PROBLEMS 2.1 The Fe-FeS phase diagram indicates that Fe and Fes are companies miscible in the liquid state and are completely immiscible in the solid stee The liquidus composition at 1200C is 37.4 mole percent Fe and 61 mole percent Fes. The heat of fusion of iron at its melting temperatures 1535C is 3670 calories/mole, and liquid iron has a heat capacity whidi 0.3 calories/degree-mole higher than the heat capacity of solid iron. a. Derive an expression for the free energy of fusion of iron, AG function of temperature. b. Calculate the activity of iron in a liquid solution of Fe and Fest which XFe = 0.374 at 1200C. C. Assume that the liquid Fe-FeS system is regular, and calculate the activity of iron in the liquid alloy in which XFe = 0.374 at 1535C. d. Calculate the excess free energy of mixing of the solution in which Xfe- 0.374 at 1535C. 3 =