Using the vapor-pressure curves in Figure 11.25, (d) estimate the external pressure at which diethyl ether will boil at 40 °C.

Key Concepts

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature. It indicates how readily a substance will evaporate; higher vapor pressure means a substance will boil at lower temperatures. Understanding vapor pressure is crucial for determining boiling points under varying external pressures.

Boiling Point

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure surrounding the liquid. At this point, the liquid turns into vapor. For diethyl ether to boil at 40 °C, the external pressure must match its vapor pressure at that temperature, which can be found using vapor-pressure curves.

Phase Equilibrium

Phase equilibrium refers to the state where the rates of the forward and reverse processes of phase changes (like evaporation and condensation) are equal. In the context of boiling, it is the balance between the liquid and vapor phases of a substance. Understanding this concept helps in analyzing how changes in temperature and pressure affect the state of a substance.