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Solubility Lesson 6 Separating Ions. Positive ions react with negative ions to give a precipitate if they have low solubility. A precipitate can be separated from a solution by filtration . The precipitate will be on the filter paper while the soluble ions will go through.
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Solubility Lesson 6 Separating Ions
Positive ions react with negative ions to give a precipitate if they have low solubility. A precipitate can be separated from a solution by filtration. The precipitate will be on the filter paper while the soluble ions will go through. To separate ions one ion must be low solubility and all others high.
Separating Positive Ions 1. Separate Ba2+ & Pb2+ Start at the top of page 4 and try Cl- first
Ba2+ 1st add Cl-, it reacts with Pb2+ (low) and not Ba2+(high) 2nd add SO42-, it reacts with Ba2+ (low)
NaCl Cl- Na+ Pb2+ NO3- Ba2+ PbCl2 Filter
Separating Positive Ions 1. Separate Ba2+ & Pb2+ i. Add NaCl Filter out PbCl2(s) Cl-does not exist on its own Add NaCl because it is soluble- always use Na+for negative ions Pb2+ + 2Cl- PbCl2(s) ii. Add Na2SO4 Filter out BaSO4(s) Ba2+ + SO42- BaSO4(s)
Separating Positive Ions 2. Separate Cu2+, Mg2+ & Sr2+
Cu2+ Sr2+ Cu2+ Mg2+ Mg2+ Mg2+ Cu2+
Separating Positive Ions 2. Separate Cu2+, Mg2+ & Sr2+ i. Add Na2SO4 Filter out SrSO4(s) Sr2+ + SO42- SrSO4(s) SO42-does not exist on its own Add Na2SO4 because it is soluble- always use Na+for negative ions ii. Add Na2S Filter out CuS(s) Cu2+ + S2- CuS(s) iii. Add NaOH Filter out Mg(OH)2(s) Mg2+ + 2OH- Mg(OH)2(s)
Separating Negative Ions Remove the lowest negative ionon the chart first by adding a positive cation. 3. Separate Cl- & OH- Look for a cation that is low with OH- (lowest)and high with Cl-.
Ba2+ Look for a cation that is low withwith Cl- Look for a cation that is low with OH- (lowest)and high with Cl-. Ba2+ Remove the lowest negative ion first by adding a positive cation.
Separating Negative Ions 3. Separate Cl- & OH- i.Ba2+works so add Ba(NO3)2and filteroutBa(OH)2(s) Ba2+ + 2OH- Ba(OH)2(s) Ba2+does not exist on its own Add Ba(NO3)2because it is soluble- always use NO3-to pair with positive ions ii.Add Ag+as AgNO3 and filter out AgCl(s) Ag+ + Cl- AgCl(s)
Separating Negative Ions 4. Separate Cl- S2- CO32-
Look for a cation that is low withwith Cl- Look for a cation that is low withS2-and high with Cl- Zn2+ Look for a cation that is low with CO2- and high with Cl- and S2- Ba2+
Separating Negative Ions 4. Separate Cl- S2- CO32- i.Ba2+works so add Ba(NO3)2and filteroutBaCO3(s) Ba2+ + CO32- BaCO3(s) Ba2+does not exist on its own Add Ba(NO3)2because it is soluble- always use NO3-to pair with positive ions ii.Add Zn2+as Zn(NO3)2 and filter out ZnS(s) Zn2+ + S2- ZnS(s) iii. Add Ag+as AgNO3 and filter out AgCl(s) Ag+ + Cl- AgCl(s)