Calculate the free energy change for this reaction at 25^∘ C. Is the reaction spontaneous? (Assu

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Calculate the free energy change for this reaction at 25^∘...

Calculate the free energy change for this reaction at $25^{\circ} \mathrm{C}$. Is the reaction spontaneous? (Assume that all reactants and products are in their standard states.) $$ \begin{array}{c} 2 \mathrm{Ca}(s)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CaO}(s) \\ \Delta H_{\mathrm{rxn}}^{\circ}=-1269.8 \mathrm{~kJ} ; \Delta S_{\mathrm{rxn}}^{\circ}=-364.6 \mathrm{~J} / \mathrm{K} \end{array} $$

Calculate the free energy change for this reaction at $25^{\circ} \mathrm{C}$. Is the reaction spontaneous? (Assume that all reactants and products are in their standard states.)
$$
\begin{array}{c}
2 \mathrm{Ca}(s)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CaO}(s) \\
\Delta H_{\mathrm{rxn}}^{\circ}=-1269.8 \mathrm{~kJ} ; \Delta S_{\mathrm{rxn}}^{\circ}=-364.6 \mathrm{~J} / \mathrm{K}
\end{array}
$$

Key Concepts

Gibbs Free Energy

Gibbs free energy (?G) is a thermodynamic quantity that indicates the maximum amount of useful work obtainable from a chemical reaction at constant temperature and pressure. It combines the effects of enthalpy (heat content) and entropy (degree of disorder) to determine whether a process is spontaneous; a negative ?G signifies that the reaction can proceed without external energy input.

Enthalpy

Enthalpy (?H) is a measure of the total heat content of a system during a reaction at constant pressure. It represents the energy absorbed or released in a reaction. Exothermic reactions, which release heat (indicated by a negative enthalpy change), tend to favor spontaneity if the entropy change is not overwhelmingly negative.

Entropy

Entropy (?S) is a measure of the disorder or randomness of a system. It plays a critical role in determining reaction spontaneity. A positive entropy change generally means increased disorder, which favors spontaneity, while a negative change works against spontaneity when combined with enthalpy in the Gibbs free energy equation.

Reaction Spontaneity

Reaction spontaneity is determined by the sign of the Gibbs free energy change and indicates whether a reaction can occur on its own without the input of additional energy. When ?G is negative, the process is thermodynamically favorable, whereas a positive ?G means the reaction is non-spontaneous under the given conditions.

Standard State Conditions

Standard state conditions refer to a set of agreed upon reference conditions (typically 1 bar pressure for gases and pure substances in their most stable forms at a specified temperature, often 25°C) that are used to report thermodynamic data such as standard enthalpy and entropy changes. This allows for consistent calculations and comparisons across different reactions.

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