PART II: Solvation and Polarity

2 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

3 “Like dissolves like”

4 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.

5 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!!!!!

6 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

7 Review:

8 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

9 Strong Electrolyte Non- Electrolyte Completely ionized in water - + salt - + sugar Not ionized in water - + acetic acid Weak Electrolyte Incompletely ionized in water

10 Try it: Polarity WS