## Info

(a) When cooling along path (1), what phases appear when the temperature reaches T3?

(b) When cooling along path (2), determine:

i) The phase that appears when the temperature reaches T4.

ii) The compositions and proportions of the coexisting phases at a temperature half-way between T3 and T4 (numerical values required).

iii) The phases that coexist when the temperature reaches T3.

8.22 The phase diagram of the U-O system from U to UO2 is shown below. The composition axis is expressed as the oxygen-to-uranium ratio, O/U. When O/U < 2, the single-phase oxide is designated as UO2-x, where O/U = 2-x.

(a) identify the phases present in each of the numbered regions of the diagram

(b) what phases are present at point P? How many degrees of freedom at this point

(c) at point x in the diagram:

i) identify the phases present ii) If more than one phase, determine their relative amounts and compositions 8.23 The phase diagram below represents an A-B system in which the liquid solution is ideal but the solid is not. Calculate the activity coefficient of A on the solidus curve at 880oC. The heat of melting of pure A is 25 kJ/mole. *b

8.24 The vapor in equilibrium with a solid A-B alloy has the same composition as the solid. For xBS = 0.1, the total vapor pressure (pA + pB) is 0.04 atm. For the pure components at the same temperature, psatA = psatB = 0.03 atm.

(a) If the solid solution were ideal, what should be the total vapor pressure over the alloy?

(b) Assuming that the solid solution obeys Regular solution theory, derive the equation from which the interaction energy, r = Q/RT can be calculated. Use the observed total vapor pressure at xBS = 0.1 and solve the equation for r.

(a) Apply the phase-separation analysis of Sect. 8.4.2 with the excess enthalpy given by:

hex = QxAxB(1 - axB) instead of Equation (8.15). a is a constant.

(b) Determine Q and a for the n-hexane/nitrobenzene system by fitting the two-phase dome in Figure 8.6 to the results of part (a)

Chap. 9 Chemical thermodynamics

9.1 Chemical Reactions 1

9.1.1 Categories of reactions - stoichiometry 1

9.1.2 Equilibrium 2

9.2 Enthalpy change of a reaction 4

9.3 Entropy change of reaction - the entropy rule-of-thumb 6

9.4 Criterion of Chemical Equilibrium 8

9.5 Gas-Phase Reaction Equilibria 9

9.5.1 Effect of Pressure on Gas-Phase Chemical Equilibria 11

9.5.2 Effect of temperature on gas-phase chemical equilibria 11

9.6 Solving for the Equilibrium Composition 12

9.6.1 The element conservation method 12

9.6.2 The reaction progress variable method 14

9.7 Reactions in a flowing gas 15

9.8 Simultaneous Gas Phase Reactions 15

9.9 Reactions between Gases and Pure Condensed Phases 17

9.9.1 Implications of the phase rule 18

9.9.2 Stability diagrams 18

9.9.3 Oxygen isobars on a phase diagram 19

9.9.4 Reactive gas in contact with a reactive metal 20

9.10 Reactions involving solutions 22

9.9.1 Solution of a reactant species in an inert solvent 23

9.9.2 Reactions in solution with two reactive species 24

9.11 Thermochemical Databases 26

9.11.1 Standard Free Energy of Formation 26

9.11.2 Graphical Representation - Ellingham Diagrams 27

9.11.3 Analytic Representation 32

9.11.4.Tabular Representation 32

9.12 Dissolution of Gases in Metals 36

9.12.1 Dissociative dissolution and Sieverts' law 36

9.12.2 The zirconium-hydrogen phase diagram 38

9.13 Computational thermodynamics 40

9.13.1 Method of Lagrange multipliers 40

9.13.2 Water decomposition example 41

Problems 42 