) of potassium hydroxide (Note 1) in 1.5 1. of distilled water in a 5-1. flask or other appropriate container fitted with a mechanical stirrer is added 80 g. (0.5 mole) of methyl hydrogen adipate (Note 2). With continuous stirring a solution of 85 g. (0.5 mole) of silver nitrate in 1 1. of distilled water is added rapidly (about IS minutes). The precipitated methyl silver adipate is collected on a Buchner funnel, washed with methanol, and dried in an oven at 50-60°. For the next step the dried silver salt is finely powdered and sieved through a 40-mesh screen. The combined yield from two such runs is, 213 g. (80%). 

The 213 g. (0.8 mole) of finely powdered silver salt is placed in a 1-1. three-necked flask (Note 3) two necks of the flask are stoppered, and the third is connected to a water pump through a U-tube or flask containing Drierite. The flask is then placed in an oil bath and evacuated to a pressure of about IS mm. The temperature of the oil bath is maintained at 100-110 for 36 hours (Notes 4 and S). 

A. Silver trifluoroacetate. To a suspension of 187 g. (0.81 mole) of silver oxide (Note 1) in 200 ml. of water is added 177 g. (1.55 moles) of trifluoroacetic acid (Note 2). The resulting solution is filtered, and the filtrate is evaporated to dryness under reduced pressure. The dry silver trifluoroacetate thus obtained is purified by placing it in a Soxhlet thimble and extracting with ether, or by dissolving the salt in 1.2 1. of ether, filtering through a thin layer of activated carbon, and evaporating the filtered ether solution to dryness. The yield of colorless crystalline salt obtained after removal of the ether is 300 g. (88%). 

The silver oxide was prepared by adding, with manual stirring, 66 g. of 98% sodium hydroxide (1.62 moles) in 2 1. of water to a solution of 274 g. (1.62 moles) of silver nitrate in 500 ml. of water. The precipitate was collected by filtration and washed with water until free from alkali. The wet cake can be dried or preferably used moist for reaction with trifluoroacetic acid. 

No systematic study of the minimal required amount of lead tetraacetate has been made. In cases where the product of the hypoiodite reaction is an iodo ether (20-hydroxy steroids) the reaction can be interrupted at the iodohydrin stage by reducing the amount of iodine to about 0.5 mole. For the oxidation of iodo ethers to lactones, chromium trioxide-sulfuric acid in acetone has been used. Silver chromate is often added to the reaction mixture but comparable yields are obtained without the addition of silver salt. 

Bromo-A-homo-estra-4y5 0)-diene-3, l-dione (49). A solution of silver perchlorate (0.55 g, 5 mole-eq) in acetone (2 ml) is added to a refluxing solution of monoadduct (48 0.28 g) in acetone (30 ml) containing water (0.5 ml). After being heated at reflux for 25 min the reaction mixture is cooled and the precipitated silver bromide is removed by filtration, yield about 0.11 g. The filtrate is diluted with water (500 ml) and is thoroughly extracted with chloroform. The chloroform extracts are washed with water and saturated salt solution, dried over anhydrous magnesium sulfate, and evaporated at... 

Similar measurements were made for the heat of precipitation of silver iodide,5 which is even less soluble in water than silver chloride. As shown in Table 33 in Sec. 102, a saturated solution of Agl at 25°C contains only 9.08 X 10-9 molcs/liter, as compared with 1.34 X 10-6 for AgCl. By calorimetric measurement the heat of precipitation of Agl at 25°C was found to be 1.16 electron-volts per ion pair, or 20,710 cal/mole. 

Returning now to silver chloride, let us apply these ideas to its saturated aqueous solution at 25°. From the value given in Table 42, we see that in solid AgCl the entropy per ion pair is almost exactly 1 milli-electron-volt per degree, which is equivalent to 23.0 cal/deg/mole. It makes no difference whether we express the entropies per ion pair in electron-volts per degree or in the equivalent calories per degree per mole. In the electrochemical literature the calorie per degree per mole is used and is called one entropy unit. (This is abbreviated e.u.) ... 

Since the saturated solutions of AgT and AgCl are both very dilute, it is of interest to examine their partial molal entropies, to see whether we can make a comparison between the values of the unitary terms. As mentioned above, the heat of precipitation of silver iodide was found by calorimetric measurement to be 1.16 electron-volts per ion pair, or 26,710 cal/mole. Dividing this by the temperature, we find for the entropy of solution of the crystal in the saturated solution the value... 

The heat of solution of silver bromide in water at 25°C is 20,150 cal/mole. Taking the value of the entropy and the solubility of the crystalline solid from Tables 44 and 33, find by the method of Secs. 48 and 49 the difference between the unitary part of the partial inolal entropy of the bromide ion Br and that of the iodide ion I-. 

As another example we may discuss silver iodide. As mentioned in Sec. 49 a saturated aqueous solution of this salt at 25°C contains only 9.08 X 10-9 mole in 1000 grams of water. At this low concentration the activity coefficient does not differ appreciably from unity we have then... 

