What is the normal freezing point of this unknown substance?

• A. 0 °C
• B. –200 °C
• C. 200 °C
• D. 400 °C
• E. 100 °C

Answer: (E)

Verified step by step guidance

1. Identify the normal freezing point as the temperature at which the substance transitions from liquid to solid at 1 atm pressure.
2. Locate the horizontal dashed line on the graph that represents the pressure of 1.00 atm.
3. Find the point where the solid-liquid phase boundary intersects the 1.00 atm pressure line; this point corresponds to the normal freezing point.
4. Read the temperature value on the x-axis at this intersection point to determine the normal freezing point.
5. Note that the graph shows this intersection at approximately 100 °C, indicating the normal freezing point of the substance.