Unit 2: Solutions

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Solutions
PART II Solvation and Polarity
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What actually happens in a solution?

• Solvation the process of dissolving
• NOT a chemical Rxn
• The reasons why a solute may or may not dissolve
  in a solvent are related to forces of attraction
  between solute and solvent particles

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Like dissolves like
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Review Polarity of Molecules

• Polar Molecules are molecules which have an
  uneven distribution of charge. One side of the
  molecule is negative while one side of the
  molecule is slightly positive. 
• Non-polar molecules are molecules in which there
  is no net separation of charge.

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Two steps in determining the polarity of a
molecule 

• Step 1 Determine the type of bonds (polar or
  non-polar) making up the molecule. 
• Step 2 If the molecule contains polar bonds,
  determine if there is a net separation of charge
  by looking at the shape of the molecule.
• Polar bonds does NOT necessarily equal a polar
  molecule!!!!!

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Review Determining Bond Type

• Bond types are determined by taking the
  difference in electronegativities between the
  bonded atoms
• Ionic Bonding
• - electronegativity difference of 1.7 or
  greater
• ?Polar Covalent Bond
• - electronegativity difference of 0.3 to 1.7
• ?Non Polar Covalent Bond
• - electronegativity difference of 0.0 to 0.3

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Review
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Electrolyte vs Non-electrolytes

• The solvation of an ionic material into water
  results in a electrolytic solution
• The ions of the solute will separate in water to
  permit the solution to carry an electric current

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Non- Electrolyte
Not ionized in water
Weak Electrolyte
Incompletely ionized in water
Completely ionized in water
Strong Electrolyte
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Try it

• Polarity WS