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8.11 Phase Diagrams with Intermediate Phases and Compounds. Terminal phase: a solid solution of one component in another for which one boundary of the phase field is a pure component. Intermediate phase: a phase whose composition range is between those of terminal phases.
Phase diagrams are a road map to understand the conditions for phase formation or transformation in any material system. One can use phase diagrams as the starting point for materials design and process optimization. One state point (103 bar, 1000 marked by a crosshair. Figures: JPEDAV (2014) 35:735–760.
Phase diagram is a graphical representation of all the equilibrium phases as a function of temperature, pressure, and composition. For one component systems, the equilibrium state of the system is defined by two independent parameters (P and T), (T and V), or (P and V). Pressure-temperature phase diagram for H2O:
• Many different types of phase transitions, e.g. solid-liquid; conducting-superconducting; solid-solid • Can use chemical potential to classify phase transitions into different types using the so-called Ehrenfest Classification • Phase changes are often accompanied by changes of H and V. These changes cause abrupt
1. Write down the reactions that correspond to the enthalpies of formation of (a) CH 4 (g) and (b) H 2 O(l). (a) (b) 2. Why are Δ f H° (O 2(g)) and Δ f H° (H 2 (g)) both equal to 0 kJ? (Hint: what is the reaction in each case?) Model 2: Calculating the Enthalpy of Reaction using Δ f H
The reaction occurring in a phase diagram can be determined by identifying the invariant reaction line and finding the 'outside' and inside phases. The outside phases go to form the inside phase. From this, the form of the reaction can be written.
A reaction equation is an algebraic equation that is solely a function of the properties of the reacting materials and reaction conditions (e.g. species concentration, temperature, pressure, or type of catalyst) at any point in the system.
