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Entropy of vaporization, denoted as \( \Delta S_{vap} \), measures the change in entropy when a substance transitions from a liquid to a gas. This concept is pivotal in thermodynamics as it describes the degree of disorder or randomness introduced in the system as molecules move from being closely packed in a liquid state to being spread out in a gaseous state.
For example, when carbon tetrachloride, \( \text{CCl}_4 \), vaporizes, the entropy increases due to the greater spacing between molecules in the vapor phase. To compute the entropy of vaporization, use the formula:
\[\Delta S_{vap} = \frac{\Delta H_{vap}}{T_b}\]where \(\Delta H_{vap}\) is the enthalpy of vaporization, and \(T_b\) is the boiling point temperature in Kelvin.
This equation highlights the relationship between enthalpy and entropy, providing insight into how much energy disperses during vaporization.

The enthalpy of vaporization, \( \Delta H_{vap} \), is the amount of energy required to convert one mole of a liquid into its gaseous state at constant pressure. It essentially represents the energy needed to overcome intermolecular forces in the liquid.
For carbon tetrachloride, this value is \( 29.82 \, \text{kJ/mol} \).
This value is significant because it indicates the strength of intermolecular attractions: stronger forces require more energy to break, resulting in a higher enthalpy.

• Enthalpy is dependent on the nature of the liquid.
• Temperature can also affect the value slightly.

For computations in thermodynamics, it's common to convert enthalpy from kilojoules per mole to joules per mole for consistency in units when calculating entropy or free energy.

Gibbs free energy, denoted as \( \Delta G \), is a thermodynamic quantity serving as an indicator of spontaneity for a process. It combines enthalpy, entropy, and temperature, expressed by:
\[\Delta G = \Delta H - T\Delta S\]If \( \Delta G \) is negative, the process occurs spontaneously.
During the vaporization of carbon tetrachloride at \( 25^{\circ} \mathrm{C} \), we calculate \( \Delta G_{vap} \) using the given enthalpy and the previously calculated entropy.

• \( \Delta G \) gives insight into the feasibility of vaporization under non-boiling conditions.
• The enthalpy and entropy values guide the direction and magnitude of the free energy.

The calculations reveal \( \Delta G_{vap}^\circ = 426.67 \, \text{J/mol} \), showing that vaporization at this temperature is not entirely spontaneous, as the process would not result in a large energy decrease.