Net Ionic Equations And Solubility Rules
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1Review: forming ions
• Ionic (i.e. salt) refers to +ve ion plus -ve ion
• Usually this is a metal + non-metal or metal +
polyatomic ion (e.g. NaCl, NaClO
, Li
CO
)
3
2
3
• Polyatomic ions are listed on page 71
• (aq) means aqueous (dissolved in water)
• For salts (aq) means the salt exists as ions
+
–
• NaCl(aq) is the same as: Na
(aq) + Cl
(aq)
2–
S
3–
+
–
PO
• Acids form ions: HCl(aq) is H
(aq) + Cl
(aq),
+
Na
2+
4
2Ca
–
3Cl
+
–
Bases form ions: NaOH(aq) is Na
+ OH
3+
Al
Q - how is charge determined (+1, -1, +2, etc.)?
Net ionic equations
• F, Cl
electron, thus forming
and solubility rules
• Ca
electrons, thus forming
Practice with writing ions
Background: valences and formulas
Q - Write ions for Na
CO
(aq)
• Charge can also be found via the compound
2
3
+
• E.g. in NaNO
(aq) if you know Na forms Na
,
3
–
then NO
must be NO
(NaNO
is neutral)
3
3
3
• By knowing the valence of one element you
• Notice that when ions form from molecules,
can often determine the other valences
charge can be separated, but the total charge
Q - Write the ions that form from Al
(SO
)
(aq)?
(and number of each atom) stays constant.
2
4
3
Step 1 - look at the formula:
Al
(SO
)
(aq)
Q - Write ions for Ca
(PO
)
(aq) & Cd(NO
)
(aq)
2
4
3
3
4
2
3
2
3
2
Step 2 - determine valences:
Al
(SO
)
4
(Al is 3+ according to the periodic table)
3+
2–
Step 3 - write ions:
2Al
(aq) + 3SO
(aq)
Q - Write ions for Na
S(aq) and Mg
(BO
)
(aq)
4
2
3
3
2
• Note that there are 2 aluminums because Al
has a subscript of 2 in the original formula
Types of chemical equations
Equations must be balanced
Equations can be divided into 3 types (pg. 333)
• There are two conditions for molecular, ionic,
and net ionic equations
1) Molecular, 2) Ionic, 3) Net ionic
Materials balance
• Here is a typical molecular equation:
S(aq) → CdS(s) + 2NaNO
Both sides of an equation should have the
Cd(NO
)
(aq) + Na
(aq)
3
2
2
3
same number of each type of atom
• We can write this as an ionic equation (all
compounds that are (aq) are written as ions):
Electrical balance
2+
–
+
2–
Both sides of a reaction should have the same
Cd
(aq) + 2NO
(aq) + 2Na
(aq) + S
(aq)
3
→ CdS(s) + 2Na
+
–
net charge
(aq) + 2NO
(aq)
3
• To get the NET ionic equation we cancel out
Q- When NaOH(aq) and MgCl
(aq) are mixed,
2
all terms that appear on both sides:
_______(s) and NaCl(aq) are produced. Write
(aq) → CdS(s)
2+
2–
Net:
Cd
(aq) + S
balanced molecular, ionic & net ionic equations
Solubility
First write the skeleton equation
• Precipitation refers to the formation of a solid
2
NaOH(aq) + MgCl
(aq)
2
→ Mg(OH)
2
from ions. A precipitate is “insoluble”
(s) + NaCl(aq)
2
• Soluble and insoluble are general terms to
Next, balance the equation
Ionic equation:
describe how much of a solid dissolves.
+
-
2+
-
2Na
(aq) + 2OH
(aq) + Mg
(aq) + 2Cl
(aq)
• Solubility can be predicted from rules (pg.399)
→ Mg(OH)
+
-
(s) + 2Na
(aq) + 2Cl
(aq)
• These are general rules, based on observation
2
Net ionic equation:
• To determine solubility, follow the rules in order
(aq) → Mg(OH)
-
2+
2-
2OH
(aq) + Mg
(s)
• Note: in rule 4 that sulfate = SO
2
4
• You will not have to memorize these rules, you
Write balanced ionic and net ionic equations:
(aq) → CuCl
will have to use the rules to predict solubility
CuSO
(aq) + BaCl
(aq) + BaSO
(s)
4
2
2
4
(aq) + LiOH(aq) → ______(aq) + Fe(OH)
• Read over example 11.2 (pg. 400)
Fe(NO
)
(s)
3
3
3
(aq) → _________(s) + NaCl(aq)
Na
PO
(aq) + CaCl
• Do 11.26 (435) (list the relevant rule for each)
3
4
2
(aq) → ________(aq) + Ag
Na
S(aq) + AgC
H
O
S(s)
• Do PE 5 (pg. 400) and 11.28 (pg. 435)
2
2
3
2
2
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