To determine the phase of CO₂ at 72 bar and 0°C, we'll need to refer to the phase diagram of carbon dioxide (CO₂). A phase diagram shows the state of a substance (solid, liquid, or gas) at various temperatures and pressures.
1. Sublimation Point: The sublimation point of CO₂ is -78.5°C at 1 bar, where it transits directly from solid to gas.
2. Triple Point: The triple point of CO₂ is at 5.11 bar and -56.4°C, where CO₂ can coexist in solid, liquid, and gas phases.
3. Critical Point: The critical point of CO₂ is at 73 bar and 31.1°C, above which CO₂ cannot exist as a liquid, but only as a supercritical fluid.
Given coordinates:
- Temperature: 0°C
- Pressure: 72 bar
Now, let's analyze the phase diagram based on these coordinates:
1. Pressure Analysis:
- The given pressure (72 bar) is just below the critical pressure (73 bar), where the CO₂ could either be in liquid or supercritical phase.
2. Temperature Analysis:
- The given temperature (0°C) is well below the critical temperature (31.1°C), suggesting that CO₂ can exist as a liquid because it’s not crossing the critical temperature line.
From these points on the phase diagram:
- Since the temperature of 0°C is below the critical temperature of 31.1°C.
- And the pressure of 72 bar is very close to, but just below, the critical pressure of 73 bar.
Therefore, at 72 bar and 0°C, carbon dioxide (CO₂) will be in the liquid phase.
