Phase Diagram for a Solution

Advertisements
Advertisements

Related Posts:


This phase diagram indicates the pressure in atmospheres of water and a solution at various temperatures. The graph shows the freezing point of water and the freezing point of the solution, with the difference between these two values identified as delta T subscript f. The graph shows the boiling point of water and the boiling point of the solution, with the difference between these two values identified as delta T subscript b. Similarly, the difference in the pressure of water and the solution at the boiling point of water is shown and identified as delta P. This difference in pressure is labeled vapor pressure lowering. The lower level of the vapor pressure curve for the solution as opposed to that of pure water shows vapor pressure lowering in the solution. Background colors on the diagram indicate the presence of water and the solution in the solid state to the left, liquid state in the central upper region, and gas to the right.
Figure 1. Phase diagrams for a pure solvent (solid curves) and a solution formed by dissolving nonvolatile solute in the solvent (dashed curves). Source: OpenStax Chemistry 2e

Phase Diagram for a Solution (OpenStax Chemistry 2e)

The colligative effects on vapor pressure, boiling point, and freezing point described in the previous section are conveniently summarized by comparing the phase diagrams for a pure liquid and a solution derived from that liquid (Figure 1).

The liquid-vapor curve for the solution is located beneath the corresponding curve for the solvent, depicting the vapor pressure lowering, ΔP, that results from the dissolution of nonvolatile solute. Consequently, at any given pressure, the solution’s boiling point is observed at a higher temperature than that for the pure solvent, reflecting the boiling point elevation, ΔTb, associated with the presence of nonvolatile solute. The solid-liquid curve for the solution is displaced left of that for the pure solvent, representing the freezing point depression, ΔTf, that accompanies solution formation. Finally, notice that the solid-gas curves for the solvent and its solution are identical. This is the case for many solutions comprising liquid solvents and nonvolatile solutes. Just as for vaporization, when a solution of this sort is frozen, it is actually just the solvent molecules that undergo the liquid-to-solid transition, forming pure solid solvent that excludes solute species. The solid and gaseous phases, therefore, are composed of solvent only, and so transitions between these phases are not subject to colligative effects.

Source:

Flowers, P., Theopold, K., Langley, R., & Robinson, W. R. (2019, February 14). Chemistry 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/books/chemistry-2e

Advertisements
Advertisements

Related Research

Research Article: Investigating global phase diagrams (GPDs) with reentrant transition behavior

Date Published: July 12, 2018 Publisher: Public Library of Science Author(s): Jude Simons Bayor, Baohua Teng, Lingli Wang, Nikolaos Fytas. http://doi.org/10.1371/journal.pone.0199459 Abstract: In this paper we calculate the global phase diagrams with the closed-loop behavior for the phase transition of physical systems by means of the transverse field Ising model with nearest neighbor interaction. The … Continue reading

Research Article: The Cu-Li-Sn Phase Diagram: Isopleths, Liquidus Projection and Reaction Scheme

Date Published: October 27, 2016 Publisher: Public Library of Science Author(s): Siegfried Fürtauer, Hans Flandorfer, Amitava Mukherjee. http://doi.org/10.1371/journal.pone.0165058 Abstract: The Cu-Li-Sn phase diagram was constructed based on XRD and DTA data of 60 different alloy compositions. Eight ternary phases and 14 binary solid phases form 44 invariant ternary reactions, which are illustrated by a Scheil-Schulz … Continue reading

Research Article: Experimental Investigation of the Cd-Pr Phase Diagram

Date Published: April 9, 2014 Publisher: Public Library of Science Author(s): Thomas L. Reichmann, Herta S. Effenberger, Herbert Ipser, Andreas Hofmann. http://doi.org/10.1371/journal.pone.0094025 Abstract: The complete Cd-Pr equilibrium phase diagram was investigated with a combination of powder-XRD, SEM and DTA. All intermetallic compounds within this system, already reported in literature, could be confirmed: CdPr, Cd2Pr, Cd3Pr, … Continue reading

Research Article: Phase diagrams and dynamics of a computationally efficient map-based neuron model

Date Published: March 30, 2017 Publisher: Public Library of Science Author(s): Mauricio Girardi-Schappo, Germano S. Bortolotto, Rafael V. Stenzinger, Jheniffer J. Gonsalves, Marcelo H. R. Tragtenberg, Dante R. Chialvo. http://doi.org/10.1371/journal.pone.0174621 Abstract: We introduce a new map-based neuron model derived from the dynamical perceptron family that has the best compromise between computational efficiency, analytical tractability, reduced … Continue reading