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.
25. According to Figure 2, at 1 atm, solid will NOT be present in a durene-naphthalene mixture at 55°C that contains which of the following percents durene by mass?
Your Answer is
Correct Answer is B
Explanation
Look at figure 1. The l in the brackets in the figure represents liquid, and s represents solid. When the temperature on the ordinate is 55, the area where no solid appears corresponds to 30%-60% on the abscissa. It is safest to choose 50%