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.
28. A durene-biphenyl mixture that is 60% durene by mass at 90°C was slowly cooled to 20°C, then slowly heated to 70°C (all at 1 atm). Based on Figure 1, at the end of this procedure the mixture consisted of:
Your Answer is
Correct Answer is F
Explanation
Look directly at figure 1, when the abscissa is 60 and the ordinate is 70, the corresponding area is solution (l), so there is only solution at this time