4ACH11_Part3_Phase Transitions and Diagrams

4ACH11_Part3_Phase Transitions and Diagrams - under which...

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12/5/2010 1 Phase Transitions Heating Curves Chapter 11 Phase Transitions: (s) (l) (l) (s) (l) (g) (g) (l) (s) (g) (g) (s) melting freezing vaporization condensation sublimation deposition D H fusion (kJ/mole) - H fus H vap - H vap H sub - H sub (= H dep )
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12/5/2010 2 When heat is added during a phase change, the temperature does not change. This can be seen using a “heating curve” for water. Starting at -20 ° C … 140 120 100 80 60 40 20 0 -20 T time Let’s calculate the total heat required to change 10.0 g of ice at -20 ° C to steam at 140 ° C. D H fus =6.01kJmol -1 , D H vap =40.7 kJmol -1 , Cp ice =37.7 J ° C -1 mol -1 , Cp liq =75.2 J ° C -1 mol -1 , Cp vap =33.6 J ° C -1 mol -1 140 120 100 80 60 40 20 0 -20 T time mol Cp ice D T q 1 = q 2 = mol D H fus q 3 = mol Cp liq D T q 4 =mol D H vap q 5 =mol Cp vap D T
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12/5/2010 3 H 2 0(s) H 2 0(s) -20 ° C 0 ° C H 2 0(s) H 2 0(l) 0 ° C 0 ° C H 2 0(l) H 2 0(l) 0 ° C 100 ° C H 2 0(l) H 2 0(g) 100 ° C 100 ° C H 2 0(g) H 2 0(g) 100 ° C 140 ° C q total = 31.3 kJ/mole q 1 = 0.419 kJ/mole q 2 = 3.34 kJ/mole q 3 = 4.18 kJ/mole q 4 = 22.6 kJ/mole q 5 = 0.746 kJ/mole A graphical way to summarize the conditions
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Unformatted text preview: under which the different states of a substance are stable is called a Phase Diagram 12/5/2010 4 Heres a phase diagram for water: P (atm) T( C) 1.0 (s) (l) (g) 100 Vaporization curve Sublimation curve Triple Point : 0.01 C, 0.00603 atm . All three phase coexist Critical Point : 374 C, 218 atm Point beyond which it is not possible to distinguish between liquid and vapor regardless of applied pressureplasma or supercritical fluid T c Melting curve P c Heres a phase diagram for carbon dioxide: P (atm) T( C) 1.0 (s) (l) (g) 100-78 12/5/2010 5 And heres a phase diagram for sulfur: P (atm) T( C) (s) (l) (g) 119 150 1290 1X10-5 6X10-5 (s) Rhombic Monoclinic 95 A B C...
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This note was uploaded on 01/17/2012 for the course CHEM 4A taught by Professor Apriladrian during the Spring '11 term at UC Merced.

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4ACH11_Part3_Phase Transitions and Diagrams - under which...

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