Domanda del libro di testo
Given the data N2(g) + O2(g) → 2 NO(g) ΔH = +180.7 kJ 2 NO(g) + O2(g) → 2 NO2(g) ΔH = -113.1 kJ 2 N2O(g) → 2 N2(g) + O2(g) ΔH = -163.2 kJ use Hess's law to calculate ΔH for the reaction N2O(g) + NO2(g) → 3 NO(g)
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Ch.5 - Thermochemistry
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232
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TOC.tableOfContents
- Ch.1 - Introduction: Matter, Energy, and Measurement177
- Ch.2 - Atoms, Molecules, and Ions231
- Ch.3 - Chemical Reactions and Reaction Stoichiometry216
- Ch.4 - Reactions in Aqueous Solution189
- Ch.5 - Thermochemistry175
- Ch.6 - Electronic Structure of Atoms168
- Ch.7 - Periodic Properties of the Elements150
- Ch.8 - Basic Concepts of Chemical Bonding177
- Ch.9 - Molecular Geometry and Bonding Theories200
- Ch.10 - Gases179
- Ch.11 - Liquids and Intermolecular Forces113
- Ch.12 - Solids and Modern Materials154
- Ch.13 - Properties of Solutions157
- Ch.14 - Chemical Kinetics199
- Ch.15 - Chemical Equilibrium128
- Ch.16 - Acid-Base Equilibria164
- Ch.17 - Additional Aspects of Aqueous Equilibria163
- Ch.18 - Chemistry of the Environment105
- Ch.19 - Chemical Thermodynamics164
- Ch.20 - Electrochemistry171
- Ch.21 - Nuclear Chemistry122
- Ch.22 - Chemistry of the Nonmetals82
- Ch.23 - Transition Metals and Coordination Chemistry79
- Ch.24 - The Chemistry of Life: Organic and Biological Chemistry16
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 65
From the enthalpies of reaction H2(g) + F2(g) → 2 HF(g) ΔH = -537 kJ C(s) + 2 F2(g) → CF4(g) ΔH = -680 kJ 2 C(s) + 2 H2(g) → C2H4(g) ΔH = +52.3 kJ Calculate H for the reaction of ethylene with F2: C2H4(g) + 6 F2(g) → 2 CF4(g) + 4 HF(g)
Guida verificata passo dopo passo1
Identify the target reaction: \( \text{C}_2\text{H}_4(g) + 6 \text{F}_2(g) \rightarrow 2 \text{CF}_4(g) + 4 \text{HF}(g) \).
Use Hess's Law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for each step of the reaction.
Write the given reactions and their enthalpy changes: \( \text{H}_2(g) + \text{F}_2(g) \rightarrow 2 \text{HF}(g) \), \( \Delta H = -537 \text{ kJ} \); \( \text{C}(s) + 2 \text{F}_2(g) \rightarrow \text{CF}_4(g) \), \( \Delta H = -680 \text{ kJ} \); \( 2 \text{C}(s) + 2 \text{H}_2(g) \rightarrow \text{C}_2\text{H}_4(g) \), \( \Delta H = +52.3 \text{ kJ} \).
Manipulate the given reactions to match the target reaction: Reverse the third reaction to form \( \text{C}_2\text{H}_4(g) \) as a reactant, which changes its \( \Delta H \) to \( -52.3 \text{ kJ} \).
Add the enthalpy changes of the manipulated reactions to find the total \( \Delta H \) for the target reaction.
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Enthalpy of Reaction
Enthalpy of reaction (ΔH) is the heat change associated with a chemical reaction at constant pressure. It indicates whether a reaction is exothermic (releases heat, ΔH < 0) or endothermic (absorbs heat, ΔH > 0). Understanding ΔH is crucial for predicting the energy changes during reactions and for applying Hess's law to calculate enthalpy changes for complex reactions.
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02:34
Enthalpy of Formation
Hess's Law
Hess's Law states that the total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps, regardless of the pathway taken. This principle allows chemists to calculate the enthalpy change for a reaction that may be difficult to measure directly by using known enthalpy changes of related reactions. It is particularly useful in multi-step reactions, like the one presented in the question.
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02:03Hess's Law
Stoichiometry
Stoichiometry involves the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It provides the ratios in which substances react and form products, which is essential for determining the enthalpy changes in reactions. In the context of the question, stoichiometry helps in relating the amounts of C2H4 and F2 to the products CF4 and HF, allowing for accurate enthalpy calculations.
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01:16Stoichiometry Concept
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(a) Why does the standard enthalpy of formation of both the very reactive fluorine (F2) and the almost inert gas nitrogen (N2) both read zero?
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Consider the following hypothetical reactions: A → B ΔHI = +60 kJ B → C ΔHII = -90 kJ (b) Construct an enthalpy diagram for substances A, B, and C, and show how Hess's law applies.
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Calculate the enthalpy change for the reaction P4O6(s) + 2 O2(g) → P4O10(s) given the following enthalpies of reaction: P4(s) + 3 O2(g) → P4O6(s) ΔH = -1640.1 kJ P4(s) + 5 O2(g) → P4O10(s) ΔH = -2940.1 kJ
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Domanda del libro di testo
(c) What is meant by the term standard enthalpy of formation?
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Domanda del libro di testo
From the enthalpies of reaction 2 C(s) + O2(g) → 2 CO(g) ΔH = -221.0 kJ 2 C(s) + O2(g) + 4 H2(g) → 2 CH3OH(g) ΔH = -402.4 kJ Calculate ΔH for the reaction CO(g) + 2 H2(g) → CH3OH(g)
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