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)
                Add Cl-


Ba2+ and Cu2+             PbCl2 ppt outs
soluble

  Add S2-


Add PO43-
                          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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