Passage V
A binary phase diagram (BPD) shows how the phases of a mixture of 2 chemicals vary with temperature and composition at 1 atmosphere (atm) of pressure. The phases include the solid (s) phase of each chemical and the liquid (I) solution phase of the 2 chemicals. The eutectic is the point where all 4 regions of the BPD intersect. It indicates the conditions at which all the phases represented in the 4 regions exist in equilibrium. When a mixture is at equilibrium, no net phase change occurs. Figure 1 is a BPD for durene and biphenyl. Figure 2 is a BPD for durene and naphthalene.
Figures adapted from Jurgen Gallus et al. , “Binary Solid-Liquid Phase Diagrams of Selected Organic Compounds."©2001 by Division of Chemical Education, Inc.,American Chemical Society.
29. Based on Figures 1 and 2, the melting point of durene is closest to which of the following?
Your Answer is
Correct Answer is D
Explanation
According to figure 1 and figure 2, when the abscissa percent durene by mass in mixture is 100, it means pure durene at this time.
Looking at the ordinate at this time, when the temperature is about 79°C, durene can be in a liquid state, so it is inferred that its melting point is about 79°C