Now that we have established a background on solubility, how do we know, and more importantly, how do we predict if a precipitate will form? Let's first analyze the criteria for precipitation and use this information to determine that if two solutions are mixed together if a precipitate would form.
Criteria For Precipitation
If Two Solutions are Mixed Will a Precipitate Form?
Now that we know how to determine if a precipitate will form, we can build on this information to determine the order in which precipitates will form. Consider a solution containing two different anions, when a cation is added drop wise (slowly) a precipitate will form the moment that Q > Ksp. Since salts have differing Ksp values, precipitates can form at different concentrations. The next example enables us to calculate the minimum concentration necessary to facilitate precipitation and to determine the concentration that will allow for the best separation.
Order of Precipitation, Minimum Concentration Needed to Facilitate Precipitation, and Best Separation
With the lectures notes from today you should be able to complete the following problems:
Precipitation Tutorial
Selective Precipitation Tutorial
Precipitation Calculation Tutorial
Fractional Precipitation of Metal Carbonates Tutorial
*Solubility Quiz Question #3
Questions 58-69 from the Solubility homework set posted on Carmen.
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