Question

The phase diagram of a given substance can be characterized by the following information. The normal melting and boiling temperatures are -77.95°C and -33.33°C, respectively, and the triple point pressure and temperature are 6077 Pa and -77.74°C, respectively. The critical point parameters are 112.8 × 10⁵ Pa and 132.35 °C.

1. Make a sketch of the P-T phase diagram (not necessarily to scale) for this substance.
2. Place a point in the phase diagram for the following conditions. State which and how many phases are present at each point

a. -77.74°C, 9506 Pa

b. -77.74°C, 6077 Pa

c. -27.7°C, 101,325 Pa

d. 141.85°C, 105 × 10⁵ Pa

3. What is this substance phase at normal conditions (1 atm and 25°C)?
4. Which phase does have a higher density, the solid or liquid?
5. Does this substance have a negative or positive slope for its solid-liquid boundary? What does that imply?

Answer 1

B. Liquid phase has higher density.

C. This substance have negative slope for it's solid liquid boundary. It implies that this substance expands on cooling. Water also shows this type of characteristic.