Solubility Rules - for Ionic Compounds
Name: _________________
One form of evidence of a chemical reaction is the formation of a solid precipitate from two aqueous
solutions. In order to determine if two reactants will react (and form a precipitate), you must know how
to determine if the products are soluble or insoluble. We use “solubility rules” to make these
determinations. You must learn/memorize these solubility rules to be successful in AP Chemistry.
You will have three assignments in order to help you learn these rules:
1) Using the rules below, Complete the Chart: Exercise #1 – Names and Formulas with Solubility
2) Using the rules below, Complete the Chart: Exercise #2 – Making a Solubility Chart
3) Use your chart and rules, Complete Worksheet: Exercise #3 – Solubility Worksheet
MORE - Solubility Rules Charts
Positive Ions
(Cations)
Alkali Ions
(Li+, Na+, K+, Rb+,
Cs+, Fr+)
hydrogen ion
[H+ (aq)]
ammonium ion
(NH4)
any cation
NH4
H+(aq),
Negative Ions
(Anions)
=
Solubility of
Compounds in water
any anion
+
=
soluble
+
any anion
=
soluble
+
any anion
=
soluble
=
soluble
=
soluble
+
any cation
(except Ag)
alkali ions (Li+, Na+,
K+, Rb+, Cs+, Fr+),
+ and
+
+
Nitrate
NO3acetate
(CH3COO-)
hydroxide
OH-
+
=
Example
Sodium fluoride, NaF,
is soluble
hydrogen chloride, HCl,
is soluble
ammonium chloride,
NH4Cl, is soluble
potassium nitrate,
KNO3, is soluble
sodium acetate,
CH3COONa, is soluble
soluble
strontium hydroxide,
Sr(OH)2, is soluble
soluble
ammonium phosphate,
(NH4)3PO4, is soluble
soluble
sodium chromate, Na2CrO4,
is soluble
Sr2+, Ba2+, Ra2+, Tl+
alkali ions (Li+, Na+,
K+, Rb+, Cs+, Fr+),
Carbonate (CO32-),
+
and H+(aq), NH4
(Li+,
Sulfite (SO3
Na+,
alkali ions
K+, Rb+, Cs+, Fr+),
=
2-)
Chromate
+
Ca2+, Sr2+, NH4+,
Ag+, Pb2+, Hg2+,
Cu+, Tl+
Ag2+, Pb2+, Hg2+
Ba2+, Sr2+, Ca2+,
Phosphate (PO43-),
+
+
CrO42Chloride (Cl-),
Bromide (Br-),
Iodide (I-)
Sulfate
(SO42-)
=
(insoluble)
=
low solubility
(insoluble)
=
low solubility
silver chloride, AgCl,
white precipitate
barium sulfate, BaSO4,
forms a white precipitate
General Solubility Trends:








1) All compounds of the ammonium ion (NH4+), and of the Alkali metal (Group IA) cations, are soluble.
2) All nitrates and actetates are soluble.
3) All chlorides, bromides, and iodides are soluble EXCEPT those of silver, lead, and mercury(I).
4) All sulfates are soluble EXCEPT those of silver, lead, mercury(I), barium, strontium, and calcium.
5) All carbonates, sulfites, and phosphates are insoluble EXCEPT those of ammonium and Alkali metal (Group IA) cations.
6) All hydroxides are insoluble EXCEPT those of ammonium, barium, and alkali metal (Group IA) cations.
7) All sulfides are insoluble EXCEPT those of ammonium, Alkali metal (Group I) cations, and Alkali earth metal (Group II) cations.
8) All oxides are insoluble EXCEPT those of calcium, barium, and Alkali metal (Group I) cations; these soluble ones actually react
with the water to form hydroxides.
1. Salts containing Group I elements are soluble (Li+, Na+, K+, Cs+, Rb+). Exceptions to this rule are rare. Salts containing the
ammonium ion (NH4+) are also soluble.
2. Salts containing nitrate ion (NO3-) are generally soluble.
3. Salts containing Cl -, Br -, I - are generally soluble. Important exceptions to this rule are halide salts of Ag+, Pb2+, and (Hg2)2+.
Thus, AgCl, PbBr2, and Hg2Cl2 are all insoluble.
4. Most silver salts are insoluble. AgNO3 and Ag(C2H3O2) are common soluble salts of silver; virtually anything else is insoluble.
5. Most sulfate salts are soluble. Important exceptions to this rule include BaSO4, PbSO4, Ag2SO4 and SrSO4 .
6. Most hydroxide salts are only slightly soluble. Hydroxide salts of Group I elements are soluble. Hydroxide salts of Group II
elements (Ca, Sr, and Ba) are slightly soluble. Hydroxide salts of transition metals and Al3+ are insoluble. Thus, Fe(OH)3,
Al(OH)3, Co(OH)2 are not soluble.
7. Most sulfides of transition metals are highly insoluble. Thus, CdS, FeS, ZnS, Ag2S are all insoluble. Arsenic, antimony,
bismuth, and lead sulfides are also insoluble.
8. Carbonates are frequently insoluble. Group II carbonates (Ca, Sr, and Ba) are insoluble. Some other insoluble carbonates
include FeCO3 and PbCO3.
