Chemistry

Question Analysis
This question tests the student's understanding of the behavior of substances at and above their critical points.

Key Concept Explanation
The critical point is the highest temperature and pressure at which a substance can exist as a liquid and a gas. Above the critical point, the substance exists as a supercritical fluid, which has properties of both liquids and gases.

Step-by-step Solution
1. Identify the critical point: 500 K and 80 atm.
2. Determine the given conditions: T = 500 K, P = 90 atm.
3. Since the pressure (90 atm) is above the critical pressure (80 atm) and the temperature (500 K) is at the c...