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
Department of Chemistry and Biochemistry
CHM 101 - Reeves
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 - Reeves
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 - Reeves
CHM 101 – Chapter Four
Weak electrolyte
Strong electrolyte
++
++
-
Nonelectrolyte
+
-
++
-
-
++
-
Ca2+
Cl-
HF
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+
-
H+
F-
O2
CHM 101 - Reeves
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 - Reeves
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 - Reeves
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 - Reeves
CHM 101 – Chapter Four
Strong acids/bases are strong electrolytes that dissociate completely.
Weak acids/bases are weak electrolytes that dissociate only slightly.
Weak acid/base
Strong acid/base
hydrochloric acid (HCl)
+
-
hydroflouric acid (HF)
+
-
+
+
+
+
-
-
-
+
+
-
H+
Cl-
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HF
+
-
H+
F-
CHM 101 - Reeves
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 - Reeves
CHM 101 – Chapter Four
Concentration of Solutions
Suppose 1.0 moles of hydrochloric acid is dissolved in 500 ml of water.
0.1 moles H+
0.1 moles Cl-
We define the Molarity (M) of solute A in a solution as M A 
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moles of A
liter of solution
CHM 101 - Reeves
CHM 101 – Chapter Four
0.1 moles H+
0.1 moles Cl-
M H   M Cl   M HCl 
Suppose 200 mL were removed and placed in a separate flask.
200 mL
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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
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CHM 101 - Reeves