Chem 161-2010 Lecture 23

Chem 161-2010 Lecture 23 - CHEMISTRY 161-2010 LECTURE 23...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
CHEMISTRY 161-2010 LECTURE 23 ATTENDANCE QUIZ RECITATION EXAM RECITATION QUIZ? Chem 161-2010 Lecture 23 1
Background image of page 1

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

View Full DocumentRight Arrow Icon
PLAN FOR TODAY : CHAPTER 11 (11.5 – 11.9) • INTERMOLECULAR FORCES (forces that attract one molecule to another) -- Electrostatic interaction (aka charge-charge/ ionic interaction) -- Hydrogen bonding -- Dipole-dipole interaction -- London forces Chem 161-2010 Lecture 23 2
Background image of page 2
Intermolecular forces: Forces between molecules; the forces that attract one molecule to another. “Inter”, Latin = between, e.g., intercollegiate athletics Up until now we studied intramolecular forces, e.g., C-C, N≡N; now we’ll discuss intermolecular forces, e.g., H 2 O. . . H 2 O e.g., intranet vs. internet; a net within a company vs. a net between all people of the world Chem 161-2010 Lecture 23 3 INTERMOLECULAR FORCES
Background image of page 3

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

View Full DocumentRight Arrow Icon
INTERMOLECULAR FORCES ET: Intramolecular bonds are much stronger than intermolecular bonds; e.g., H 2 (g) → 2H(g) BE=436 kJ/mol; H 2 (l) → H2( g ) ∆Hvapn = 0.90 kJ/mol ET: Only ideal gases don’t have intermolecular forces. ET: Discuss each force. Relative Strength * Electrostatic interaction (ion-ion interaction) 1000 = charge-charge interaction = ionic interaction Coulomb’s Law: F = k(Q 1 x Q 2 )/r 2 Hydrogen bonding 100 Y,Y’ = N, O or F Y ― H Y’ ET: Strong bond because very strong dipole-dipole interaction due to electron-naked small H getting close to small strongly electronegative atoms. F = k(Q 1 x Q 2 )/r 2 ; r is small, so force is large. Dipole-dipole interaction 10 London forces 1 Magnitude of London forces very sensitive to size/MW/surface area because the greater the size the easier the formation of dipoles (i.e., the greater the polarizability). Compare Xe to Ne. More electrons and electrons further from the nucleus make xenon more polarizable. Also, the greater the surface area, the more the contact. London forces used by all molecules, but force less important if other forces available. *Relative numbers made up. They are used simply to provide the concept. Chem 161-2010 Lecture 23 4
Background image of page 4
Electrostatic Attraction E = k(q 1 q 2 /r) Compound Lattice Energy (kJ/mol) NaF -910 CaO -3414 Chem 161-2010 Lecture 23 5
Background image of page 5

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

View Full DocumentRight Arrow Icon
HYDROGEN BONDING Chem 161-2010 Lecture 23 6
Background image of page 6
Chem 161-2010 Lecture 23 7
Background image of page 7

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

View Full DocumentRight Arrow Icon
HYDROGEN BONDING Boiling points of hydrogen halides Boiling points HF +20 HCl -85 HBr -67 HI -35 Notice that the HI, HBr, HCl boiling point trends follow the size effect: larger molecules having higher boiling points (stronger dispersion forces). Following this trend, we would predict HF to have a boiling point of about -100. The boiling point is +20 because of hydrogen bonding. Boiling points
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 11/02/2011 for the course GEN CHEM 162 at Rutgers.

Page1 / 26

Chem 161-2010 Lecture 23 - CHEMISTRY 161-2010 LECTURE 23...

This preview shows document pages 1 - 9. Sign up to view the full document.

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