20 b week iii chapters 10 and 11
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• Chapter 10, 11( except 11.4 and and 11.6 -7) • Intermolecular potentials. Dipole – Dipole, Hydrogen bonding and ion-dipole, ion-ion • Co-existence Curves, Triple point, Critical point

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20 b week iii chapters 10 and 11

Chapter 10, 11( except 11.4 and and 11.6 -7)

• Intermolecular potentials.

Dipole – Dipole, Hydrogen bonding and ion-dipole, ion-ion

• Co-existence Curves, Triple point, Critical point

• Solutions. Interactions in solution, Boiling Point Elevation, Freezing Point Depression and Osmotic Pressure, Electrolyte solutions

Midterm next Friday:

Chaps 9(no 9.7), 10, 11.-11.3

One side of page notes, closed book

Review Session Wednesday

20 B Week III Chapters 10 and 11


H2O P-T Phase Diagram

PE

PE+KE

KE


Pressure -Volume Phase Diagram

SO2(g)SO2( l) SO2(s)

Shows the deviation from Ideal Gas behavior

The Real gas behavior is described well by the vdW’s Equation

Fig. 10-18, p. 461


P

NP

NP

NP

P

NP

NP

P

NP

P

P

H-bonds

VDW

Bond dipole

VDW

dipole-dipole

Bond dipole

VDW

dipole-dipole

VDW

dipole-dipole

H-bonds

P=[nRT/(V– nb)] – [a(n/V)2] n=N/NA and R=Nak

Notice the difference between polar molecules (dipole moment ≠0)

and non-polar molecules (no net dipole moment =0) CO2 and CH4


-e

+e

Electro-negativity of atoms

Dipole moment =eRe

A measure of the charge separation

In a molecule the more Electronegative atom in a bond will

transfer electron density from the less Electronegative atom

This forms dipole along the bond


-e

Dipole-Dipole interaction

+e

Strongest of the physical bonds

Except for hydrogen bonds

Which are the strongest of the

Physical bonds, e.g., (H2O)2

dimer

Dipole moment =eRe


vdW’s bonds versus dipolar bonds

R (Inter nuclear distance)

Between the centers of mass


Chemical bonds versus Physical bonds

R (Inter nuclear distance)

Between the centers of mass


Minimum Potential Structure of the Dimer: bond angles and bond lengths

How did we find this structure in

20A?

Which equation did we solve and

What approximation allowed us to

find this structure for

chemical bonds

Recall that these are physical bonds

and not chemical (electronic) bonds

rr

R (Internuclear distance)

Between the centers of mass

R-relative center of mass (cm) positions of the HCl monomers in (HCl) Dimer

cm= average mass positions along bond in the HCl monomers.

Re

m1

m2

r1

r2

cm

r2=(m2/m)Re and r1= (m1/m) Re

m=m1 + m2


- bond lengthse

+e

Dipole moment =eRe

A measure of the charge separation and therefore 


- bond lengthse

+e

Electro-negativity of atoms

Dipole moment =eRe

A measure of the charge separation

In a molecule the more Electronegative atom in a bond will

transfer electron density from the less Electronegative atom

This forms dipole along the bond


-e

+e


Chemical bonds bond lengthsversus Physical bonds

Physical bonds

Uses

Van der Waals Eq

Chemical bonds

Do not use

Van der Waal’s Eq

Why?


P bond lengths

NP

NP

NP

P

NP

NP

P

NP

P

P

H-bonds

VDW

Bond dipole

VDW

dipole-dipole

Bond dipole

VDW

dipole-dipole

VDW

dipole-dipole

H-bonds

P=[nRT/(V– nb)] – [a(n/V)2] n=N/NA and R=Nak

Notice the difference between polar molecules (dipole moment ≠0)

and non-polar molecules (no net dipole moment =0) CO2 and CH4


Boiling points bond lengths

Or Ze

Fig. 10-12, p. 456


H bond lengths2O P-T Phase Diagram

PE

PE+KE

KE


Density of H bond lengths2O vs Temperature

Fig. 10-15, p. 458


H bond lengths2O(l)

Density of H2O vs Temperature

H2O(s)

Fig. 10-15, p. 458


H bond lengths2O P-T Phase Diagram

PE

PE+KE

KE


Rate of evaporation vs time as the bond lengths

vapor pressure approaches Equilibrium

Where it equals the condensation Rate

H2O(l)  H2O(g)

Evaporation

All the Macroscopic

Properties, P, V, and T

are only defined at

Equilibrium.

Which means PV=nRT

and the vdW Eq. can

only be use under

Equilibrium conditions

Fig. 10-16, p. 459


H bond lengths2O P-T Phase Diagram

PE

PE+KE

KE


H bond lengths2O P-T Phase Diagram

Equilibrium Vapor Pressure

Super heated

H2O liquid

Will spontaneously

vaporize

Super cooled

H2O liquid will

Spontaneously freeze

In both spontaneous processes

the system will go to the Equilibrium

StatePhase and Pressure

Table 10-3, p. 460


Equilibrium Vapor Pressure vs Temperature bond lengths

Fig. 10-17, p. 460


In Solutions, for example when bond lengthsNaCl(s) is dissolved in H2O(l).

+ H2O

NaCl(s) + H2O(l) Na+(aq) +Cl-(aq)

(aq) means an aqueous solution, where water is the solvent,

major component.

The solute is NaCl, which is dissolved, minor component

Water molecules solvates the ions the

Cation (Na+) and the Anion (Cl-).

Fig. 10-6, p. 450


+∂ bond lengths

-2∂

-2∂

+

-2∂

Solvated Na+

-2∂

+∂

+∂

Fig. 10-6a, p. 450


Fig. 11-3, p. 480 bond lengths


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