HOMOGENOUS AQUEOUS SOLUTIONS

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HOMOGENOUS AQUEOUS SOLUTIONS

• CHAPTER 15.2

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OBJECTIVE

• I will be able to explain the solution process

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SOLVENTS AND SOLUTES

• Aqueous solution water that contains dissolved
  substances
• Solvent dissolving medium
• Solute dissolved particles

Solvent dissolves the solute, which leaves the
solute dispersed in the solvent
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SOLVENTS AND SOLUTES

• Solvents and solutes may be solids, liquids, or
  gases
• Solutions are homogenous
• Particles are so small that solutions cant be
  filtered
• Most onic compounds and polar covalent molecules
  can dissolve in water
• Some exceptions include barium sulfate and
  calcium carbonate
• Non-polar molecules dont dissolve in water
• Methane, oil, grease, gasoline
• Oil and grease dissolve in gasoline

Like dissolves Like
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THE SOLUTION PROCESS

• Solvation process by which ions of an ionic
  solid become surrounded by solvent molecules
• When a solute (crystals of sodium chloride) is
  placed in water (polar covalent solvent), the
  partially charged oxygen and hydrogen atoms
  attract the ions of the solute
• Individual ions break away from crystal

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ELECTROLYTES AND NONELECTROLYTES

• Electrolyte compound that conducts an electric
  current when it is in an aqueous solution or in
  the molten state
• All ionic compounds are electrolytes because they
  dissociate ions
• Ions must be mobile to conduct electricity

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ELECTROLYTES AND NONELECTROLYTES

• Nonelectrolyte a compound that does not conduct
  an electric current when it is in an aqueous
  solution or in the molten state
• Many molecular compounds are nonelectrolytes
  because they arent composed of ions
• Butif a molecular compound dissolves in water,
  it can then become an electrolyte

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ELECTROLYTES AND NONELECTROLYTES

• Electrolytes conduct electric current at
  different degrees
• Strong electrolytes
• Soluble salts
• Inorganic acids
• Inorganic bases
• Weak electrolytes conduct electricity but
  poorly because only some of the solute in
  solution exists as ions
• HgCl2
• Ammonia (NH3)
• Organic acids
• Organic bases

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HYDRATES
Copper(II) sulfate pentahydrate CuSO45H2O

• Hydrates are compounds that contain water
• When an aqueous solution evaporates, the water
  molecules are part of the crystal structure
• Water in crystal is called water of
  crystallization or water of hydration

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HYDRATES

• Naming Hydrates
• Use appropriate prefix, depending on the number
  of water molecules
• Penta-, tri-, octa-

Compound IUPAC Name
CuSO45H2O Copper(II) sulfate pentahydrate
Na2SO410H2O
MgSO47H2O
CaSO42H2O
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HYDRATES
Sample Problem 15.1

• Calculating H2O in a Hydrate
• Calculate the percent by mass of water in washing
  soda, sodium carbonate decahydrate (Na2CO310H2O).

Percent water mass of water
mass of hydrate
x 100