# Predicting solubility by Ax2YAZF

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```									Predicting solubility
• Using the table of solubilities we can now
predict which of the products of a double
replacement reaction will be insoluble
(form solids or precipitates : have low
solubilities) and which will remain soluble.
Solubility of Ions

Negative ions         Positive ions                           Soluble
(anion)           +   (cation)                                Ie: > 0.1 mol/L

Any anion         +   Alkali metal ions                       Soluble
(Li+, Na+, K+,Rb+,or Cs+)

Any anion         +   Ammonium, NH4+                          Soluble
Nitrate NO3-      +   Any cation                              Soluble
Acetate CH3COO-   +   Any cation except Ag+                   soluble

Chloride Cl-      +   Ag+, Pb2+, Hg22+, or Cu+                Not soluble
Bromide Br-       +   Any other cation                        Soluble
Iodide I-         +
Sulfate,SO42-     +   Ca2+, Sr2+, Ba2+, Ra2+, Ag+, or Pb2+    Not soluble
+   Any other cation                        soluble

Sulfide, S2-      +   Alkali metals or NH4+                   Soluble
+   Be2+, Mg2+, Ca2+, Sr2+, Ba2+, or Ra2+   Soluble
+   Any other cation                        Not soluble
Hydroxide, OH-    +   Alkali metals or NH4+                   Soluble
+   Sr2+, Ba2+, or Ra2+                     Slightly soluble
+   Any other cation                        Not soluble
phosphate,PO43-   +   Alkali metals or NH4+                   Soluble
carbonate,CO32-   +   Any other cation                        Not soluble
Sulfite,SO32-
Pb(NO3)2(aq) + 2 KI(aq)  PbI2 (s) + 2KNO3(aq)

• overall ionic equation, which separates all
the ions out:
Pb2+(aq) + 2 NO3- (aq) + 2 K- (aq) + 2 I- (aq)
 PbI2 (s) + 2 K+ (aq) + 2 NO3- (aq)

Stays as a solid

Pb2+ (aq) + 2 I- (aq)  PbI2 (s)
• The NO3- ion and the K+ ion are called
spectator ions.
• Silver nitrate combines with potassium
iodide.
• a) Nonionic or double replacement
reaction
AgNO3 (aq)+KI (aq) → AgI (?)+KNO3 (?)
• Using the solubility table we see that
nitrates are soluble with all positive ions
and Iodide ion is insoluble with silver.
AgNO3 (aq)+KI (aq)→AgI (s)+KNO3 (aq)
• Now that we have predicted the solid that
will form we can proceed to write the net
ionic equation.
• Ag + (aq) + I- (aq) → AgI (s)
i) silver nitrate + potassium iodide
ii) ammonium sulfide + lead(II) nitrate
iii) zinc nitrate + sodium carbonate
Separating ions:
Pb 2+ (aq) ; Ba 2+ (aq) ; Cu 2+ (aq)

Ba2+ and Cu2+             PbCl2 ppt outs
soluble

CuS ppt out

Ba2+ soluble              Ba3 (PO4)2 ppt out
• Using the solubility table create a flow
chart that describes how to separate the
following ions, if they are dissolved
together in a solution. The last ion may
remain in solution.
•
a) Ag+ (aq) ; Ba2+ (aq) ; Mg2+ (aq)
• b) Ba2+ (aq) ; K+ (aq) ; Zn2+ (aq)
• c) Pb2+ (aq) ; Al3+ (aq) ; Sr2+ (aq)
• d) Sr2+ (aq) ; Mg2+ (aq) ; Fe3+ (aq)
1. Ionic Substances ( containing a metal or NH4-
ion )
• Ionic substances are composed of positive
and negative ions. Arrhenius proposed that
ionic substances come apart when they enter
a water solution, and the ions are free to
move about in the solution. The called this
process dissociation.
• CaCl2 (s) -------> Ca 2+ (aq) + 2 Cl- (aq)
• * Notice that the reactions are balanced for
charge and # of atoms.
2. Acids (containing nonmetals with hydrogen
written first in the formula)
• Certain molecular substances also form
mobile ions when placed in solution.
Arrhenius proposed that acids when placed in
solution form mobile ions. He called this
process ionization.
• H2 SO4 (l) -------> 2 H+ (aq) + SO4 2- (aq)
• In both cases (dissociation and ionization)
the end result is mobile ions in solution. Thus
since ions are present and can move, both
acids and ionic substances conduct electricity
in solution and are termed electrolytes.
3. Molecular (contain only nonmetals)
• Molecular substance that are not acids
on the other hand do not ionize nor
dissociation and do not form ions in
solution. Therefore these substances
are non-electrolytes.
• CO2 (g) ------> CO2 (aq)

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