The critical point of this substance occurs at what temperature?

• A. 0 °C
• B. –78.5 °C
• C. –56.7 °C
• D. 31 °C
• E. 100 °C

Answer: (D)

Verified step by step guidance

1. Identify the critical point on the phase diagram, which is the point at the end of the liquid-gas boundary curve where the liquid and gas phases become indistinguishable.
2. Look for the temperature value on the x-axis corresponding to this critical point, which is typically marked at the top right end of the liquid-gas boundary.
3. From the diagram, observe that the critical point is located at the temperature of 31 °C on the x-axis.
4. Understand that the critical temperature is the highest temperature at which a substance can exist as a liquid, regardless of pressure.
5. Conclude that the critical temperature of the substance is 31 °C based on the phase diagram.