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Ch.19 - Free Energy & Thermodynamics
Tro - Chemistry: A Molecular Approach 6th Edition
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Tro 6th EditionCh.19 - Free Energy & Thermodynamics문제 44a
19장, 문제 44a

Given the values of ΔH°rxn, ΔS°rxn, and T, determine ΔSuniv and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) a. ΔH°rxn = -75 kJ; ΔS°rxn = -127 J/K; T = 298 K

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Convert \( \Delta H^\circ_{rxn} \) from kJ to J by multiplying by 1000, since \( \Delta S^\circ_{rxn} \) is given in J/K.
Calculate \( \Delta S_{univ} \) using the formula: \( \Delta S_{univ} = \Delta S^\circ_{rxn} - \frac{\Delta H^\circ_{rxn}}{T} \).
Substitute the given values into the formula: \( \Delta S_{univ} = -127 \text{ J/K} - \frac{-75000 \text{ J}}{298 \text{ K}} \).
Simplify the expression to find \( \Delta S_{univ} \).
Determine the spontaneity of the reaction: if \( \Delta S_{univ} > 0 \), the reaction is spontaneous; if \( \Delta S_{univ} < 0 \), it is non-spontaneous.

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주요 개념

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

Gibbs Free Energy

Gibbs Free Energy (G) is a thermodynamic potential that helps predict the spontaneity of a reaction 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, while a positive ΔG suggests it is non-spontaneous.
추천 영상:
가이드 코스
01:51
Gibbs Free Energy of Reactions

Entropy (ΔS)

Entropy (ΔS) is a measure of the disorder or randomness in a system. In the context of chemical reactions, it quantifies the change in disorder as reactants transform into products. A positive ΔS indicates an increase in disorder, which generally favors spontaneity, while a negative ΔS suggests a decrease in disorder, which can hinder spontaneity.
추천 영상:
가이드 코스
02:46
Entropy in Thermodynamics

Enthalpy (ΔH)

Enthalpy (ΔH) is a measure of the total heat content of a system and reflects the energy changes during a chemical reaction. A negative ΔH indicates that the reaction is exothermic, releasing heat, which often contributes to spontaneity. Conversely, a positive ΔH indicates an endothermic reaction, absorbing heat, which may require a favorable entropy change to be spontaneous.
추천 영상:
가이드 코스
02:34
Enthalpy of Formation
관련 실천
교과서 질문

Given the values of ΔH°rxn, ΔS°rxn, and T, determine ΔSuniv and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) c. ΔH°rxn = +75 kJ; ΔS°rxn = -127 J/K; T = 298 K

교과서 질문

Calculate ΔSsurr at the indicated temperature for each reaction. d. ΔH°rxn = +114 kJ; 77 K

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교과서 질문

Calculate the change in Gibbs free energy for each of the sets of ΔH°rxn, ΔS°rxn, and T given in Problem 44. Predict whether or not each reaction is spontaneous at the temperature indicated. (Assume that all reactants and products are in their standard states.)

교과서 질문

Given the values of ΔH°rxn, ΔS°rxn, and T, determine ΔSuniv and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) c. ΔH°rxn = -135 kJ; ΔS°rxn = -282 J>K; T = 298 K

교과서 질문

Given the values of ΔH°rxn, ΔS°rxn, and T, determine ΔSuniv and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) a. ΔH°rxn = +135 kJ; ΔS°rxn = -282 J/K; T = 298 K

교과서 질문

Calculate the free energy change for this reaction at 25 °C. Is the reaction spontaneous? (Assume that all reactants and products are in their standard states.) 2 Ca(s) + O2( g) → 2 CaO(s) ΔH°rxn = -1269.8 kJ; ΔS°rxn = -364.6 J/K

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