eutectic - Home-work#7 due Friday November 5 2010 W.D...

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Home-work #7 due Friday, November 5, 2010. W.D. Callister, Jr Materials Science and Engineering, 8-th Edition Problems: 9.1; 9.6; 9.9; 9.12; 9.16; 9.32; 9.36; 9.39;9.40; 9.44; 9.49; 9.53; 9.64;9.65 9.1 Consider the sugar–water phase diagram of Figure 9.1. (a) How much sugar will dissolve in 1500 g water at 90 C (194 F)? (b) If the saturated liquid solution in part (a) is cooled to 20 C (68 F), some of the sugar will precipitate out as a solid. What will be the composition of the saturated liquid solution (in wt% sugar) at 20 C? (c) How much of the solid sugar will come out of solution upon cooling to 20 C? Solution (a) We are asked to determine how much sugar will dissolve in 1000 g of water at 90 C. From the solubility limit curve in Figure 9.1, at 90 C the maximum concentration of sugar in the syrup is about 77 wt%. It is now possible to calculate the mass of sugar using Equation 4.3 as C sugar (wt%) = m sugar m sugar m water 100 77 wt% = m sugar m sugar 1500 g 100 Solving for m sugar yields m sugar = 5022 g (b) Again using this same plot, at 20 C the solubility limit (or the concentration of the saturated solution) is about 64 wt% sugar. (c) The mass of sugar in this saturated solution at 20 C ( m' sugar ) may also be calculated using Equation 4.3 as follows: 64 wt% = m' sugar m' sugar 1500 g 100 which yields a value for m' sugar of 2667 g. Subtracting the latter from the former of these sugar concentrations yields the amount of sugar that precipitated out of the solution upon cooling m" sugar ; that is m" sugar = m sugar sugar = 5022 g 2667 g = 2355 g
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9.6 At a pressure of 0.01 atm, determine (a) the melting temperature for ice, and (b) the boiling temperature for water. Solution The melting temperature for ice and the boiling temperature for water at a pressure of 0.01 atm may be determined from the pressure-temperature diagram for this system, Figure 10.2, which is shown below; a horizontal line has been constructed across this diagram at a pressure of 0.01 atm. The melting and boiling temperatures for ice at a pressure of 0.01 atm may be determined by moving horizontally across the pressure-temperature diagram at this pressure. The temperature corresponding to the intersection of the Ice-Liquid phase boundary is the melting temperature, which is approximately 1 C. On the other hand, the boiling temperature is at the intersection of the horizontal line with the Liquid-Vapor phase boundary--approximately 16 C. 9.9 Is it possible to have a copper–nickel alloy that, at equilibrium, consists of a liquid phase of composition 20 wt% Ni–80 wt% Cu and also an phase of composition 37 wt% Ni–63 wt% Cu? If so, what will be the approximate temperature of the alloy? If this is not possible, explain why. Solution
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eutectic - Home-work#7 due Friday November 5 2010 W.D...

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