Which of the following processes are spontaneous and which...

Which of the following processes are spontaneous and which are nonspontaneous: (a) the ripening of a banana, (b) dissolution of sugar in a cup of hot coffee, $(\mathrm{c})$ the reaction of nitrogen atoms to form $\mathrm{N}_{2}$ molecules at $25^{\circ} \mathrm{C}$ and $1 \mathrm{~atm},$ (d) lightning, (e) formation of $\mathrm{CH}_{4}$ and $\mathrm{O}_{2}$ molecules from $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ at room temperature and 1 atm of pressure?

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Key Concepts

Gibbs Free Energy

Gibbs Free Energy (?G) is a central concept in thermodynamics that determines the spontaneity of a process. If ?G is negative, the process can occur spontaneously under constant temperature and pressure. This concept links the system's enthalpy (?H) and entropy (?S) changes through the equation ?G = ?H - T?S, providing a quantitative measure of a reaction’s driving force.

Enthalpy and Entropy Contributions

Enthalpy (?H) represents the heat absorbed or released during a process, while entropy (?S) measures the change in disorder or randomness. The balance between these two factors, especially under varying temperature conditions, is crucial. A process with a favorable balance (for example, exothermic reactions with increasing disorder) often results in a negative ?G, indicating spontaneity.

Thermodynamic vs Kinetic Control

It’s important to distinguish between thermodynamic and kinetic aspects of a reaction. A process may be thermodynamically spontaneous (negative ?G) yet proceed very slowly if it has a high activation energy barrier. Hence, kinetics (the study of reaction rates and mechanisms) complements thermodynamic analysis, as some spontaneous processes might require an initial energy input to overcome kinetic hurdles.

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