Iodides, solubility product

The solubility of copper(II) iodide, Cul2, is 0.004 g/liter. Determine the value of the solubility product. 

It is evident that silver iodide, being less soluble, will be precipitated first since its solubility product will be first exceeded. Silver chloride will be precipitated when the Ag+ ion concentration is greater than... 

Other useful solid-state electrodes are based on silver compounds (particularly silver sulfide). Silver sulfide is an ionic conductor, in which silver ions are the mobile ions. Mixed pellets containing Ag2S-AgX (where X = Cl, Br, I, SCN) have been successfiilly used for the determination of one of these particular anions. The behavior of these electrodes is determined primarily by the solubility products involved. The relative solubility products of various ions with Ag+ thus dictate the selectivity (i.e., kt] = KSp(Agf)/KSP(Aw)). Consequently, the iodide electrode (membrane of Ag2S/AgI) displays high selectivity over Br- and Cl-. In contrast, die chloride electrode suffers from severe interference from Br- and I-. Similarly, mixtures of silver sulfide with CdS, CuS, or PbS provide membranes that are responsive to Cd2+, Cu2+, or Pb2+, respectively. A limitation of these mixed-salt electrodes is tiiat the solubility of die second salt must be much larger than that of silver sulfide. A silver sulfide membrane by itself responds to either S2- or Ag+ ions, down to die 10-8M level. 

Out of the three compounds, silver chloride is the most soluble and silver iodide is the least soluble. (You can compare the solubilities of the compounds based on their solubility products because they are all the same type. Each formula unit contains two ions.)... 

Figure 6-3 Total solubility of lead(ll) (curve with circles) and solubilities of individual species (straight lines) as a function of the concentration of free iodide. To the left of the minimum, [Pb]tota, is governed by the solubility product for Pbl2(s). As [I ] is increased, [Pb]total decreases because of the common ion effect. At high values of [I ], Pbl2(s) redissolves because it reacts with I to form soluble complex ions, such as PblJ. Note logarithmic scales. The solution is made slightly acidic so that [PbOH+] is negligible.

Silver iodide particles in aqueous suspension are in equilibrium with a saturated solution of which the solubility product, aAg+ai, is about 10 16 at room temperature. With excess 1 ions, the silver iodide particles are negatively charged and with sufficient excess Ag+ ions, they are positively charged. The zero point of charge is not at pAg 8 but is displaced to pAg 5.5 (pi 10.5), because the smaller and more mobile Ag+ ions are held less strongly than-the 1 ions in the silver iodide crystal lattice. The silver and iodide ions are referred to as potential-determining ions, since their concentrations determine the electric potential at the particle surface. Silver iodide sols have been used extensively for testing electric double layer and colloid stability theories. 

Lead iodide (PbL) dissolves in water with solubility product... 

Methylation- or combined methylation-ethylation reactions were used for structure analysis of polysaccharides. The alkylation of dextran can be applied to the investigation of the branching pattern, i.e. the number and length of side chains (Sect. 2.2) [22,23]. The methylation is carried out in liquid ammonia with sodium iodide and methyl iodide, yielding products that are soluble in chloroform and tetrachloroethane [257]. 

Treatment of an epoxide, namely methyl 2,3-anhydro-4,6-0-benzylidene-oi-D-allopyranoside (78, Scheme 21), with nitryl iodide using methanol as the solvent has been reported.123 Rather than the expected nitration, opening of the epoxide occurred to afford 30% of methyl 4,6-0-benzylidene-3-0-methyl-oi-D-glucopyranoside (79), 10% of methyl 4,6-0-benzylidene-2-0-methyl-a-D-altropyranoside (80), and a water-soluble material. The water-soluble material was later determined to be a mixture of the 2-0- (81) and 3-0-methyl (82) products, with the benzylidene acetal removed, a result consistent with a later study.124 Performing the reaction in the absence of the silver salt resulted solely in formation of the water-soluble product. The preponderance of the diequatorial product 81 is in violation of the Flirst-Plattner rule, which predicts more of the diaxial product. The authors explanation for the anti-Fiirst-Plattner addition is as follows. 

The hydrolysis of the ammonium carbonate in aqueous solution gives rise to free dilute ammonia solution in which silver chloride, but not silver bromide or silver iodide, is appreciably soluble. The addition of bromide ions to the solution of silver chloride in ammonia results in the solubility product of silver bromide being exceeded, and precipitation occurs. 

Some of the earliest studies of organolanthanide chemistry described reactions of the elemental metals with alkyl and aryl iodide reagents (RI) (67). Analysis of the soluble products obtained for Ln = Eu, Yb, Sm indicated a formula of primarily RLnl although it was acknowledged that this could represent a number of different species in equilibrium. The amount of contamination of the divalent product with trivalent species was observed to follow the order of stability of the divalent states the Eu system was the cleanest, while the Sm system had only 50% of the metal in the divalent state. These species reacted like Grignard reagents. The... 

What would you expect to happen if 1 g of finely powdered silver iodide were stirred into a 1 F solution of sodium chloride The solubility-product constants are given in Table 22-1. 

Would lead chloride or lead iodide precipitate first if a solution of lead acetate were added drop by drop to a solution 1 M in chloride ion and 1 M in iodide ion What would be the composition of the solution when the second salt began to precipitate The solubility products are given in Table 22-1. 

EXAMPLE 7-6 Calculate the solubility of silver iodide in 0.01 M ammonia, if the solubility product of silver iodide is 9 x 10 and the logarithms of the successive formation constants of the silver-ammonia complexes are 3.2 and 3.8. 

Colloidal dispersions owe their stability to a surface charge and the resultant electrical repulsion of charged particles. This charge is acquired by adsorption of cations or anions on the surface. For example, an ionic precipitate placed in pure water will reach solubility equilibrium as determined by its solubility product, but the solid may not have the same attraction for both its ions. Solid silver iodide has greater attraction for iodide than for silver ions, so that the zero point of charge (the isoelectric point) corresponds to a silver ion concentration much greater than iodide, rather than to equal concentrations of the two ions. The isoelectric points of the three silver halides are ° silver chloride, pAg = 4, pCl = 5.7 silver bromide, pAg = 5.4, pBr = 6.9 silver iodide, pAg = 5.5, pi = 10.6. For barium sulfate the isoelectric point seems to be dependent on the source of the product and its de ee of perfection. ... 

In measurements with ion-selective electrodes, interference by other ions is expressed by selectivity coefficients as in Eq. (17). If the nature of the ion-selective membrane is known, these interferences may easily be estimated. For example, in the determination of chloride with a Cl -selective electrode containing AgCl as the electroactive component in its membrane, concentrations of bromides or iodides (generally X ) must be controlled because they form less soluble silver salts than AgCl the solubility products of corresponding silver halides are used in Eq. (20) to estimate the selectivity coefficient ... 

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