731 TABLE 21.5 Equilibrium data for methanol-water 0.1 0.2 0.3 0.4 0.5 0.417 0.579 0.669 0.729 0.780 0.6 0.825 0.7 0.8 0.871 0.915 0.9 0.959 1.0 1.0 21.2. A plant must distill a mixture containing 75 mol % methanol and 25 percent water. The overhead product is to contain 99.99 mol % methanol and the bottom product 0.002 mol %. The feed is cold, and for each mole of feed 0.15 mol of vapor is con- densed at the feed plate. The reflux ratio at the top of the column is 1.4, and the reflux is at its bubble point. Calculate (a) the minimum number of plates; (b) the minimum reflux ratio; (c) the number of plates using a total condenser and a reboiler, assuming an average Murphree plate efficiency of 72 percent; (d) the number of plates using a reboiler and a partial condenser operating with the reflux in equilibrium with the vapor going to a final condenser. Equilibrium data are given in Table 21.5