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Ch.19 - Free Energy & Thermodynamics
Tro - Chemistry: A Molecular Approach 5th Edition
Tro5th EditionChemistry: A Molecular ApproachISBN: 9780134874371당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Tro 5th EditionCh.19 - Free Energy & Thermodynamics문제 55
19장, 문제 55

Use data from Appendix IIB to calculate ΔSrxn ° for each of the reactions. In each case, try to rationalize the sign of ΔSrxn ° . a. C2H4(g) + H2(g) → C2H6(g)

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Identify the substances involved in the reaction: C2H4(g), H2(g), and C2H6(g).
Use Appendix IIB to find the standard molar entropy (S°) values for each substance: S°(C2H4), S°(H2), and S°(C2H6).
Apply the formula for the standard entropy change of the reaction: ΔS°_rxn = ΣS°(products) - ΣS°(reactants).
Substitute the S° values into the formula: ΔS°_rxn = [S°(C2H6)] - [S°(C2H4) + S°(H2)].
Rationalize the sign of ΔS°_rxn by considering the change in the number of gas molecules: The reaction goes from 2 moles of gas (C2H4 and H2) to 1 mole of gas (C2H6), which typically results in a decrease in entropy (ΔS°_rxn < 0).

주요 개념

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

Entropy (ΔS)

Entropy is a measure of the disorder or randomness in a system. In chemical reactions, it reflects the number of ways the particles can be arranged. A positive ΔS indicates an increase in disorder, while a negative ΔS suggests a decrease. Understanding how the number of gas molecules changes during a reaction is crucial for predicting the sign of ΔS.
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Entropy in Thermodynamics

Standard Reaction Entropy (ΔSrxn°)

Standard reaction entropy (ΔSrxn°) is the change in entropy for a reaction under standard conditions (1 atm, 25°C). It is calculated using the standard molar entropies of the reactants and products. The formula ΔSrxn° = ΣS°(products) - ΣS°(reactants) helps quantify the change in disorder associated with the reaction, which is essential for understanding thermodynamic favorability.
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가이드 코스
03:33
Standard Molar Entropy

Molecular Complexity and Gas Behavior

The complexity of molecules and their states (gas, liquid, solid) significantly affects entropy. Gaseous molecules generally have higher entropy than liquids or solids due to their greater freedom of movement. In the reaction C2H4(g) + H2(g) → C2H6(g), the decrease in the number of gas molecules (from 2 to 1) suggests a decrease in entropy, which can help rationalize the sign of ΔSrxn°.
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가이드 코스
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Coordination Complexes Example
관련 실천
교과서 질문

Use data from Appendix IIB to calculate ΔS°rxn for each of the reactions. In each case, try to rationalize the sign of ΔS°rxn. d. 2 H2S(g) + 3 O2(g) → 2 H2O(l) + 2 SO2(g)

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Use data from Appendix IIB to calculate ΔS°rxn for each of the reactions. In each case, try to rationalize the sign of ΔS°rxn . b. C(s) + H2O(g) → CO(g) + H2(g)

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교과서 질문

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교과서 질문

Use data from Appendix IIB to calculate ΔS°rxn for each of the reactions. In each case, try to rationalize the sign of ΔS°rxn. c. CO(g) + H2O(g) → H2(g) + CO2(g)

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