Calcium phosphate, molar solubility

Compare and Contrast Which of the two solids, calcium phosphate or iron(lll) phosphate, has the greater molar solubility Ksp (Ca3(P04)2) = 1.2 x 10 Ksp (FeP04) = 1.0 X 10 . Which compound has the greater solubility, expressed in grams per liter ... 

Depending on the calcium/ phosphorus (Ca/P) molar ratio and solubility of the compound, it is possible to obtain numerous calcium phosphates of different composition. Molar Ca/P ratio and solubility are connected with the pH of the solution. Majority of materials of this class are resorbable and dissolve when inserted in a physical environment. Calcimn phosphates that are most frequently used in the biomaterial field are demonstrated in Table 1 (Dorozhkin, 2009c El Kady, 2009 Shi, 2006). 

What is the molar solubility of calcium phosphate, given that = 2.0 x 10 Assuming that the density of the samrated solution is 1.00 g/cm what is the solubility in grams of Ca3(P04)2 per 100 grams of solvent ... 

This means that the molar solubility of calcium phosphate is 1.1 x 10 M. Now convert units to find the solubility in terms of mass. 

Using data from Table 17.2, calculate the molar solubility of calcium phosphate, which is a component... 

Sodium tripolyphosphate, in particular, is unanimously recognized as an excellent builder that works by sequestering calcium and producing soluble species. However, it is crucial for the proportion used to be great enough (1 mol of TPP per mole of Ca)— otherwise, precipitations will occur. There exist many possible species of Ca TPP, particularly pentacalcium phosphate, a highly insoluble product that forms when the Ca/TPP molar ratio is greater than 1. 

Modes of passive degradation are not different from what we can observe in other aqueous media. We may, for example, observe a dissolution at grain boundaries associated with the release of particles and hydrolysis phenomena, sometimes limited to the siuface of the material. In the case of multiphase ceramics, phenomena connected to the transfer of material between phases of different solubility may appear. The release of particles in tissues or biological fluids may sometimes produce inflammatory reactions which we will analyze later. Certain plasma sprayed coatings of calcium phosphate can be associated with small proportions of calcium oxide, whose hydration is accompanied by a large increase in molar volume, leading to the formation of cracks and to a detachment from the metallic substrate. 

In the past, many variations of the sol-gel process have been developed and used to produce powders with different Ca/P ratios, by altering not only the quantity and composition of precursors but also the processing variables. As the synthesis of HA requires a calcium to phosphorus molar ratio of 1.67 1 in the final product, a number of caldum/phosphorus precursor combinations have been used in the preparation of HA powders. For example, calcium nitrate or different calcium alkoxides and 2-ethyl-hexyl phosphate, triethyl phosphate or orthophos-phoric acid, have been used as the calcium and phosphoras precursors, respectively. The major limitation for appUcation of the sol-gel process was shown to be the very poor solubility of the calcium alkoxides in organic solvents, and the poor reactivity of the phosphorous compounds. The effective control of stoichiometry due to the volatility of the phosphorous compounds used also represented a challenge. 

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