a. i. Define polymorphism and distinguish the two main types of polymorphism. ii. Write a short note on polymorphic transformations in the silica system. b. Using the Clausius - Clapeyron relationship, derive an expression for the pressure on the system (P) in terms of the temperature of the system for an evaporation phase equilibrium. [Take the heat of vaporization to be Hvap.] c. The following phases are known to exist in a system at constant pressure: Cordierite (2MgO2Al2O35SiO2) Mullite (3Al2O32SiO2) Forsterite ( 2MgOSiO2) Protoenstatite ( MgOSiO2) Periclase (MgO) i. What are the components of the system? ii. Could all of the above-listed phases coexist at equilibrium? Explain. 25 Marks