Direct measurement of the normal boiling point of hydrogen...

Direct measurement of the normal boiling point of hydrogen peroxide is not possible because pure $\mathrm{H}_{2} \mathrm{O}_{2}$ explodes on heating. The boiling point can be estimated, however, from vapor-pressure data. Use the vapor pressures of 75.0 $\mathrm{mm}$ Hg at $89.0^{\circ} \mathrm{C}$ and 319.2 $\mathrm{mm}$ Hg at $125.0^{\circ} \mathrm{C}$ to estimate the boiling point. Compare your result with the value given in Section 18.11 .

Key Concepts

Clausius-Clapeyron Equation

The Clausius-Clapeyron equation provides a quantitative relationship between vapor pressure and temperature. It is often used to estimate the enthalpy of vaporization and to extrapolate boiling points from vapor pressure data by assuming that the enthalpy of vaporization is relatively constant over the temperature range of interest.

Normal Boiling Point

The normal boiling point is defined as the temperature at which a liquid's vapor pressure equals standard atmospheric pressure (usually 1 atm). This concept is fundamental in physical chemistry as it characterizes a substance’s volatility and phase change behavior under normal conditions.

Vapor Pressure

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid (or solid) phase at a given temperature. It is a key parameter in understanding phase transitions, and variations in vapor pressure with temperature help determine important thermodynamic properties such as the boiling point.

Extrapolation from Vapor-Pressure Data

Extrapolation in thermodynamics involves using known vapor pressure data at various temperatures to predict the properties of a system at temperatures beyond the measured range. For instance, by applying the Clausius-Clapeyron equation to available vapor pressure data, one can estimate the boiling point of a substance under conditions where direct measurement is impractical or dangerous.

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