The sublimation of carbon dioxide at -78^∘ C is given by...

The sublimation of carbon dioxide at $-78^{\circ} \mathrm{C}$ is given by $$\mathrm{CO}_{2}(s) \longrightarrow \mathrm{CO}_{2}(g) \quad \Delta H_{\mathrm{sub}}=25.2 \mathrm{kJ} / \mathrm{mol}$$Calculate $\Delta S_{\text {sub }}$ when $84.8 \mathrm{g}$ of $\mathrm{CO}_{2}$ sublimes at this temperature.

Key Concepts

Phase Transition

A phase transition refers to the process in which a substance changes its state, such as from a solid to a gas in sublimation. This concept is central to thermodynamics as it involves changes in energy and order, and it requires an understanding of how matter transforms between different phases under various conditions.

Enthalpy Change (?H)

Enthalpy change represents the heat absorbed or released during a process at constant pressure. In the context of phase transitions, the enthalpy change quantifies the energy required to overcome intermolecular forces, which is crucial for understanding the energy balance during sublimation or other physical changes.

Entropy Change (?S) and Its Calculation

Entropy change measures the increase or decrease in disorder within a system during a process. In equilibrium phase transitions, the relationship ?S = ?H/T is used to calculate the entropy change, linking the absorbed or released heat (enthalpy change) to the temperature at which the transition occurs. This concept helps in determining the spontaneity and feasibility of the process.

Mole Conversion

The mole concept is fundamental in chemistry for converting the mass of a substance to the number of particles or moles using its molar mass. This conversion is essential in thermodynamic calculations where energy changes and properties like enthalpy and entropy are expressed on a per mole basis, ensuring accurate and consistent quantification of the process involved.

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