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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Brown 15th EditionCh.5 - Thermochemistry문제 42c
5장, 문제 42c

Without referring to tables, predict which of the following has the higher enthalpy in each case: (c) 1 mol H2(g) and 0.5 mol O2(g) at 25 °C or 1 mol H2O(g) at 25 °C

검증된 단계별 안내
1
Identify the chemical reaction involved: H_2(g) + 0.5 O_2(g) \(\rightarrow\) H_2O(g).
Understand that the enthalpy change (\(\Delta\) H) for this reaction is related to the formation of water from hydrogen and oxygen.
Recall that the enthalpy of formation for a compound is typically negative, indicating that energy is released when the compound forms from its elements.
Consider that the reactants (H_2 and O_2) are in their elemental forms, which generally have higher enthalpy compared to the compound formed (H_2O).
Conclude that the enthalpy of the reactants (H_2 and O_2) is higher than that of the product (H_2O) because energy is released during the formation of water.

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주요 개념

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Enthalpy

Enthalpy is a thermodynamic property that represents the total heat content of a system. It is defined as the sum of the internal energy and the product of pressure and volume. Enthalpy changes are crucial for understanding heat transfer during chemical reactions, particularly in constant pressure conditions, which is common in many chemical processes.
추천 영상:
가이드 코스
02:34
Enthalpy of Formation

Standard State Conditions

Standard state conditions refer to a set of specific conditions (usually 1 atm pressure and a specified temperature, often 25 °C) under which the properties of substances are measured. These conditions allow for consistent comparisons of enthalpy values, as substances can exist in different phases (solid, liquid, gas) under varying conditions, affecting their enthalpy.
추천 영상:
가이드 코스
01:10
Standard Reduction Potentials

Phase Changes and Enthalpy of Formation

The enthalpy of formation is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. Understanding the enthalpy of formation for water and the gaseous reactants is essential for predicting which has a higher enthalpy, as phase changes (from gas to liquid or solid) significantly influence the enthalpy values due to the energy associated with breaking or forming bonds.
추천 영상:
가이드 코스
02:34
Enthalpy of Formation
관련 실천
교과서 질문

Ozone, O3(g), is a form of elemental oxygen that plays an important role in the absorption of ultraviolet radiation in the stratosphere. It decomposes to O2(g) at room temperature and pressure according to the following reaction: 2 O3(g) → 3 O2(g) ΔH= -284.6 kJ b. Which has the higher enthalpy under these conditions, 2 O3(g) or 3 O2(g)?

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교과서 질문

Consider the following reaction: 2 CH3OH(g) → 2 CH4(g) + O2(g) ΔH = +252.8 kJ (d) How many kilojoules of heat are released when 38.5 g of CH4(g) reacts completely with O2(g) to form CH3OH(g) at constant pressure?

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교과서 질문

Without referring to tables, predict which of the following has the higher enthalpy in each case: (b) 2 mol of hydrogen atoms or 1 mol of H2

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교과서 질문

Consider the following reaction: 2 CH3OH(g) → 2 CH4(g) + O2(g) ΔH = +252.8 kJ (b) Calculate the amount of heat transferred when 24.0 g of CH3OH(g) is decomposed by this reaction at constant pressure.

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교과서 질문

Without referring to tables, predict which of the following has the higher enthalpy in each case: (a) 1 mol CO2(s) or 1 mol CO2(g) at the same temperature

3
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