SrCO₃ has the smaller Ksp, so it will precipitate first. The [CO₃²⁻] required: for SrCO₃ = 5.6 × 10⁻⁹ M; for CaCO₃ = 3.4 × 10⁻⁸ M. Since the ratio is about 6:1, the separation is possible but less efficient than in previous examples.
For fractional precipitation, you systematically increase the concentration of the precipitating agent until Q exceeds Ksp for one salt, causing it to precipitate out, while the other salt remains in solution because Q is still below its Ksp.
will begin to precipitate when the silver ion concentration reaches . Part C: Determining the First Precipitate Comparing the two threshold concentrations: is a significantly lower threshold than , will precipitate first . Part D: Calculating the Remaining Ion Concentration
Compare the required silver ion concentrations:
To convert this into a percentage of the original chloride concentration remaining:
POGIL worksheets usually provide a reference table containing data similar to this: : : Critical Thinking Check: Even though has a smaller Kspcap K sub s p end-sub value numerical value, its stoichiometry is different (