Solubility Rules - South High School Library



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Bo Ram (Cathy) Kim

AP Chemistry 1998

Revised by:

Clete Albitz

Woo J (Richard) Kim

AP Chemistry 1999

Revised by:                 

Young Sang Cha

Karen Shu

Grace Song

AP Chemistry 2000

                           Revised and Improved by:

           Jason Lee

David Suh

           AP Chemistry 2001

Revised, Improved, and Perfected by:

Jacklyn Yoon

Jennifer Lim

Sara Nam

Stephanie Lin

AP Chemistry 2012

Solubility Rules

The following rules are used in several chemistry-related topics, such as predicting reactions and quantitative analysis. You will learn these topics this year in AP Chemistry but if you don’t know your solubility rules, you’ll have a really hard time. Solubility rules must be committed to memory. No, seriously. You might even be tested on it later!

|Soluble | |Exceptions (Insoluble) |

|ammonium |NH4+ | |

|Potassium1 |K+ | |

|Sodium1 |Na+ | |

|nitrate |NO3- | |

|acetate |C2H3O2- | |

|Chloride2 |Cl- |Ag+, Hg2+2, Pb+2 |

|sulfate |SO4-2 |Ba+2, Pb+2, Hg2+2, Ag+ |

|chlorate |ClO3- | |

|perchlorate |ClO4- | |

1 all Group I metals

2 Also, binary compounds of Br- and I- with metals are soluble. Exceptions are the same as with Chloride.

|Insoluble | |Exceptions (Soluble) |

|Hydroxide |OH- |*, Ba+2, Ca+2, Sr+2 |

|Oxide |O-2 |*, Ba+2, Ca+2, Sr+2 |

|Phosphate |PO4-3 |* |

|Carbonate |CO3-2 |* |

|Sulfide |S-2 |* |

|Sulfite |SO3-2 |* |

|Silicate |SiO3-2 |* |

|Silver |Ag+ |NO3- |

* Group IA metals and NH4+

All strong acids and strong bases will ionize, or separate into its ions when reacting with water, completely. The only strong acids are: HCl, H2SO4, HClO4, HI, HBr, and HNO3. The strong bases are: NaOH, LiOH, KOH, Li2O.

When you look at the solubility chart, you will notice that other bases, such as Ca(OH)2 and Ba(OH)2, are said to be soluble as well. However, except for the strong bases listed, all other bases are only SLIGHTLY soluble. Slightly soluble compounds mean that they will ionize only a little bit. To be safe, all bases, except for the strong bases listed above, should not be turned into its ions.

Also if one part of a compound is soluble but the other isn’t, then the whole compound is insoluble. For example, in AgClO3, ClO3- is soluble but Ag+ is not. Therefore, the whole compound is insoluble.

Precipitation Reactions

Solubility Rules are critical in the field of reactions, especially precipitation reactions. A precipitation reaction occurs when two soluble salts are added, forming an insoluble salt (the precipitate) and a soluble salt.

Soluble Salt + Soluble Salt ( Insoluble Salt + Soluble Salt

For each of the following, write the reactions. (Note: If you have not already memorized all the Solubility Rules, go back and memorize them and then come back to this.)

Separate the compounds into ions when they are soluble. Remember, strong acids and bases ionize completely; therefore they are separated into ions. Cross out common ions, which are also known as spectator ions. That’s the cool scientific term.

Don’t forget to balance the equation.

Ex: A solution of silver nitrate is added to a solution of potassium chloride.

Molecular Equation:

AgNO3 + KCl ( AgCl + KNO3

Molecular is basically what you get when you don’t ionize anything.

Complete Ionic Equation:

Ag+ + NO3- + K+ + Cl- ( AgCl + K+ + NO3-

Complete Ionic is when you ionize the compounds into their ions.

Net-Ionic Equation:

To get to the net-ionic form, cross out the spectator ions.

Ag+ + NO3- + K+ + Cl- ( AgCl + K+ + NO3-

The answer will then be:

Ag+ + Cl- ( AgCl

This is the form that AP classes will usually take, unless specified.

For this question, Silver chloride precipitates, or forms a solid because it does not ionize.

Assignment #8

I. Soluble or Insoluble?

Determine whether the following salts are soluble or insoluble. (Note: Try not to use your Solubility Rules chart. You will not be allowed to use the charts on your tests. So, try to learn and memorize the rules.)

