### Example Problem Phase Equilibrium

Question:
Magnesium oxide and nickel oxide withstand high temperatures. However, they do melt when temperature is high enough and the behaviour of mixtures of the two is of considerable interest to the ceramics industry. Draw the temperature – composition diagram for the system using the data below, where x is the mole fraction of MgO in the solid and y is its mole fraction in the liquid.

q/oC                       1960                       2200                       2400                       2600                       2800
X                             0                              0.35                        0.60                        0.83                        1.00
Y                              0                              0.18                        0.38                        0.65                        1.00

State (a). the temperature at which a mixture with x = 0.3 begins to melt, (b). the composition and proportion of the phases present when a solid of composition  x = 0.3 is heated to 2200 oC, (c).  The temperature at which a liquid of composition y = 0.7 will begin to solidify.