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
NO3acetate
C2H3O22
Chloride
ClAg+, Hg2+2, Pb+2
sulfate
SO4-2
Ba+2, Pb+2, Hg2+2, Ag+
chlorate
ClO3
perchlorate
ClO41
all Group I metals
2
Also, binary compounds of Br- and I- with metals are soluble. Exceptions are the same
as with Chloride.
Insoluble
Hydroxide
Oxide
Phosphate
Carbonate
Sulfide
Sulfite
Silicate
Silver
-
OH
O-2
PO4-3
CO3-2
S-2
SO3-2
SiO3-2
Ag+
Exceptions (Soluble)
*, Ba+2, Ca+2, Sr+2
*, Ba+2, Ca+2, Sr+2
*
*
*
*
*
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+ + NO3Complete 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+ + NO3The 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
2. MgCl2
3. LiNO3
4. Al(NO3)3
5. NH4Cl
6. NaC2H3O2
7. (NH4)2S
8. Zn(OH)2
9. Ag2SO4
10. ZnS
11. Fe(OH)3
12. Pb(NO3)2
13. Na2CO3
14. KOH
15. AgCl
16. CaSO4
17. AgNO3
18. ZnCO3
19. KI
20. Hg2(C2H3O2)2
21. K2SO4
22. BaO
23. Ag3PO4
24. Ba(OH)2
25. Hg2Cl2
26. SnC2H3O2
27. SrO
28. Hg2SO4
29. BaCl2
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
2. soluble
3. soluble
4. soluble
5. soluble
6. soluble
7. soluble
8. insoluble
9. insoluble
10. insoluble
11. insoluble
12. soluble
13. soluble
14. soluble
15. insoluble
16. soluble
17. soluble
18. insoluble
19. soluble
20. soluble
21. soluble
22. soluble
23. insoluble
24. soluble
25. insoluble
26. soluble
27. soluble
28. insoluble
29. soluble
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