Solubility Rules
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1
2Solubility Rules
Use mnemonics to help you memorize these!! I’ll give you some suggested ones, but you don’t have to use them. Use
what works for you.
SOLUBILITY RULES (recall that soluble means will dissolve in water)
Always soluble (will always completely dissociate in water):
+
+
+
+
+
+
-
-
-
-
Alkali metal ions (Li
, Na
, K
, Rb
, Cs
), NH
, NO
, ClO
, ClO
, C
H
O
4
3
3
4
2
3
2
Generally soluble (will dissociate in water unless bonded to):
-
-
2+
+
2+
Cl
, Br
Soluble except Hg
Ag
Pb
2
,
,
-
2+
2+
+
2+
I
Soluble except Hg
Hg
Ag
, Pb
,
2
,
,
-
2+
2+
2+
2+
2+
F
Soluble except Sr
, Ba
, Ca
, Mg
Pb
,
2-
2+
2+
2+
2+
SO
Soluble except Sr
, Ba
, Ca
, Pb
4
Generally insoluble (will not dissociate in water unless bonded to):
2-
-
+
O
OH
Insoluble except alkali metals, and NH
,
4
,
2+
2+
2+
Ca
, Sr
, Ba
somewhat soluble
2-
2-
2-
2-
2-
2-
+
CO
, PO
, S
, SO
, C
O
, CrO
Insoluble except alkali metals and NH
3
4
3
2
4
4
4
+
Example 1: NaCl is soluble (will completely dissolve) because Na
is an alkali metal and is always soluble, but PbCl
is
2
2+
insoluble (will be a solid) because Pb
makes it insoluble
-
Example 2: Sr(NO
)
is soluble because NO
is always soluble.
3
2
3
+
2-
Example 3: K
O is soluble because K
is an alkali metal and is always soluble, but MgO is insoluble because O
is
2
+
2+
2+
2+
insoluble unless bonded to alkali metals or NH
in which it would be completely soluble, or bonded to Ca
, Sr
, or Ba
4
2+
in which it would be partially soluble. Therefore, CaO would be somewhat soluble because of Ca
.
+
2-
Example 4: (NH
)
CO
is soluble because of NH
, but CaCO
is insoluble because CO
is insoluble unless bonded to
4
2
3
4
3
3
+
alkali metals or NH
.
4
Example 5 (on your own): Will BaSO
be soluble? How about NaOH? How about HCl? How about AgCl? How about
3
Ba(OH)
? How about Mg(OH)
? How about MgF
? How about Ba(C
H
O
)
?
2
2
2
2
3
2
2
Answers: insoluble, soluble, soluble, insoluble, somewhat soluble, insoluble, insoluble, soluble
Strong Acids
Strong Bases
-
HNO
All alkali metals with OH
3
2+
2+
2+
-
HCl
Sr
Ba
or Ca
with OH
(ex: Sr(OH)
)
,
,
2
HClO
3
HIO
4
HClO
4
HBr
HI
H
SO
2
4
Note: All other acids and bases are weak!!
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