Can you help me with this problem on Xenon?

Question

Consider the following data for Xenon:

 

Triple point: -121°C, 280 torr

Normal melting point: -112°C

Normal boiling point: -107°C

 

Which is more dense, liquid or solid Xe? How do the melting point and boiling point of Xe depend on pressure?

Answer 1

To determine whether the solid or liquid phase of Xenon (Xe) is more dense, we can compare the densities of the solid and liquid phases of Xe at the same temperature and pressure. In this case, we'll compare the density of solid Xe at its normal melting point (-112°C) to the density of liquid Xe at the same temperature.

Now, let's consider how the melting point and boiling point of Xe depend on pressure:

1. **Triple Point Data:** At the triple point of Xe (-121°C, 280 torr), all three phases (solid, liquid, and gas) coexist in equilibrium. This provides information about the conditions at which Xe can exist in each phase simultaneously.

2. **Normal Melting Point:** The normal melting point of Xe is -112°C. This is the temperature at which Xe changes from a solid to a liquid at standard atmospheric pressure (1 atm). At higher pressures, the melting point of Xe generally increases, meaning it requires a higher temperature to melt Xe. This is because increased pressure generally stabilizes the solid phase.

3. **Normal Boiling Point:** The normal boiling point of Xe is -107°C. This is the temperature at which Xe changes from a liquid to a gas at standard atmospheric pressure (1 atm). At higher pressures, the boiling point of Xe generally increases, meaning it requires a higher temperature to boil Xe. This is because increased pressure generally stabilizes the liquid phase.

Regarding which phase is denser at the same temperature and pressure, you would need to compare the densities of solid Xe and liquid Xe at -112°C and 1 atm (standard atmospheric pressure) since that's where the normal melting point occurs. The one with the higher density is denser.

It's worth noting that the density of a substance can vary with temperature and pressure, so you may need to consult a table of physical properties for Xe to obtain the exact values for comparison. However, typically, the density of a solid is higher than that of a liquid for most substances, including noble gases like Xenon.