University:
The Pennsylvania State University
Course:
CHEM 450 | Thermodynamics
Academic year:

2024
Views:

310

Pages:

3
Author:

Alexis H.

Problem Set #41 Assigned: April 12, 2024 Due: April 15, 2024 at 2:30 pm 1. Methyl ethyl ether and diborane (B2H6) react to form a single compound with 1:1 stoichiometry. This compound is associated with a maximum melting temperature in the phase diagram at 133 K. The solid/liquid phase diagram contains two eutectic points. The first one is at 25 mol% diborane and 123 K, while the second one occurs at 90 mol% diborane 104 K. The melting point of pure methyl ethyl either is 131 K, while pure diborane melts at 110 K. Construct a phase diagram for this system. You can assume that methyl ethyl ether and diborane are both immiscible in the solid phase with the 1:1 compound that is formed by reacting these two chemicals. The following figure from your textbook shows the generic case for two chemicals that form a compound with two eutectic points: 2. (a) How many phases can be in equilibrium in a ternary phase diagram (3 component system) at constant temperature and pressure? (b) Can the lever rule be employed in a ternary phase diagram? Construct a ternary phase diagram as part of your answer. (c) In class I noted that you couldn’t construct as phase diagram for four components at constant temperature and pressure on a piece of paper in two dimensions. Could you do it in three dimensions? What geometric shape would be necessary? What would you need to do to visualize the phases in such a system? 3. Explain the difference between activity and concentration. What factors account for the difference between the two? 4. The vapor pressure of water in a saturated solution of calcium nitrate at 20 °C is 1.381 kPa. By contrast, the vapor pressure of pure water is 2.3393 kPa at the same temperature. What is the activity of the water? 5. By measuring the equilibrium between liquid and vapor phases of a propanone (P) and methanol (M) solution at 57.2 °C at 1 atm, it was found that xP = 0.400 when yp = 0.516. Find the activity and the activity coefficients of both components for this system benchmarked against Raoult’s law. The vapor pressure of the pure components are: pp* = 105 kPa and pM* = 73.5 kPa. Remember xp is the mole fraction of propanone in the liquid phase and yp is the mole fraction of propanone in the vapor phase. 1 131k eutectic eutecq 110k 5 85 98 BA Composition 2 (a) 4 phases (b) Yes you can. A C B (c) You would be able to construct it in three dimensions except this time it would be shaped as a cube. To visualize the system you would picture each corner of a square as 100% of each component and as you move to the middle the more mixed the composition becomes. 3 Activity is a measure of the e ective concentration of a species in a mixture, therefore as the concentration of a substance increases, the activity will also increase. Meanwhile concentration is the amount of a substance in a de ned space. 4 p x.p x 5 iiiiiij.ua 1 as 1.11 0.5909 actingotwater of activity water 0.5909 I ai