Question

phase diagram
use the diagram to answer each question.

1. which section represents the solid phase?
2. which section represents the liquid phase?
3. which section represents the gas phase?
4. which letter represents the triple point?
5. which letter represents the critical point?
6. what is this substances normal melting point?
7. what is this substances normal boiling point?
8. above what temperature is it impossible to liquify this substance no matter what the pressure?
9. at what temperature and pressure do all three phases coexist?
10. is the density of the solid greater than or less than the density of the liquid?
11. would an increase in pressure cause this substance to freeze or melt?

Explanation:

• Solid phase: In a phase diagram, the solid phase is typically at lower temperatures and higher pressures. Section A fits this description.
• Liquid phase: The liquid phase is usually in an intermediate region. Section B is in the middle - temperature and pressure range.
• Gas phase: The gas phase is at higher temperatures and lower pressures. Section C is in this region.
• Triple point: The triple point is the point where all three phases co - exist. Point d is where the three phase - boundary lines meet.
• Critical point: The critical point is the end - point of the liquid - vapor co - existence curve. Point e is at the end of the curve.
• Normal melting point: The normal melting point is the temperature at which the solid - liquid equilibrium occurs at 1 atmosphere. At 1 atmosphere (pressure = 1.0), the solid - liquid transition occurs at \(65^{\circ}C\).
• Normal boiling point: The normal boiling point is the temperature at which the liquid - gas equilibrium occurs at 1 atmosphere. At 1 atmosphere (pressure = 1.0), the liquid - gas transition occurs at \(100^{\circ}C\).
• Impossible to liquify: Above the critical temperature, it is impossible to liquify the substance no matter the pressure. The critical temperature is \(110^{\circ}C\).
• Three phases co - exist: At the triple point (\(45^{\circ}C\) and the pressure corresponding to point d, say \(P_d\) (approx 0.25 atm, but exact value from the diagram's pressure scale at point d)).
• Density of solid vs liquid: The slope of the solid - liquid phase boundary is positive. For a substance with a positive slope of the solid - liquid phase boundary, the density of the solid is greater than the density of the liquid.
• Effect of pressure increase: Since the slope of the solid - liquid phase boundary is positive, an increase in pressure will cause the substance to freeze (move from liquid to solid as pressure increases at a constant temperature).

Answer:

• Solid phase: A
• Liquid phase: B
• Gas phase: C
• Triple point: d
• Critical point: e
• Normal melting point: \(65^{\circ}C\)
• Normal boiling point: \(100^{\circ}C\)
• Impossible to liquify above: \(110^{\circ}C\)
• Three phases co - exist: \(45^{\circ}C\) and the pressure at point d (approx 0.25 atm from the diagram's pressure scale at d)
• Density of solid: greater than liquid
• Effect of pressure increase: freeze