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									General Chemistry
            2011-2012
   First year Geology students



    Teacher of the course: Dler Mohammad Salh Sharef
                   M.Sc. in chemistry
              Email: dler.salh@univsul.net             1
  General
properties of
  aqueous
 solutions
                2
     AQUEOUS SOLUTIONS
   In Chemistry, many reactions take place in water.
    This is also true for Biological processes.

   Reactions that take place in water are said to
    occur in an aqueous solution.

   Three types of reactions take place in aqueous
    solutions: Precipitation, Acid-Base and Redox.
PROPERITIES OF AQUEOUS SOLUTIONS

 Solution-   a homogeneous mixture of two or
  more substances.
 Solute- a substance in a solution that is present
  in the smallest amount.
 Solvent- a substance in a solution that is
  present in the largest amount.

 Inan aqueous solution, the solute is a liquid or
 solid and the solvent is always water.
                                                 4
PROPERTIES OF AQUEOUS SOLUTIONS
   All solutes that dissolve in water fit into one of two
    categories: electrolyte or non-electrolyte.

   Electrolyte- a substance that when dissolved in water
    conducts electricity

   Non-electrolyte- a substance that when dissolved in
    water does not conduct electricity.

   To have an electrolyte, ions must be present in water.
      Compounds in Aqueous Solution
Ionic Compounds in Water (Electrolytes)
        The conductivity of the solution is due to the formation
of ions when the compound dissolves in water


            NaCl ( s ) H Na  (aq)  Cl  (aq)
                        2O




       These ions are not the result of a chemical reaction, they
are the result of a dissociation of the molecule into ions that
compose the solid.
                                                               6
    Compounds in Aqueous Solution
Ionic Compounds in Water
     Compounds in Aqueous Solution
        Molecular Compounds in Water
              (Non electrolytes)

       In this case no ions are formed, the molecules
just disperse throughout the solvent.

                      
          sugar( s )   sugar( aq)
                        H 2O
     Compounds in Aqueous Solution
        Molecular Compounds in Water
              (Non electrolytes)

      There are exceptions to this, some molecules are
strongly attracted to water and will react with it.
                                          
                      
          NH 3  H 2O  NH  OH   4



                                          
                      H 3O  Cl
          HCl  H 2O 
ELECTROLYTIC PROPERTIES OF
    AQUEOUS SOLUTIONS
  ELECTROLYTIC PROPERTIES OF
      AQUEOUS SOLUTIONS




STRONG VS. WEAK ELECTROLYTES
HOW DO YOU KNOW WHEN AN ELECTROLYTE IS STRONG OR WEAK?
         STRONG ELECTROLYTES
Produce many ions in aqueous solution an conduct
 electricity well.

The most common strong electrolytes are soluble
 salts, strong acids and strong bases.

Acids are substances that produce H+ ion when they
 dissolve in water.
HCl, HNO3 and H2SO4 are common strong acids
      HNO3(aq) ----> H+(aq) + NO3-(aq)
NaOH and KOH are a common stong bases:
      NaOH(s) ----> Na+(aq) + OH-(aq)

All of the above species are ionized nearly 100%
           WEAK ELECTROLYTES
Produce relatively few ions in aqueous solution

The most common weak electrolytes are weak acids
 and weak bases.

Acetic acid is a typical weak acid:
       HC2H3O2(aq) ----> H+(aq) + C2H3O2- (aq)

Ammonia is a common weak base:
    NH3(aq) + H2O(l) -----> NH4+(aq) + OH- (aq)

Both of these species are ionized only 1%
            NONELECTROLYTES

Dissolve in water but produce no ions in solution.


Nonelectrolytes do not conduct electricity because
 they dissolve as whole molecules, not ions.

Common nonelectrolytes include ethanol and table
 sugar (sucrose, C12H22O11)
ELECTROLYTIC SOLUTIONS
Precipitation
  Reactions
                16
          PRECIPITATION REACTIONS
 Precipitation Reaction- a reaction that results in
  the formation of an insoluble product.
 These reactions usually involve ionic compounds.

 Formation of PbI2:
       Pb(NO3)2(aq) + 2KI(aq) →   PbI2(s) + 2KNO3(aq)
PRECIPITATE
        PRECIPITATION REACTIONS
   How do you know whether or not a precipitate
    will form when a compound is added to a
    solution?

   By knowing the solubility of the solute!

   Solubility- The maximum amount of solute that
    will dissolve in a given quantity of solvent at a
    specific temperature.

   Three levels of solubility: Soluble, slightly soluble
    or insoluble.
            Precipitation Reaction

- A reaction which forms a solid (precipitate)

  AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)

- AgCl is classified as an insoluble substance
             Precipitation Reaction
Net Ionic Equation
      AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)

- AgNO3 and NaNO3 are electrolytes in solution so they actually
  occur as free ions.

 Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) 
                             AgCl(s) + Na+(aq) + NO3-(aq)
            Precipitation Reaction
Net Ionic Equation
Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) 
                          AgCl(s) + Na+(aq) + NO3-(aq)

- Notice that NO3-(aq) and Na+(aq) occur in both the left
  and right side of the equation.

   -These are called spectator ions.
             Precipitation Reaction
Net Ionic Equation

      Ag+(aq) + Cl-(aq) AgCl(s)

- With the spectator ions removed, the resulting
  equation shows only the ions involved in the reaction
  remain.

- This is a net ionic equation.
 COMPOUNDS IN AQUEOUS SOLUTION
Solubility Guidelines for Ionic Compounds
1. Most nitrates (NO3-) and acetates (CH3CO2-) are
   soluble in water.
2. All chlorides are soluble except: Hg+, Ag+, Pb2+, Cu+
3. All sulfates are soluble except: Sr2+, Ba2+, Pb2+
4. Carbonates (CO32-), Phosphates (PO43-), Borates
   (BO33-),Arsenates (AsO43-), and Arsenites (AsO33-)
   are insoluble.
5. Hydroxides (OH-) of group Ia and Ba2+ and Sr2+ are
   soluble.
6. Most sulfides (S2-) are insoluble.
PRECIPITATION REACTIONS
 COMPOUNDS IN AQUEOUS SOLUTION
Solubility Guidelines for Ionic Compounds
Predict the solubility of the following compounds:

              PbSO4

              AgCH3CO2

              (NH4)3PO4

              KClO4
 COMPOUNDS IN AQUEOUS SOLUTION
Solubility Guidelines for Ionic Compounds
Predict the solubility of the following compounds:

              PbSO4                Insoluble

              AgCH3CO2

              (NH4)3PO4

              KClO4
 COMPOUNDS IN AQUEOUS SOLUTION
Solubility Guidelines for Ionic Compounds
Predict the solubility of the following compounds:

              PbSO4                Insoluble

              AgCH3CO2             Soluble

              (NH4)3PO4

              KClO4
 COMPOUNDS IN AQUEOUS SOLUTION
Solubility Guidelines for Ionic Compounds
Predict the solubility of the following compounds:

              PbSO4                Insoluble

              AgCH3CO2             Soluble

              (NH4)3PO4            Soluble

              KClO4
 COMPOUNDS IN AQUEOUS SOLUTION
Solubility Guidelines for Ionic Compounds
Predict the solubility of the following compounds:

              PbSO4                Insoluble

              AgCH3CO2             Soluble

              (NH4)3PO4            Soluble

              KClO4                Soluble

								
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