Chemistry 2214A/B Lecture Notes - Lecture 17: Molar Volume, Indium Phosphide, Phase Transition

44 views2 pages

OC389922

29 Jan 2015

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

The gibb"s free energy g, of a system where two phases, liquid (l) and gas (g) are at equilibrium (a point on the curve). This is the slope of the boundary (generally + ve, there are exceptions) clapeyron equation in differential form. The result: is the integrated form of the clapeyron equation, good approx. for a small temp. range. It follows that ln p can be expressed as: A plot of lnp vs 1/t will yield a straight line with a slope = - b = hvap /r and an intercept = a. Chemical potential (molar gibbs energy) and phase stability (response to t and p changes) Temperature dependence of phase stability: all slopes (in the solid, liq. and gas phase) are ve, the steepest slope is found in the gas phase sm(g) > sm(l) > sm(s, discontinuity at phase transition (melting, boiling point)

Related Questions

Given that the density of liquid water is 0.958 g/mL and thedensity of water vapor is 0.5983 g/L at the normal boiling point,compute the boiling point of water on a mountain top where thepressure is 0.90 atm.
Hint: Use the form of Clausius Clapeyron where you leave thepressure dependence on T in the ln form.
Hint: Remember it takes longer to cook food on mountains.
What is the Boiling point at higher elevation: ________K [Report to3 significant figures.]

Suppose the (1) + (2) system exhibits liquid-liquid immiscibility. Suppose we are at a state where G1/RT = 0.1 and G2/RT = 0.3. The Gibbs energy of mixing quantifies the Gibbs energy of the mixture relative to the Gibbs energies of the pure components. Suppose the excess Gibbs energy for the (1) + (2) mixture is given by: GE/RT = 2.5 x1 x2

a. Combine this with the Gibbs energy for ideal mixing to calculate the Gibbs energy of mixing across the composition range and plot the results against x1 to illustrate that the system exhibits immiscibility.

b. Draw a tangent to the humps to illustrate that the system is one phase at compositions greater than z1 = 0.854 and less than z1 = 0.145, but will split into two phases with compositions at any intermediate overall composition. Most systems with liquid-liquid immiscibility must be modeled with a more complex formula for excess Gibbs energy. The humps on the diagram are usually offcenter, as in Fig. 14.3 on page 545 in the text. The simple model used for the calculations here results in the symmetrical diagram.

c. When a mixture splits into two phases, the over-all fractions (of total moles) of the two phases are found by the lever rule along the composition coordinate. Suppose 0.6 mol of (1) and 0.4 mol of (2) are mixed. Use the lever rule to calculate the total number of moles which would be found in each phase of the actual system. Designate the (1)-rich phase as the Î² phase.

d. What is the value of the hypothetical Gibbs energy, (expressed as G/RT), of a mixture of 0.6 mol of (1) and 0.4 mol of (2) if the mixture were to remain as one phase? Calculate the Gibbs energy of the total system considering the phase split into two phases, and show that the Gibbs energy is less than the Gibbs energy of the single-phase system.

Chemistry 2214A/B Lecture Notes - Lecture 17: Molar Volume, Indium Phosphide, Phase Transition

Document Summary

Get access

Related Documents

Chemistry 2214A/B Lecture Notes - Lecture 2: Ideal Gas, Horse Length, Root Mean Square

Chemistry 2214A/B Lecture Notes - Lecture 7: Phase Transition, Isochoric Process, Calorimetry

PHYS 106L Chapter Notes - Chapter 7: Vapor Pressure, Viscous Liquid, Cloud Condensation Nuclei

Related Questions