Calcium fluoride solubility-product constant

We often shorten the term solubility product constant to solubility product. Thus, the solubility products for barium sulfate, BaS04, and for calcium fluoride, Cap2, are written as... 

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... 

The solubility product constant is equal to the product of the concentrations of the ions in a saturated solution, each concentration raised to a power equal to its coefficient (number of moles of individual ions formed per mole of the compound) in the balanced equation.Take a look at the solubility product equation of calcium fluoride (CaF ). 

Write the solubility product constant expression for calcium fluoride. 

The mineral fluorite is calcium fluoride, Cap2. Calculate the solubility (in grams per liter) of calcium fluoride in water from the solubility product constant... 

Alternatively, antisealants can be used to control calcium carbonate scale at LSI values as high as 2.0-2.5, depending on the specific antisealants. Calcium also forms scales with fluoride, sulfate, and phosphate. The LSI will not help predict these scales analysis of water quality, using the ion product and solubility constants, is required to determine the potential for scaling with calcium fluoride or calcium phosphate. Antisealants currently available can address calcium fluoride and calcium sulfate scale they do not address calcium phosphate scale (although newer antisealants will be available in the near future to address this scale). 

Calcium fluoride scale can form when the concentration of fluoride is as low as 0.1 ppm if the concentration of calcium is high. Scaling will occur when the ion product exceeds the solubility constant. Antisealants or sodium softening can be used to control calcium fluoride scale. 

The solubility product of calcium fluoride at 25°C is 3.9 x 10" . What was the resistance reading when the cell constant was 0.100 cm" Ignore the conductance contribution of the water. 

Calcium phosphate has become a common problem with the increase in treatment of municipal waste-water for reuse. Surface waters can also contain phosphate. Calcium phosphate compounds can contain hydroxyl, chloride, fluoride, aluminum, and/ or iron. Several calcium phosphate compounds have low solubility, as shown in Table 7.2. Solubility for calcium carbonate and barium sulfate are also shown by comparison. The potential for scaling RO membranes with the calcium phosphate compounds listed in Table 7.2 is high and will occur when the ion product exceeds the solubility constant. This can occur at orthophosphate concentrations as low as 0.5 ppm. Sodium softening or antisealants together with low pH help to control phosphate-based scaling. 

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