Transcript Slide 1

Solubility Guidelines for
Compounds in Aqueous Solutions
•
1)
2)
•
It is very important that you know these guidelines and
how to apply them in reactions.
Common inorganic acids and low-molecularweight organic acids are water soluble.
All common compounds of the Group IA metal
ions and the ammonium ion are water soluble.
Li+, Na+, K+, Rb+, Cs+, and NH4+
Aqueous Solutions: An
Introduction
3) Common nitrates, acetates, chlorates, and
perchlorates are water soluble.
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NO3-, CH3COO-, ClO3-, and ClO4-
4) Common chlorides are water soluble.
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•
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Exceptions – AgCl, Hg2Cl2, & PbCl2
Common bromides and iodides behave similarly to
chlorides.
Common fluorides are water soluble.
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Exceptions – MgF2, CaF2, SrF2, BaF2, and PbF2
Aqueous Solutions: An
Introduction
5) Common sulfates are water soluble.
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Exceptions – PbSO4, BaSO4, & HgSO4
Moderately soluble – CaSO4, SrSO4, & Ag2SO4
6) Common metal hydroxides are water
insoluble.
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•
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Exceptions – LiOH, NaOH, KOH, RbOH & CsOH
Common bromides and iodides behave similarly to
chlorides.
Common fluorides are water soluble.
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Exceptions – MgF2, CaF2, SrF2, BaF2, and PbF2
Aqueous Solutions: An
Introduction
7) Common carbonates, phosphates, and
arsenates are water insoluble.
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CO32-, PO43-, & AsO43-
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Exceptions- IA metals and NH4+ plus Ca to Ba
Moderately soluble – MgCO3
8) Common sulfides are water insoluble.
• Exceptions – IA metals and NH4+ plus IIA metals
Ionic Equations

1.
There are three ways to write reactions in
aqueous solutions.
Molecular equation
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Show all reactants & products in molecular or ionic form
Zn(s) + CuSO 4(aq)  ZnSO4(aq) + Cu (s)
2.
Total ionic equation
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Show the ions and molecules as they exist in solution
Zn(s) + Cu
2
aq
+ SO
24aq
2
aq
 Zn
+ SO
24aq
+ Cu (s)
Ionic Equations
3.

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Net ionic equation
Shows ions that participate in reaction and removes
spectator ions.
Spectator ions do not participate in the
reaction. Spectator ions in < >’s.
Zn (s) + Cu 2aq  + SO 24-aq   Zn 2aq  + SO 24-aq  + Cu (s)
Zn(s) + Cu
2
aq
2
aq
 Zn
+ Cu (s)
Molecular
2 HCl(aq)
Total
1
aq 
2H
equation
+ Na2SO 3(aq)  2 NaCl(aq) + H2O   SO 2g 
ionic reaction
 2 Cl
1aq 
1
aq 
+ 2 Na
1
aq 
 SO
23aq 
2 Na  2 Cl
Net ionic reaction
1aq 

+ H 2O   SO 2g 
•Molecular equation
Ca(OH)2(aq) + 2 HNO3(aq)  Ca(NO3 )2(aq) + 2 H2O()
Total
ionic equation
Ca 2aq  + 2 OH-aq + 2 Haq + 2 NO3- aq  Ca 2aq  + 2 NO3- aq + 2 H2O()
Net
ionic equation
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2 OHaq  + 2 H

aq 
 2 H 2O( )
or bet t er
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OHaq  + H

aq 
 H 2O( )
•Molecular equation
Ca(NO3 )2(aq) + K2CO3(aq)  2 KNO3(aq) + CaCO3(s)
Total
Ca
2
aq 
ionic reaction
 2 NO
3aq 
2K
2K


aq 

aq 
 CO
23aq 

 2 NO
3aq 
Net ionic reaction
Ca
2
aq 
+ CO
23aq 
 CaCO3(s)
 CaCO3s 
•Molecular equation
3 CaCl2(aq) + 2 Na3PO4(aq)  6 NaCl(aq) + Ca3 PO4 2(s)
Total
ionic reaction
1
33 Ca 2aq   6 Cl1aq
+
6
Na

2
PO

aq 
4 aq  
1
aq 
6 Na

 6 Cl
1aq 
+ Ca 3 PO4 2s 
Net ionic reaction
3 Ca
2
aq
 2 PO
34aq 
 Ca3 PO4 2s 
Oxidation Numbers

Guidelines for assigning oxidation numbers.
1.
The oxidation number of any free, uncombined element
is zero.
The oxidation number of an element in a simple
(monatomic) ion is the charge on the ion.
In the formula for any compound, the sum of the
oxidation numbers of all elements in the compound is
zero.
In a polyatomic ion, the sum of the oxidation numbers of
the constituent elements is equal to the charge on the
ion.
2.
3.
4.
Oxidation Numbers
5.
6.
7.
Fluorine has an oxidation number of –1 in its
compounds.
Hydrogen, H, has an oxidation number of +1 unless it is
combined with metals, where it has the oxidation
number -1.
• Examples – LiH, BaH2
Oxygen usually has the oxidation number -2.
• Exceptions:
• In peroxides O has oxidation number of –1.
• Examples - H2O2, CaO2, Na2O2
• In OF2: O has oxidation number of +2.
Oxidation Numbers
8.
Use the periodic table to help with assigning
oxidation numbers of other elements.
a.
b.
c.
d.
e.
IA metals have oxidation numbers of +1.
IIA metals have oxidation numbers of +2.
IIIA metals have oxidation numbers of +3.
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There are a few rare exceptions.
VA elements have oxidation numbers of –3 in binary
compounds with H, metals or NH4+.
VIA elements below O have oxidation numbers of –2 in
binary compounds with H, metals or NH4+.
Assign oxidation numbers to the element
specified in each group of compounds

N in NaNO3

Sn in K2Sn(OH)6

P in H3PO4

S in SO32-

Cr in Cr2O72-
Assign oxidation numbers to the element
specified in each group of compounds
• N in NH3
• O in Na2O2
• Fe
• N in N2O4
Assign oxidation numbers to the element
specified in each group of compounds
• P in H4P2O7
• Hg in Hg2Cl2
• Li in LiH
• S in S4O62-