1. Section 6.4—Solubility & Precipitation How can we make sure everything that’s added to the sports drink will dissolve?

2. A Review of Double- Replacement Reactions

3. NaCl + AgNO 3  AgCl + NaNO 3 Double Replacement Reactions The cations from two compounds replace each other. Cl Na Ag O O O O N N O O Cl Ag Na O O O O N N O O Two ionic compounds switch ions

4. Double Replacement Reactions General format of a double replacement reaction:

5. Combine the cation of the first reactant with the anion of the second reactant CaCl 2 +AgNO 3 1 Products of a Double Replacement

6. Combine the cation of the second reactant with the anion of the first reactant CaCl 2 +AgNO 3 2 Products of a Double Replacement

7. & balance charges with subscripts when writing formulas Remember to write cations first … AgCl CaCl 2 +AgNO 3 3 Ca(NO 3 ) 2 + CaCl 2 AgNO 3 + Products of a Double Replacement Only leave subscripts that are in the original compound there if they are a part of a polyatomic ion!

8. Precipitation Reactions

9. A precipitation reaction is when 2 soluble substances are mixed together and they form an insoluble substance 2 soluble chemicals: NaOH and Cu(NO 3 ) 2

10. Precipitation Reactions A precipitation reaction is when 2 soluble substances are mixed together and they form an insoluble substance 2 soluble chemicals: NaOH and Cu(NO 3 ) 2 2 soluble chemical: NaNO 3 1 insoluble chemical (the precipitate): Cu(OH) 2

11. Why do some things dissolve and others don’t?

12. Remember the dissolving process? Substances are dissolved by a process called hydration  The solvent and solute need to break intermolecular forces within themselves  New intermolecular forces are formed between the solvent and solute  The solvent “carries off” the solute particles

13. Review--Dissolving Ionic Compounds -+ + + + - -- - ++ -- O H H - + water Ionic compound Water molecules are polar and they are attracted to the charges of the ions in an ionic compound. When the intermolecular forces are stronger between the water and the ion than the intramolecular between the ions, the water carries away the ion.

14. -+ + - -- - + + Review--Dissolving Ionic Compounds ++ -- O H H - + water Ionic compound As more ions are “exposed” to the water after the outer ions were “carried off”, more ions can be “carried off” as well.

15. Review--Dissolving Ionic Compounds ++ -- O H H - + water Ionic compound -+ + + + - -- - These free-floating ions in the solution allow electricity to be conducted

16. What about with stronger ionic bonds? 2-2+ 2- ++ -- O H H 2+ water Ionic compound Ion charge can affect strength of ionic bond—the higher the charges, the stronger the bond. (How closely the two ions can pack together also affects ionic bond strength)

17. ++ -- O H H 2- 2+ water Ionic compound If the connection between the water and the ions is not similar in strength or stronger than the ion-ion and water- water connections that are being broken… What about with stronger ionic bonds? 2-2+ 2-

18. What about with stronger ionic bonds? 2-2+ 2- If the connection between the water and the ions is not similar in strength or stronger than the ion-ion and water- water connections that are being broken… The water won’t be able to carry the ions away…it won’t dissolve the solid. ++ -- O H H 2- 2+ water Ionic compound

19. Solubility Rules

20. Solubility Rules Table THESE ANIONS FORMS SOLUBLE COMPOUNDS WITH THESE CATIONS FORM INSOLUBLE COMPOUNDS WITH THESE CATIONS NO 3 - nitrateMost cationsNo common cations CH 3 COO – acetate Most cationsAg + Cl - chlorideMost cationsAg +, Pb 2+, Hg 2 2+, Tl + Br - bromideMost cationsAg +, Pb 2+, Hg 2 2+, Tl + I - iodideMost cationsAg +, Pb 2+, Hg 2 2+, Tl + SO 4 2- sulfateMost cationsBa 2+, Sr 2+, Pb 2+, Ag +, Ca 2+ CrO 4 2- chromate Most cationsBa 2+, Sr 2+, Pb 2+, Ag + S 2- sulfideNH 4 +, cations of column 1, cations of column 2 Most other cations OH - hydroxide NH 4 +, cations of column 1, and Ba 2+ and Sr 2+ Most other cations CO 3 2- carbonate NH 4 +, cations of column 1 except Li + Most other cations PO 4 3- phosphate NH 4 +, cations of column 1 except Li + Most other cations This table, found at the end of Chpt 6 and in the Appendix, can help you figure out which compounds dissolve (those that are soluble) and which form precipitate (insoluble)

21. Let’s Practice #1 Example: Decide whether each is soluble or not NaNO 3 AgCH 3 COO CaBr 2 Ba(OH) 2 Cu(OH) 2

22. Let’s Practice #1 Example: Decide whether each is soluble or not NaNO 3 AgCH 3 COO CaBr 2 Ba(OH) 2 Cu(OH) 2 Soluble Not soluble Soluble Not Soluble

23. Let’s Practice #2 Example: Write the products for this reaction Na 2 CrO 4 (aq) + BaCl 2 (aq)  Remember to indicate compounds that dissolve with “aq” for “aqueous” and compounds that don’t dissolve with “s” for “solid”

24. Let’s Practice #2 2 NaCl (aq) + BaCrO 4 (s) Example: Write the products for this reaction Na 2 CrO 4 (aq) + BaCl 2 (aq)  Remember to indicate compounds that dissolve with “aq” for “aqueous” and compounds that don’t dissolve with “s” for “solid”

25. Let’s Practice #3 Example: Write the products for this reaction NaCH 3 COO (aq) + KCl (aq)  Remember to indicate compounds that dissolve with “aq” for “aqueous” and compounds that don’t dissolve with “s” for “solid”

26. NaCH 3 COO (aq) + KCl (aq)  Let’s Practice #3 NaCl (aq) + KCH 3 COO (aq) Example: Write the products for this reaction Remember to indicate compounds that dissolve with “aq” for “aqueous” and compounds that don’t dissolve with “s” for “solid” When everything dissolves, there is no net reaction!