Previously in Chem 104:

• unit cell, Z, at.wt related to density

• types of closest packing, ccp= fcc, hcp

• Ionic Unit Cells for CsCl and NaCl

TODAY• QUIZ answer key out - send self-check by Tuesday 5PM

• Is Aluminum a stable solid?

•Born Haber Cycles

• “why doesn’t that solid exist”

• phase diagrams

Born Haber Cycles Relate Lattice Enthalpy and Heat of Formation

Hf Must be (-) for a stable solid

ionic solid

Elements inStandard States:M(s) , X2(g)

Energy

Born Haber Cycles

Hf must be (-) for a stable solid

ionic solid, MX

M(s) , X2(g)

Energy

M+(g) , X- (g)M+(g)

M(g)

X- (g)

X (g)

Hsub

HI.E.

HBD

Hlattice

HEA

Born Haber Cycles

ionic solid, MX

M(s) , X2(g)

Energy

M+(g) , X- (g)M+(g)

M(g)

X- (g)

X (g)

Hsub

HI.E.

HBD

Hlattice

HEA

Hf = Hsub + HI.E + HBD + HEA + Hlattice

Hf

Born Haber Cycles

ionic solid, NaCl

Na(s) , Cl2(g)

Energy

Na+(g) , Cl- (g)Na+(g)

Na(g)

Cl- (g)

Cl (g)

Hsub

HI.E.

HBD

Hlattice

HEA

Hf = Hsub + HI.E + HBD + HEA + Hlattice

Hf

For NaCl: -381 = +108 + 496 + 121 – 349 - 757

Hf = Hsub+ DHI.E + HBD + HEA + Hlattice

For NaCl: -381 = +108 + 496 + 121 – 349 - 757

For NaO: +2230 = +108 + 5058 + ½ (493) + 639 - 3820

Positive Hf: NaO does not (can not) exist!

For Al2O3:-2365 = 2(+150 + 5139) + 3/2 (493) + 3 (639) - 15,600

What factors affect the parameters in the Born-Haber calculations?

HEA: HI.E:

HBD:

Hsub:

Hlattice:

Hlattice ~ Ulattice = C NA { (Z+)(Z-) d

Solids and Phase Diagrams.

Temperature, T

Pre

ssure

, P

Energy

The Basics of a Phase Diagram

Temperature, T

Pre

ssure

, P

solidliquid

gas

What does the slope of this linetell us?

Triple point:

H2O Phase Diagram

Temperature, T

Pre

ssure

, P

solid

liquid

gas

CO2 Phase Diagram

Temperature, T

Pre

ssure

, P

solidliquid

gas

Fe-C (steel) Phase Diagram

(Fe3C)

Steel

(BCC)

FCC

FCC

Cast Iron