Ex. KCl Answer: soluble

I. Solubility

1. NaOH 11. Fe(OH)3 21. K2SO4

2. MgCl2 12. Pb(NO3)2 22. BaO

3. LiNO3 13. Na2CO3 23. Ag3PO4

4. Al(NO3)3 14. KOH 24. Ba(OH)2

5. NH4Cl 15. AgCl 25. Hg2Cl2

6. NaC2H3O2 16. CaSO4 26. SnC2H3O2

7. (NH4)2S 17. AgNO3 27. SrO

8. Zn(OH)2 18. ZnCO3 28. Hg2SO4

9. Ag2SO4 19. KI 29. BaCl2

10. ZnS 20. Hg2(C2H3O2)2 30. Na2SiO3

II. Precipitation Reactions

1. A solution of silver nitrate is added to a solution of potassium bromide.

2. A solution of sodium carbonate is added to a solution of manganese (II) nitrate.

3. A solution of copper (II) nitrate is added to a solution of sodium carbonate.

4. A solution of calcium acetate is added to a solution of potassium fluoride.

5. A solution of lead (II) nitrate is added to a solution of potassium iodide.

6. A solution of barium chloride is added to a solution of sodium sulfate.

7. A solution of ammonium chloride is added to a solution of mercury (I) nitrate.

8. A solution of lithium acetate is added to a solution of iron (III) bromide.

9. A solution of zinc chloride is added to a solution of sodium hydroxide.

10. A solution of sodium hydroxide is added to a solution of iron (II) chloride.

11. A solution of silver nitrate is added to a solution of calcium chloride.

12. A solution of potassium phosphate is added to a solution of strontium sulfate.

13. A solution of potassium carbonate is added to a solution of zinc chloride.

14. A solution of copper (II) chloride is added to a solution of potassium sulfide.

15. A solution of lead (II) nitrate is added to a solution of lithium chloride.

16. A solution of sodium hydroxide is added to a solution of nickel (II) chloride.

17. Aqueous solutions of silver nitrate and ammonium phosphate are mixed.

18. Aqueous solutions of cobalt (II) acetate and calcium hydroxide are mixed.

19. Aqueous solutions of barium chloride and ammonium sulfate are mixed.

20. Aqueous solutions of potassium sulfide and iron (III) nitrate are mixed.

Answers:

I. Insoluble or Soluble?

1. soluble 6. soluble 11. insoluble 16. soluble 21. soluble 26. soluble

2. soluble 7. soluble 12. soluble 17. soluble 22. soluble 27. soluble

3. soluble 8. insoluble 13. soluble 18. insoluble 23. insoluble 28. insoluble

4. soluble 9. insoluble 14. soluble 19. soluble 24. soluble 29. soluble

5. soluble 10. insoluble 15. insoluble 20. soluble 25. insoluble 30. soluble

II. Precipitation Reactions

(The following answers are in the form of net ionic equations. Common ions are negligible.)

1. AgBr precipitates: Ag+ + Br- ( AgBr

2. MnCO3 precipitates: CO3-2 + Mn+2( MnCO3

3. CuCO3 precipitates: Cu+2 + CO3-2 ( CuCO3

4. CaF2 precipitates: Ca+2 + 2F- ( CaF2

5. PbI2 precipitates: Pb+2 + 2I- ( PbI2

6. BaSO4 precipitates: Ba+2 + SO4-2 ( BaSO4

7. Hg2Cl2 precipitates: 2Cl- + 2Hg+ ( Hg2Cl2

8. No precipitate because this isn’t a precipitation reaction. The soluble salt + soluble salt part is right, but those two don’t make an insoluble salt + soluble salt in this reaction. If you write it out, you should get: 3LiC2H3O2 + FeBr3 ( 3LiBr + Fe(C2H3O2)3. Everything in this reaction, from the reactant to the products, is soluble.

9. Zn(OH)2 precipitates: Zn+2 + 2OH- ( Zn(OH)2

10. Fe(OH)2 precipitates: 2OH- + Fe+2 ( Fe(OH)2

11. AgCl precipitates: Ag+ + Cl- ( AgCl

12. Sr3(PO4)2 precipitates: 2PO4-3 + 3Sr+2 ( Sr3(PO4)2

13. ZnCO3 precipitates: CO3-2 + Zn+2 ( ZnCO3

14. CuS precipitates: Cu+2 + S-2 ( CuS

15. PbCl2 precipitates: Pb2+ + 2Cl- ( PbCl2

16. Ni(OH)2 precipitates: 2OH- + Ni+2 ( Ni(OH)2

17. Ag3PO4 precipitates: 3Ag+ + PO4-3 ( Ag3PO4

18. Co(OH)2 precipitates: Co+2 + 2OH- ( Co(OH)2

19. BaSO4 precipitates: Ba+2 + SO4-2 ( BaSO4

20. Fe2S3 precipitates: 3S-2 + 2Fe+3 ( Fe2S3

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