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Ch.11 - Liquids & Phase Changes
McMurry - Chemistry 8th Edition
McMurry8th EditionChemistryISBN: 9781292336145당신이 사용하는 게 아니라요?교과서 변경
11장, 문제 40

Naphthalene, better known as 'mothballs,' has bp = 218 °C and ΔHvap = 43.3 kJ>mol. What is the entropy of vaporization, ΔSvap in J/(K mol) for naphthalene?

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Identify the given values: boiling point (T) = 218 °C, which needs to be converted to Kelvin by adding 273.15, and the enthalpy of vaporization (ΔHvap) = 43.3 kJ/mol, which needs to be converted to Joules by multiplying by 1000.
Convert the boiling point from Celsius to Kelvin: T(K) = 218 °C + 273.15.
Convert the enthalpy of vaporization from kJ/mol to J/mol: ΔHvap(J/mol) = 43.3 kJ/mol × 1000 J/kJ.
Use the thermodynamic equation for entropy of vaporization: ΔSvap = ΔHvap / T.
Substitute the values of ΔHvap and T into the equation to calculate ΔSvap.

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주요 개념

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

Entropy of Vaporization (ΔS<sub>vap</sub>)

The entropy of vaporization is a thermodynamic quantity that measures the change in entropy when a substance transitions from a liquid to a vapor. It reflects the degree of disorder in the system; a higher ΔS<sub>vap</sub> indicates greater disorder in the gaseous state compared to the liquid state. This concept is crucial for understanding how temperature and energy changes affect phase transitions.
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Entropy and Physical Changes Example

Gibbs Free Energy and Phase Changes

Gibbs Free Energy (G) is a thermodynamic potential that helps predict the direction of chemical reactions and phase changes. The relationship between Gibbs Free Energy, enthalpy (ΔH), and entropy (ΔS) is given by the equation ΔG = ΔH - TΔS. For a phase change at equilibrium, ΔG is zero, allowing us to relate ΔH and ΔS to calculate the entropy of vaporization.
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가이드 코스
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Gibbs Free Energy of Reactions

Clausius-Clapeyron Equation

The Clausius-Clapeyron equation describes the relationship between the vapor pressure of a substance and its temperature, providing a way to calculate the entropy of vaporization. It states that the slope of the vapor pressure curve is proportional to the enthalpy of vaporization divided by the temperature. This equation is essential for understanding how changes in temperature affect the vaporization process and the associated entropy changes.
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가이드 코스
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Clausius-Clapeyron Equation