For a certain chemical reaction, ΔH° = -35.4 kJ and ΔS° = -85.5 J/K. (c) Calculate ΔG° for the reaction at 298 K. (d) Is the reaction spontaneous at 298 K under standard conditions?

검증된 단계별 안내

To calculate the standard Gibbs free energy change (ΔG°) for the reaction, use the equation: ΔG° = ΔH° - TΔS°. Here, ΔH° is given in kJ, so convert ΔS° from J/K to kJ/K by dividing by 1000.

Substitute the given values into the equation: ΔG° = (-35.4 kJ) - (298 K) * (-85.5 J/K / 1000).

Perform the multiplication: (298 K) * (-85.5 J/K / 1000) to find the TΔS° term in kJ.

Subtract the TΔS° value from ΔH° to find ΔG°.

To determine if the reaction is spontaneous at 298 K, check the sign of ΔG°. If ΔG° is negative, the reaction is spontaneous under standard conditions.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Gibbs Free Energy (ΔG°)

Gibbs Free Energy (ΔG°) is a thermodynamic potential that measures the maximum reversible work obtainable from a thermodynamic system at constant temperature and pressure. It is calculated using the equation ΔG° = ΔH° - TΔS°, where ΔH° is the change in enthalpy, T is the temperature in Kelvin, and ΔS° is the change in entropy. A negative ΔG° indicates that a reaction is spontaneous under the given conditions.

Enthalpy (ΔH°)

Enthalpy (ΔH°) is a measure of the total heat content of a system and reflects the energy required to break and form bonds during a chemical reaction. A negative ΔH° value, such as -35.4 kJ, indicates that the reaction releases heat, making it exothermic. This release of energy can contribute to the spontaneity of the reaction.

Entropy (ΔS°)

Entropy (ΔS°) is a measure of the disorder or randomness in a system. A negative ΔS° value, like -85.5 J/K, suggests that the reaction leads to a decrease in disorder, which can hinder spontaneity. In thermodynamics, the balance between enthalpy and entropy changes determines whether a reaction will occur spontaneously at a given temperature.