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Ch.6 - Thermochemistry
Chapter 6, Problem 38

During an energy exchange, a chemical system absorbs energy from its surroundings. What is the sign of ΔEsys for this process?

Verified step by step guidance
1
Identify the type of process: The problem states that the chemical system absorbs energy from its surroundings, which indicates an endothermic process.
Understand the concept of energy exchange: In an endothermic process, energy is absorbed by the system, meaning the system gains energy.
Determine the sign of \( \Delta E_{\text{sys}} \): Since the system is gaining energy, the change in energy of the system (\( \Delta E_{\text{sys}} \)) is positive.
Relate to the first law of thermodynamics: The first law states that energy cannot be created or destroyed, only transferred. Here, energy is transferred into the system, increasing its internal energy.
Conclude the sign of \( \Delta E_{\text{sys}} \): Therefore, the sign of \( \Delta E_{\text{sys}} \) is positive, indicating an increase in the system's energy.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Energy Exchange

Energy exchange in a chemical system refers to the transfer of energy between the system and its surroundings. This can occur in the form of heat or work, and it is crucial to understand how energy flows to determine the changes in the system's internal energy.
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Internal Energy (ΔEsys)

The internal energy of a system, denoted as ΔEsys, represents the total energy contained within the system, including kinetic and potential energy of its particles. When a system absorbs energy, its internal energy increases, leading to a positive value for ΔEsys.
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Sign Convention in Thermodynamics

In thermodynamics, a sign convention is used to indicate the direction of energy transfer. If a system absorbs energy, it is considered positive, while energy released to the surroundings is negative. Thus, for a system absorbing energy, ΔEsys is positive.
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Related Practice
Open Question

A particular frost-free refrigerator uses about 745 kWh of electrical energy per year. Express this amount of energy in each unit. a. J b. kJ

Textbook Question

A particular frost-free refrigerator uses about 745 kWh of electrical energy per year. Express this amount of energy in each unit. c. Cal

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Textbook Question

Which statement is true of the internal energy of a system and its surroundings during an energy exchange with a negative ΔEsys? a. The internal energy of the system increases and the internal energy of the surroundings decreases. b. The internal energy of both the system and the surroundings increases. c. The internal energy of both the system and the surroundings decreases. d. The internal energy of the system decreases and the internal energy of the surroundings increases.

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Textbook Question

Identify each energy exchange as primarily heat or work and determine whether the sign of ΔE is positive or negative for the system. a. Sweat evaporates from skin, cooling the skin. (The evaporating sweat is the system.)

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Textbook Question

Identify each energy exchange as primarily heat or work and determine whether the sign of ΔE is positive or negative for the system. a. Sweat evaporates from skin, cooling the skin. (The evaporating sweat is the system.) b. A balloon expands against an external pressure. (The contents of the balloon is the system.) c. An aqueous chemical reaction mixture is warmed with an external flame. (The reaction mixture is the system.) Identify energy exchanges as primarily heat or work. Determine whether the sign of E is positive or negative for the system.

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Textbook Question

Identify each energy exchange as primarily heat or work and determine whether the sign of ΔE is positive or negative for the system. Identify each energy exchange as primarily heat or work. a. A rolling billiard ball collides with another billiard ball. The first billiard ball (defined as the system) stops rolling after the collision. b. A book falls to the floor. (The book is the system). c. A father pushes his daughter on a swing. (The daughter and the swing are the system). Identify each energy exchange as primarily heat or work.

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