Previously in Chem 104: unit cell, Z, at.wt related to density
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Transcript of Previously in Chem 104: unit cell, Z, at.wt related to density
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
The Basics of a Phase Diagram
Temperature, T
Pre
ssure
, P
solidliquid
gas
What does the slope of this linetell us?
Triple point: