Naphthalene (C₁₀H₈) is the main ingredient in traditional mothballs. Its normal melting point is 81 °C, its normal boiling point is 218 °C, and its triple point is 80 °C at 1000 Pa. Using the data, construct a phase diagram for naphthalene, labeling all the regions of your diagram.

Verified step by step guidance

1. Identify the key points for the phase diagram: the triple point, normal melting point, and normal boiling point.
2. Plot the triple point on the phase diagram at 80 °C and 1000 Pa. This is where the solid, liquid, and gas phases coexist.
3. Mark the normal melting point at 81 °C on the temperature axis. Since this is at 1 atm (101325 Pa), draw a line from the triple point to this point to represent the solid-liquid equilibrium line.
4. Mark the normal boiling point at 218 °C on the temperature axis. Again, since this is at 1 atm, draw a line from the normal melting point to this point to represent the liquid-gas equilibrium line.
5. Label the regions: below the solid-liquid line is the solid phase, between the solid-liquid and liquid-gas lines is the liquid phase, and above the liquid-gas line is the gas phase.

Key Concepts

Phase Diagram

A phase diagram is a graphical representation that shows the phases of a substance as a function of temperature and pressure. It typically includes regions representing solid, liquid, and gas phases, as well as lines that indicate phase transitions, such as melting and boiling points. Understanding how to read and construct a phase diagram is essential for visualizing the behavior of substances under varying conditions.

Melting and Boiling Points

The melting point is the temperature at which a solid becomes a liquid, while the boiling point is the temperature at which a liquid turns into a gas. For naphthalene, the melting point is 81 °C and the boiling point is 218 °C. These points are critical for determining the boundaries between different phases in a phase diagram and help in identifying the conditions under which naphthalene exists as a solid, liquid, or gas.

Triple Point

The triple point of a substance is the unique set of conditions at which all three phases (solid, liquid, and gas) coexist in equilibrium. For naphthalene, the triple point occurs at 80 °C and 1000 Pa. This concept is important for constructing a phase diagram, as it marks a specific point where the phase boundaries meet, providing insight into the stability of each phase under varying temperature and pressure.