lecture2 - Because of the difference in electronegativity...

Info iconThis preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
The Polar Nature of Water The Polar Nature of Water Because of the difference in electronegativity between oxygen (3.5) and hydrogen (2.1) and its shape, water is a polar molecule the net charge on oxygen is -0.66 and that on each hydrogen is +0.33 H H O δ + δ + δ - +0.33 +0.33 -0.66
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Electronegativity Electronegativity Electronegativity: Electronegativity: a measure of an atom’s attraction for electrons it shares in a chemical bond with another atom on Pauling’s scale, fluorine, the most electronegative element, is assigned a value of 4.0 H . 21 B . 20 C . 25 N . 30 O . 35 F . 40 Li . 10 Be . 15 Al . 15 Si . 18 P . 22 S . 26 Cl . 30 Na . 09 Mg . 12 A 1 A 2 A 3 A 4 A 5 A 6 A 7
Background image of page 2
Molecules such as CO 2 have polar bonds but because of their geometry, are non-polar molecules This is a linear molecule and the pull from each oxygen atom cancels out the other. Water is polar because of the differences in electronegativity AND its asymmetrical shape δ + δ - δ - O= C= O -0.21 +0.42 -0.21
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Solvent Properties of H Solvent Properties of H O O Ionic compounds (e.g.,KCl) and low-molecular- weight polar covalent compounds (e.g., C 2 H 5 OH and CH 3 COCH 3 ) tend to dissolve in water The underlying principle is electrostatic attraction of opposing charges (eg. the positive dipole of water for the negative dipole of another molecule). ion-dipole interaction: ion-dipole interaction: e.g., KCl dissolved in H 2 O ( ionic compounds and polar compounds ) dipole-dipole interactions: dipole-dipole interactions: e.g., ethanol or acetone dissolved in H O ( between polar molecules )
Background image of page 4
Bond Energies Bond Energies Covalent Type of  Bond Energy O-H H- H C-H Hydrogen bond (H 2 O) Ion-dipole bond Hydrophobic interaction van der Waals bond Non- covalent Example kJ•mol -1 kcal•mol -1 460 110 416 100 413 105 20 5 20 5 4-12 1-3 4 1 Table 2.3 Some Bond Energies
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Solvent Properties of H Solvent Properties of H 2 2 O O Hydrophilic: Hydrophilic: water-loving tends to dissolve in water Hydrophobic: Hydrophobic: water-fearing tends not to dissolve in water Amphipathic Amphipathic : : both hydrophobic and hydrophilic molecules that contain one or more hydrophobic and one or more hydrophilic regions, e.g., sodium palmitate
Background image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 26

lecture2 - Because of the difference in electronegativity...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online