Construct a qualitative phase diagram for the Sn / Sb system, which has binary eutectics at 92 %

Construct a qualitative phase diagram for the Sn / Sb...

Construct a qualitative phase diagram for the $\mathrm{Sn} / \mathrm{Sb}$ system, which has binary eutectics at $92 \%$ and $95 \%$ Sn that melt at $199^{\circ} \mathrm{C}$ and $240^{\circ} \mathrm{C}$, respectively. The melting points of tin and antimony are $231.9^{\circ} \mathrm{C}$ and $630.5^{\circ} \mathrm{C}$.

Key Concepts

Eutectic Reaction

A eutectic reaction occurs in a binary system when a single liquid phase transforms into two distinct solid phases simultaneously at a specific composition and temperature. This reaction is identified by a unique eutectic point, which is characteristic of a minimum melting temperature in the system.

Melting Temperature

The melting temperature is the specific temperature at which a substance transitions from a solid to a liquid state. In the context of phase diagrams, the melting points of pure components and eutectic mixtures are fundamental in defining the phase boundaries and overall structure of the diagram.

Phase Diagram

A phase diagram is a graphical tool used to illustrate the equilibrium states of matter in a system as a function of variables such as temperature and composition. It provides information on which phases are present under different conditions and includes boundaries that indicate phase transitions.

Binary Alloy System

A binary alloy system involves two different elemental components. The phase diagram of such a system maps how these two elements combine over a range of compositions and temperatures, highlighting regions where single or multiple phases are stable.

Qualitative Analysis of Phase Diagrams

Qualitative analysis of a phase diagram emphasizes understanding the general features and trends—such as phase regions, phase boundaries, and invariant reactions—without requiring precise numerical data. This approach is useful for constructing a simplified overview of the system's behavior.

Transcript

00:01 In this question, we're going to be constructing the phase diagram of oxygen.

00:07 So to start, they give us a bunch of different information about the transitions of oxygen as it moves between the phases.

00:16 So to start, they give us the normal melting point at negative 218 degrees celsius.

00:22 So a phase diagram has on both of its axes, temperature versus pressure.

00:27 And i went ahead and put temperature in degrees celsius and then pressure in 18.

00:31 And so for the temperature that they provide us for the normal melting point, they give us negative to 18 degrees celsius.

00:40 And to start, we're going to go ahead and label our sections.

00:43 So right here we have our solid phase.

00:49 And then right here we have our liquid phase.

00:53 And here we have our gas phase.

00:56 And i hope this makes sense that a higher temperature at a lower pressure would be in the gas phase, but a higher temperature, as we move up this to a higher pressure, we would go into the liquid phase, and then at a higher pressure and lower temperatures, we would be in the solid phase.

01:14 Okay? and so now we can go ahead and start labeling this.

01:17 So at our melting point, we would have negative to 18 degrees celsius.

01:23 So a normal melting point, when it means normal, it means standard pressure.

01:28 So we can do a standard atmospheric pressure, which would be one atm.

01:32 So i'm going to go ahead and put right here as one atm.

01:38 And then on this axis, we're going to go ahead and label it as negative to 18 degrees celsius and 1 atm.

01:49 Sorry, that was really small.

01:50 Okay.

01:51 And so then for the normal boiling point where it's going from liquid to gas, that's going to be at negative 183.

01:59 So that's going to be at the same pressure because it's still the normal boiling point.

02:02 So we're going to go ahead and extend this line for this axis, and then we'll go ahead and bring it down...

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