Lead fluoride, solubility product

Self-Test 11.11B The solubility product of lead(Il) fluoride, PbF, is 3.7 X 10 s. Estimate the molar solubility of the salt. 

Solving for [F"] gives a value of 1.4 x 10 M, which is correct choice (B). Forgetting to take the square root of [F-] leads to incorrect choice (D). Choice (A) fails to use the equilibrium constant expression at all, and assumes that calcium ions and fluoride ions are present in equimolar concentrations. Choice (C) results from squaring the calcium ion concentration before dividing it into the value for the solubility-product constant... 

Fluorinated chalcogenolates have been investigated as an alternative approach to the synthesis of soluble products. The Teflon-like character of tiie C6F5 moiety reduces intermolecular attractions and leads to the formation of hydrocarbon-soluble products. Thiolates have been investigated most extensively, and there are descriptions of both Ln(SC6F5)2 and Ln(SC6F5)3. These compounds have to be prepared with transmetallation reactions (Reaction 7), because attempts to reductively cleave disulfide bonds with elemental Ln leads to the formation of metal sources that appear to be passivated with a fluoride film. 

Solubility product. The solubility of lead fluoride, PbF , in water is 0.064 g/100 ml solution at 20°C. Calculate its solubility product... 

In general, saliva (as well as plaque fluid) is supersaturated with respect to calcium-phosphate salts, and they prevent tendency to dissolve mineral crystals of teeth. Moreover, precipitation of calcium-phosphate salts that include hydroxyapatite may also occur (remineralization) in early lesions of tooth surfaces injured by acidic bacterial products (i.e., lactic acid). Salivary fluoride facilitates calcium-phosphate precipitation, and such crystals (i.e., fluorapatite) show lower acid solubility properties that lead to an increased caries preventive effect. The increase of pFI (i.e., buffer capacity and pH of saliva, as well as ureolysis in dental plaque) also facilitates crystal precipitation and remineralization (4, 13). 

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