9. Chromates are frequently insoluble. Examples: PbCrO4, BaCrO4
10. Phosphates are frequently insoluble. Examples: Ca3(PO4)2, Ag3PO4
11. Fluorides are frequently insoluble. Examples: BaF2, MgF2 PbF2.
Exercise #1 – Names and Formulas (with Solubility)
1.
2.
Name or give the chemical formula for each of the following compounds.
State whether they are soluble (will dissolve) or insoluble (will not dissolve) in solution. Use solubility rules.
Chemical Formula
1. NH4CH3COO
2. Ba(OH)2
3.
4. NaOH
5. RbNO3
6.
7. MgSO4
8. ZnCl2
9.
10. Zn3(PO4)2
11. AgBr
12. KNO3
13. Al2S3
14.
15. Sr2CrO4
16.
17. BaSO4
18. Ca(OH)2
19. BaCO3
20. MgCrO4
21.
22. NH4CN
23.
24. Hg2SO4
25.
Name
Iron (II) Carbonate
Cesium Sulfate
Zinc Hydroxide
Silver Acetate
Aluminum Phosphate
Iron (III) sulfide
Silver Iodide
Lithium Chloride
Solubility (S) or Insoluble (I)
EXERCISE #2 – Making a Solubility Chart
Name: _______________
Using ONLY the rules on the first page, complete the chart below. Enter “S” for Soluble and “I” for insoluble.
NOTE: there may be some items that are NOT on your rules page. Additionally, there are “other” exceptions that
are “less common”. After you complete the chart ONLY using the rules, please check out a couple of the web links
below to make any needed corrections. NOTE: there will be some “—“ where the compound is neither “S” or “I”.
Br-
Cl-
ClO3- C2H3O2-
CO3-
CrO42-
F-
I-
NO3-
O2-
OH-
PO43-
S2-
SO32- SO42-
Ag+
Al3+
Ba2+
Ca2+
Co2+
Cu2+
Fe3+
Hg2+
K+
Li+
Mg2+
Na+
NH4+
Ni+
Pb2+
Sr2+
Zn2+
**Use these sites below to make CORRECTIONS to your chart above. Pay special attention to those boxes that
have either a “D” or “—“ as these are special exceptions to the rules:
http://en.wikipedia.org/wiki/Solubility_chart
http://c7chemistry.wikispaces.com/Solubility+rules
http://faculty.sdmiramar.edu/fgarces/ChemComon/CourseOutline_200/Ch200Info/ch200info.htm
EXERCISE #3 – Solubility Worksheet
After completing the first two exercises, you should now be more familiar with the more common ions
and their rules. Please note that you are going to be tested on these rules the first week you return.
The following questions will be similar to those on your test. Please make sure that you are able to
answer all of these questions without the use of an index card, as you will not be able to use any notes
on the test. An additional list of rules and examples are attached, followed by the answer key.
1. Classify each of the substances as being soluble or insoluble in water.
a.
b.
c.
d.
e.
f.
g.
h.
KBr =
PbCO3 =
BSO3 =
zinc hydroxide =
sodium acetate =
silver iodide =
cadmium (II) sulfide =
zinc carbonate =
i. silver acetate =
j. copper (II) sulfide =
k. Mg3(PO4)2 =
l. KOH =
m. NiCl2 =
n. NH4OH =
o. Hg2SO4 =
p. PbI2 =
2. Complete the following table by identifying the two new compounds (products) which would be
produced if the two aqueous solutions were to be mixed and undergo a double replacement reaction.
For each reaction, CIRCLE the name of the product that would form an insoluble precipitate.
KBr
AgNO3
BaCl2
Al(NO3)3
CuSO4
Na2CO3
CaS
NH4OH
ANSWER SHEET - EXERCISE #3 – Solubility Worksheet
1.Classify each of the substances as being soluble or insoluble in water.
a.
b.
c.
d.
e.
f.
g.
h.
potassium bromide – sol
lead (II) carbonate – insol
barium sulfate – insol
zinc hydroxide – insol
sodium acetate – sol
silver iodide – insol
cadmium (II) sulfide – insol
zinc carbonate – insol
i.
j.
k.
l.
m.
n.
o.
p.
silver acetate – sol
copper (II) sulfide – insol
Mg3(PO4)2 – insol
KOH – sol
NiCl2 - sol
NH4OH – sol
Hg2SO4 – insol
PbI2 – insol
3. 2. Complete the following table by identifying the two new compounds (products) which would be
produced if the two aqueous solutions were to be mixed and undergo a double replacement reaction.
For each reaction, CIRCLE the name of the product that would form an insoluble precipitate.
KBr
Na2CO3
CaS
NH4OH
AgBr + KNO3
NaNO3 +
Ag2CO3
Ca(NO3)2 +
Ag2S
AgOH + NH4NO3
KCl + BaBr2
N/R
(Both Insoluble)
AlBr3 + KNO3
N/R
(Both Insoluble)
NaCl + BaCO3
CaCl2 + BaS
Ba(OH)2 + NH4Cl
CuBr2 + K2SO4
N/R
(Both Insoluble)
Na2SO4 +
CuCO3
AgNO3
BaCl2
Al(NO3)3
CuSO4
NaNO3 +
Al2(CO3)3
Ca(NO3)2 +
Al2S3
CuS + CaSO4
NH4NO3 +
Al(OH)3
(NH4)2SO4 +
Cu (OH)2