El elemento cesio (Cs) se congela a 28.4^∘ C, y su entalpia molar de fusión es ΔHfus =2.09 kJ /

step 1 option a when the molten is solidified to cesium at its normal melting point then delta s is equ

El elemento cesio (Cs) se congela a 28.4^∘ C, y su entalpia...

El elemento cesio (Cs) se congela a $28.4^{\circ} \mathrm{C}$, y su entalpia molar de fusión es $\Delta H_{\text {fus }}=2.09 \mathrm{~kJ} / \mathrm{mol}$. (a) Cuando el cesio fundido se solidifica a $\mathrm{Cs}(s)$ en su punto de fusión normal, ¿es positivo o negativo el $\Delta S$ ? (b) Calcule el valor de $\Delta S$ cuando $15.0 \mathrm{~g}$ de $\mathrm{Cs}(l)$ solidifican a $28.4^{\circ} \mathrm{C}$.

Key Concepts

Phase Transition

A phase transition involves the change from one state of matter to another, such as from liquid to solid. These transitions involve latent heat and are accompanied by changes in the order of the system. Typically, when a liquid solidifies, the ordered structure of a solid forms from a disordered liquid, which results in a decrease in entropy.

Entropy

Entropy is a measure of the disorder or randomness in a system. In thermodynamics, changes in entropy indicate how the distribution of energy and states evolves during physical transformations. It is fundamental in predicting the spontaneous direction of processes, with systems generally moving towards higher entropy, unless work is done on them.

Thermodynamic Relationship Between Enthalpy and Entropy

The relationship ?S = ?H/T is used to connect the enthalpy change (?H) of a phase transition with its corresponding entropy change (?S) at a constant temperature (T). This formula is especially useful for phase changes occurring at a constant temperature, such as melting or freezing, and underscores the interplay between energy and disorder.

Molar Conversion

Molar conversion involves translating a given mass of a substance into the number of moles using the substance's molar mass. This step is essential when working with molar thermodynamic quantities such as molar enthalpy or molar entropy, as it allows for the proper scaling of these properties to the amount of substance undergoing the phase change.

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