Keep practicing, trust the equilibrium, and use guided inquiry to build lasting chemical intuition.
If you know the concentration of the ion already in the beaker, you solve for the concentration of the ion you are adding. Precipitation begins the moment the exceeds the Kspcap K sub s p end-sub . 3. Determining Which Ion Precipitates First A classic POGIL question might look like this: "A solution contains 0.10 M Cl−cap C l raised to the negative power and 0.10 M Br−cap B r raised to the negative power Ag+cap A g raised to the positive power is added, which silver salt forms first?" Step 1: Look up Kspcap K sub s p end-sub AgClcap A g cap C l AgBrcap A g cap B r Step 2: Calculate the needed to precipitate each. Answer: Since AgBrcap A g cap B r has a much lower Kspcap K sub s p end-sub