CHM 101 Chapter Four

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CHM 101 Chapter Four

• Properties of Aqueous Solutions
• Precipitation Reactions
• Acid Base Reactions
• Concentrations of Solutions
• Solution Stoichiometry

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CHM 101 Chapter Four
Properties of Aqueous Solutions

• A solution is a homogenous mixture that consists
  of
• the solvent the component in the solution
  present in the largest amount. In aqueous
  solutions, water is the solvent.
• the solutes the other components in the
  solution

Electrolytes are solutes that, when dissolved in
water, cause the solution to conduct electricity
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CHM 101 Chapter Four

• A solution is a homogenous mixture that consists
  of
• the solvent the component in the solution
  present in the largest amount. In aqueous
  solutions, water is the solvent.
• the solutes the other components in the
  solution

Electrolytes are solutes that, when dissolved in
water, cause the solution to conduct electricity

• Strong electrolyte a compound that, when
  dissolved in water, dissociates completely into
  mobile ions that effect the conduction of
  electricity.
• Weak electrolyte a compound that, when
  dissolved in water, dissociates only slightly
  into mobile ions that effect the conduction of
  electricity.

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CHM 101 Chapter Four
Water solvates strong electrolytes by surrounding
cations with partially negative oxygen directed
inward, and surrounding anions with partially
positive hydrogens directed inwards.
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CHM 101 Chapter Four
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CHM 101 Chapter Four
When aqueous silver nitrate (AgNO3)is added to
aqueous sodium chloride (NaCl), a white solid
forms. This precipitate is silver chloride (AgCl)
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CHM 101 Chapter Four
The solubility rules provide guidelines for
deciding which compounds are soluble and which
are insoluble
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CHM 101 Chapter Four
The solubility rules provide guidelines for
deciding which compounds are soluble and which
are insoluble
Generally, you need to know that the following
ionic compounds are soluble
Use these rules and/or the Solubility Table to
predict the results of a metathesis reaction.
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CHM 101 Chapter Four
Metathesis Reactions
Reactions in which cations and anions appear to
exchange partners.
When aqueous lead (II) acetate is mixed with
aqueous sodium chloride, a metathesis reaction
occurs, forming an insoluble precipitate.
A more accurate way to depict this reaction is to
list the species actually present in aqueous
solution, the ions themselves
produces the net ionic equation
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CHM 101 Chapter Four
Acids are substances that produce hydrogen ions
(H) when dissolved in water.

• Because a hydrogen atom consists of one proton
  and one electron, a hydrogen ion is a proton.
• Thus, acids are often defined as proton donors
• There are seven common strong acids (Table 4.2)
  that must be memorized.

Bases are substances that consume hydrogen ions
(H) when dissolved in water.

• Bases often produce hydroxide ion when they
  dissolve in water.
• The most common strong bases are the metal
  hydroxides (eg. NaOH, Ca(OH)2, Al(OH)3, etc.)

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CHM 101 Chapter Four
Strong acids/bases are strong electrolytes that
dissociate completely.
Weak acids/bases are weak electrolytes that
dissociate only slightly.
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CHM 101 Chapter Four
Acid/Base Reactions
Reactions between strong acids and bases are
similar to metathesis rxns. One of the products
is water.
Consider the reaction of sulfuric acid with
potassium hydroxide.
Again the most accurate way to describe this
reaction is by considering the ions themselves
produces the net ionic equation
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CHM 101 Chapter Four
Concentration of Solutions
Suppose 1.0 moles of hydrochloric acid is
dissolved in 500 ml of water.
We define the Molarity (M) of solute A in a
solution as
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CHM 101 Chapter Four
Suppose 200 mL were removed and placed in a
separate flask.
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CHM 101 Chapter Four
Solution Concentrations
The concentration of a solution is independent of
the amount (intensive property) and can be used
to convert between volume and moles.
How many moles of HCl are in 50 mL of a 2.0 M
solution?
What volume of this solution would provide 0.36
moles of HCl?
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CHM 101 Chapter Four
If 25 mL of a 1.0 M solution of copper II sulfate
is transferred to a 250 mL volumetric flask and
the solution is diluted to volume with water,
what is the concentration of the new solution?
Moles of CuSO4
Molarity of soln
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CHM 101 Chapter Four
What volume of 0.56 M sulfuric acid solution must
be mixed with sufficient water to create 325 mL
of 0.15 M sulfuric acid?
Moles of H2SO4
Volume of soln
What volume of this new sulfuric acid solution is
needed to completely react 2.56 g of potassium
hydroxide?
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CHM 101 Chapter Four Supplement Measuring
Acidity The pH Scale

• In aqueous solution, the concentration of
  hydrogen ions H typically ranges form 1.0 M to
  1x10-14M
• To provide a convenient way to describe acidity,
  the pH scale was defined

• Because the scale involves a minus sign, acidic
  solutions, with high hydrogen ion concentrations,
  have low pH.
• Thus, the pH of a solution for which H 0.001
  M is