The saturated solution of silver iodate in water at 25°C has a molality equal to 0.00179, and the activity coefficient y in this saturated solution may be taken to be 0.989. The heat of solution tends at extreme dilution to the value +13,200 c d/mole Find in electron-volts per ion pair the value of L, and also the value of dL/dT in water at 25°C. 

By x-ray diffraction it is possible to determine the geometric pattern in which atoms are arranged in a crystal and the distances between atoms. In a crystal of silver, four atoms effectively occupy the volume of a cube 0.409 nm on an edge. Taking the density of silver to be 10.5 g/cm3, calculate the number of atoms in one mole of silver ... 

In Experiment 8 you determined the number of moles of silver chloride formed in the reaction of some sodium chloride with a known amount of silver nitrate. How many moles of sodium chloride reacted with the silver nitrate Compare this with the number of moles of sodium chloride you added. 

For example, sodium chloride continues to dissolve in water at 20°C until the concentration is about six moles per liter. The solubility of NaCl in water is 6 M at 20°C. In contrast, only a minute amount of sodium chloride dissolves in ethyl alcohol at 20°C. This solubility is 0.009 M. Even in a single liquid, solubilities differ over wide limits. The solids calcium chloride, CaCl2, and silver nitrate, AgNOa, have solubilities in water exceeding one mole per liter. The solid called silver chloride, AgCl, has a solubility in water of only 10 5 mole per liter. 

Now let s be more quantitative. Let s repeat the experiment, weighing the metal rods before and after the test. The weighing shows that during the test the copper rod has become 0.63S gram lighter and the silver rod has become 2.16 grams heavier. Chemical reaction has occurred and, as any good chemist will do, we immediately ask, How many moles of copper and silver are involved ... 

We see that there is a simple relationship between the weight of copper dissolved and the weight of silver deposited. One mole of copper dissolves in the right beaker for every two moles of silver deposited in the left beaker. Copper ions, Cu+YaqJ, are formed in the right beaker from... 

The moles of silver deposited per mole of copper dissolved are the same whether reaction (J) is carried out in an electrochemical cell or in a single beaker, as in Experiment 7. If, in the cell, electrons are transferred from copper metal (forming Cu+2) to silver ion (forming metallic silver), then electrons must have been transferred from copper metal to silver ion in Experiment 7. 

Our conclusions are again in agreement with experiment. The cell operates so as to dissolve zinc metal and precipitate silver metal. The voltage is indeed about 1.5 volts. Finally, experiment shows that one mole of zinc does react with two moles of silver ion, as required by the balance of electrons. 

If you wish to replate a silver spoon, would you make it the anode or cathode in a cell Use half-reactions in your explanation. How many moles of electrons are needed to plate out 1.0 gram of Ag ... 

In Experiment 7, would the ratio between moles of copper atoms used and moles of silver atoms formed change if silver sulfate, Ag2S04, had been used rather than silver nitrate, AgN03 Explain. 

In a complex-formation reaction the equivalent is most simply deduced by writing down the ionic equation of the reaction. For example, the equivalent of potassium cyanide in the titration with silver ions is 2 moles, since the reaction is ... 

B. l,l-Diphenyl-2-bromo-Z-acetoxy- -j>ropene. A 250-ml. flask equipped with a condenser is charged with 17.6 g. (0.050 mole) of 1,1-dibromo-2,2-diphenylcyclopropane, 12.5g. (0.075 mole) of silver acetate [Acetic acid, silver(l +) salt] (Note 4), and 50 ml. of glacial acetic acid, then immersed in an oil bath at 100-120° for 24 hours (Note 5). After cooling, the mixture is diluted with 200 ml. of ether and filtered. The ethereal filtrate is washed with two 100-ml. portions of water, two 100-ml. portions of aqueous saturated sodium carbonate, and finally with two 100-ml. portions of water. After drying over anhydrous sodium sulfate, the ether is removed on a rotary evaporator. Distillation of the resulting residue under reduced pressure yields 12.0 g. (72%) of the product, b.p. 142-145° (0.15 mm.), 1.6020-1.6023 (Note 6). 

In a 250-ml., three-necked flask fitted with a mechanical stirrer, a thermometer, and a 25-ml., graduated, pressure-equalizing dropping funnel are placed 7.60 g. (0.050 mole) of phenoxyacetic acid [Acetic acid, phenoxy-] (Note 1), 5.40 g. (0.050 mole) of 1,4-benzoquinone [2,5-Cyclohexadiene-l,4-dioneJ (Note 2), 1 g. (0.006 mole) of silver nitrate [Nitric acid silver(l +) salt] (Note 3), and 125 ml. of water (Note 4). The mixture is then stirred and heated to 60-65° by means of a heating mantle until dissolution is complete. The resulting solution is stirred... 

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