1. Ch 18 Notes II Precipitation Reactions

2. Solubility Rules The solubility rules will tell you if a compound will be soluble in water. Note, this does not tell us how soluble it is, just whether or not it will dissolve.

4. Soluble or Insoluble? NaNO 3 KClO 4 PbBr 2 K 2 CrO 4 Ca(OH) 2 Fe 2 S 3 AgCl Na 3 PO 4 Hg 2 SO 4 Fe(CN) 3 Ba(C 2 H 3 O 2 ) 2 SrS

5. Precipitation Precipitation is the formation of a solid in a solution during a chemical reaction. The precipitate is the solid formed due to creation of an insoluble compound. The remaining liquid is called the supernatant.

6. Lead (II) nitrate and potassium iodide solutions are mixed together. The yellow stuff is a solid, insoluble compound. What could it be?

7. The positive lead ion could go with the negative iodide ion and the positive potassium ion could go with the negative nitrate ion. Are either of the resulting compounds insoluble?

8. PbI 2 is insoluble, KNO 3 is not, so we say lead (II) iodide precipitates!

9. What precipitate forms between: Barium nitrate and sodium sulfate Potassium chloride and silver acetate Ca(ClO 3 ) 2 and (NH 4 ) 2 CrO 4 KClO 4 and Li 2 Cr 2 O 7 FeCl 3 and Ba(OH) 2

10. Net Ionic Equations We have already seen that when an ionic compound dissolves, it is broken into its positive and negative ions.

11. Net Ionic Equations A net ionic equation shows how the ions in a solution react together, instead of the entire compounds, ignoring ions that do not react. Ions that do not undergo reaction, but stay in solution are called spectator ions. NOTE: The following slide is a simplification—we will revisit this later!

12. Write the net ionic equation for the reaction: Write the ions that could react. Write insoluble products together as a compound and soluble products as ions. Cancel any ions on both sides. Insoluble compounds are marked with an (s) for solid.

13. Solutions of potassium chromate and silver nitrate are combined. Write the reactants as ions K + + CrO 4 2- + Ag + + NO 3 -  Determine the products K + +CrO 4 2- +Ag + + NO 3 -  K + + NO 3 - +Ag 2 CrO 4 (s) Cross out ions that don’t change K + +CrO 4 2- +Ag + + NO 3 -  K + + NO 3 - +Ag 2 CrO 4 (s)

14. Ag + +CrO 4 2-  Ag 2 CrO 4 (s) Balance by adding coefficients to the ions as needed. 2Ag + +CrO 4 2-  Ag 2 CrO 4 (s) Solutions of potassium chromate and silver nitrate are combined.

15. Write the net ionic equation for combination of solutions of: Calcium chlorate and sodium phosphate Sodium bromide and silver acetate (NH 4 ) 2 S and Al(NO 3 ) 3