POLARITY AND POLARITY AND SOLUBILITY:SOLUBILITY:

““Like dissolves like”Like dissolves like”

1.a) Review of shapes:1.a) Review of shapes:What are the five basic shapes?What are the five basic shapes?

LinearLinearTrigonal PlanarTrigonal PlanarTetrahedralTetrahedralTrigonal PyramidalTrigonal PyramidalBentBent

1.b) Review of Bonding:1.b) Review of Bonding:Ionic or covalent?Ionic or covalent?

Ionic = Ionic = metal + nonmetalmetal + nonmetalCovalent = Covalent = nonmetal + nonmetal +

nonmetalnonmetalNonpolar Covalent = Nonpolar Covalent = electrons electrons

shared equallyshared equallyPolar Covalent = Polar Covalent = electrons electrons

shared unequallyshared unequally

2. Definitions of Polarity2. Definitions of Polaritya)Polar bond—a)Polar bond—

bond involves unequal distribution bond involves unequal distribution of electronsof electrons

b)Polar molecule—b)Polar molecule— the molecule has an unequal the molecule has an unequal

distribution of electronsdistribution of electronsc)Dipole—c)Dipole—charges in a molecule charges in a molecule

are separated; use andare separated; use and

3. To determine if a molecule is 3. To determine if a molecule is polar you must know its shape!polar you must know its shape!

Draw Draw Lewis Structure & Bar Lewis Structure & Bar DiagramDiagram; Use and to ; Use and to show show charge distributioncharge distribution

Determine Determine ShapeShape of Molecule of MoleculeDetermine Determine PolarityPolarity of Molecule of Molecule

a) Ha) H22OO1) Lewis & Bar?1) Lewis & Bar?

2) Shape?2) Shape?3) Polarity?3) Polarity?

O H H

O—H H

bentPolar—electrons distributed unequally

b) OFb) OF22

1) Lewis & Bar?1) Lewis & Bar?

2) Shape?2) Shape?3) Polarity?3) Polarity?

O—F

bentNonpolar—electrons distributed equally

O F F F

b) CFb) CF44

1) Lewis & Bar?1) Lewis & Bar?

2) Shape?2) Shape?3) Polarity?3) Polarity?

tetrahedral

Nonpolar—electrons distributed equally

F C F F

F F—C—F F

F

4. Determining solubility:4. Determining solubility:““Like Dissolves LikeLike Dissolves Like””

Polar compoundsPolar compounds like water like water dissolve polar and ionicdissolve polar and ionic solids solids like NaCl like NaCl

Nonpolar compoundsNonpolar compounds like oils like oils and fats and fats dissolve other dissolve other nonpolar nonpolar compoundscompounds

5. Like Dissolves Like:5. Like Dissolves Like:Why is this important?Why is this important?

Many pesticides and other Many pesticides and other dangerous toxins are dangerous toxins are nonpolarnonpolar and therefore and therefore fat solublefat soluble

These These nonpolar nonpolar substancessubstances build up in the fat reservesbuild up in the fat reserves of of animals, causing harmanimals, causing harm

DDT in eaglesDDT in eagles; ; PCB’s in PCB’s in humanshumans

Determining Solubility Examples:Determining Solubility Examples:6. a) Are these pairs soluble?6. a) Are these pairs soluble?

HCl HCl HH22OO

Both are polar, therefore they Both are polar, therefore they are solubleare soluble

O—H

HH—Cl

Determining Solubility Examples:Determining Solubility Examples:6. b) Are these pairs soluble?6. b) Are these pairs soluble?

CFCF44 NHNH33

CFCF44 is nonpolar, NH is nonpolar, NH33 is polar; is polar;

therefore NOT SOLUBLEtherefore NOT SOLUBLE

F—C—F F

F H—N—H H

7. Practical Application:7. Practical Application:ChromatographyChromatography

Pens can be identified using Pens can be identified using chromatographychromatography

Pen ink is a Pen ink is a mixturemixture which can which can be separated using various be separated using various solventssolvents

A A chromatogram chromatogram (“color (“color picture”) results from the picture”) results from the process of chromatographyprocess of chromatography