Textbook Question
Redraw the following diagram to represent the situation (b) when work has been lost by the system.
Ch.9 - Thermochemistry: Chemical Energy
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement170
- Ch.2 - Atoms, Molecules & Ions160
- Ch.3 - Mass Relationships in Chemical Reactions169
- Ch.4 - Reactions in Aqueous Solution199
- Ch.5 - Periodicity & Electronic Structure of Atoms102
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory92
- Ch.7 - Covalent Bonding and Electron-Dot Structures61
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure59
- Ch.9 - Thermochemistry: Chemical Energy122
- Ch.10 - Gases: Their Properties & Behavior155
- Ch.11 - Liquids & Phase Changes54
- Ch.12 - Solids and Solid-State Materials73
- Ch.13 - Solutions & Their Properties120
- Ch.14 - Chemical Kinetics98
- Ch.15 - Chemical Equilibrium125
- Ch.16 - Aqueous Equilibria: Acids & Bases110
- Ch.17 - Applications of Aqueous Equilibria147
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium86
- Ch.19 - Electrochemistry154
- Ch.20 - Nuclear Chemistry96
- Ch.21 - Transition Elements and Coordination Chemistry156
- Ch.22 - The Main Group Elements187
- Ch.23 - Organic and Biological Chemistry51
Chapter 9, Problem 35b
Imagine a reaction that results in a change in both volume and temperature:
(b) Has there been an enthalpy change? If so, what is the sign of ∆H? Is the reaction exothermic or endothermic?
Verified step by step guidance1
Step 1: Identify the initial and final states of the system. Initially, the temperature is 320 K and the pressure is 1 atm. Finally, the temperature is 370 K and the pressure remains 1 atm.
Step 2: Recognize that an increase in temperature generally indicates that heat has been absorbed by the system.
Step 3: Recall that enthalpy change (∆H) is related to the heat absorbed or released at constant pressure. Since the pressure is constant at 1 atm, we can consider the enthalpy change.
Step 4: Determine the sign of ∆H. If the system absorbs heat, ∆H is positive, indicating an endothermic reaction. If the system releases heat, ∆H is negative, indicating an exothermic reaction.
Step 5: Conclude that since the temperature increased from 320 K to 370 K, the system absorbed heat, making ∆H positive and the reaction endothermic.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enthalpy Change (∆H)
Enthalpy change (∆H) is a measure of the heat content of a system at constant pressure. It indicates whether a reaction absorbs heat (endothermic, ∆H > 0) or releases heat (exothermic, ∆H < 0). In the context of the given reaction, a change in temperature suggests that heat is either absorbed or released, which directly relates to the enthalpy change.
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Enthalpy of Formation
Exothermic vs. Endothermic Reactions
Exothermic reactions release heat to the surroundings, resulting in an increase in temperature of the surroundings, while endothermic reactions absorb heat, leading to a decrease in temperature of the surroundings. The temperature increase from 320 K to 370 K in the reaction indicates that heat is being absorbed, suggesting that the reaction is endothermic.
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02:30Endothermic & Exothermic Reactions
Ideal Gas Law and Thermodynamic Principles
The Ideal Gas Law (PV=nRT) relates pressure, volume, and temperature of a gas. In this scenario, the constant pressure (1 atm) and the change in temperature imply that the volume may also change, affecting the internal energy and enthalpy of the system. Understanding these principles helps in analyzing how energy is transferred during the reaction.
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Related Practice
Textbook Question
Redraw the following diagram to represent the situation (a) when work has been gained by the system and
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Textbook Question
Imagine a reaction that results in a change in both volume and temperature: (a) Has any work been done? If so, is its sign positive or negative?
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Textbook Question
A piece of dry ice (solid CO2) is placed inside a balloon, and the balloon is tied shut. Over time, the carbon dioxide sub- limes, causing the balloon to increase in volume. Give the sign of the enthalpy change and the sign of work for the sublima-tion of CO2.
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Textbook Question
A reaction is carried out in a cylinder fitted with a movable piston. The starting volume is V = 5.00 L, and the appa- ratus is held at constant temperature and pressure. Assum- ing that ∆H = -35.0 kJ and ∆E = -34.8 kJ, redraw the piston to show its position after reaction. Does V increase,decrease, or remain the same?