Domanda del libro di testo
Consider the following hypothetical reactions: A → B ΔHI = +60 kJ B → C ΔHII = -90 kJ (a) Use Hess’s law to calculate the enthalpy change for the reaction A → C.
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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 62b
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.
Guida verificata passo dopo passo1
Identify the enthalpy changes for each reaction: \( \Delta H_{I} = +60 \text{kJ} \) for \( A \rightarrow B \) and \( \Delta H_{II} = -90 \text{kJ} \) for \( B \rightarrow C \).
Draw an enthalpy diagram with the y-axis representing enthalpy (H) and the x-axis representing the reaction progress.
Place substance A at the starting point on the y-axis. Since \( \Delta H_{I} = +60 \text{kJ} \), draw an upward arrow to represent the conversion of A to B, indicating an increase in enthalpy.
From B, draw a downward arrow to represent the conversion of B to C, since \( \Delta H_{II} = -90 \text{kJ} \), indicating a decrease in enthalpy.
Apply Hess's Law by adding the enthalpy changes of the two steps to find the overall enthalpy change for the reaction \( A \rightarrow C \).
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Enthalpy (ΔH)
Enthalpy is a thermodynamic quantity that represents the total heat content of a system. It is often expressed in kilojoules (kJ) and can indicate whether a reaction is exothermic (releases heat, ΔH < 0) or endothermic (absorbs heat, ΔH > 0). In the given reactions, the positive and negative values of ΔH indicate the heat changes associated with the transformations between substances A, B, and C.
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Percorso guidato
02:34
Enthalpy of Formation
Hess's Law
Hess's Law states that the total enthalpy change for a chemical reaction is the same, regardless of the number of steps taken to achieve the reaction. This principle allows us to calculate the enthalpy change for a reaction by summing the enthalpy changes of individual steps, making it useful for constructing enthalpy diagrams and understanding the overall energy changes in a series of reactions.
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02:03Hess's Law
Enthalpy Diagram
An enthalpy diagram visually represents the enthalpy changes of reactants and products in a chemical reaction. It typically shows the relative energy levels of the substances involved, allowing for a clear understanding of how energy is absorbed or released during the reaction process. In this case, the diagram would illustrate the transitions from A to B and then from B to C, highlighting the respective enthalpy changes.
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Percorso guidato
02:34Enthalpy of Formation
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