Ch.19 - Chemical Thermodynamics

Problem 15a

Chapter 19, Problem 15a

Consider the vaporization of liquid water to steam at a pressure of 1 atm. (a) Is this process endothermic or exothermic?

Verified step by step guidance

Identify the process: Vaporization is the phase transition from liquid to gas.

Recall the energy requirement: Vaporization requires energy input to overcome intermolecular forces.

Determine the type of process: Since energy is absorbed from the surroundings, the process is endothermic.

Consider the system and surroundings: In an endothermic process, the system absorbs heat, causing the surroundings to cool down.

Conclude: The vaporization of liquid water to steam at 1 atm is an endothermic process.

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Key Concepts

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

Endothermic and Exothermic Processes

Endothermic processes absorb heat from the surroundings, resulting in a temperature decrease in the environment. In contrast, exothermic processes release heat, causing an increase in the surrounding temperature. Understanding these definitions is crucial for determining the nature of a phase change, such as vaporization.

Phase Changes

Phase changes refer to the transitions between different states of matter, such as solid, liquid, and gas. Vaporization, specifically, is the transition from liquid to gas, which requires energy input to overcome intermolecular forces. Recognizing the energy dynamics involved in phase changes helps in identifying whether they are endothermic or exothermic.

Latent Heat of Vaporization

The latent heat of vaporization is the amount of energy required to convert a unit mass of a liquid into vapor without a change in temperature. For water, this process at 1 atm pressure requires significant energy input, indicating that vaporization is an endothermic process. This concept is essential for understanding the energy requirements during phase transitions.

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Related Practice

Textbook Question

Which of the following processes are spontaneous?

a. the melting of ice cubes at −10 °C and 1 atm pressure

b. separating a mixture of N₂ and O₂ into two separate samples, one that is pure N₂ and one that is pure O₂

c. alignment of iron filings in a magnetic field

d. the reaction of hydrogen gas with oxygen gas to form water vapor at room temperature

e. the dissolution of HCl(g) in water to form concentrated hydrochloric acid

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Textbook Question

Indicate whether each statement is true or false. (a) A reaction that is spontaneous in one direction will be nonspontaneous in the reverse direction under the same reaction conditions. (b) All spontaneous processes are fast. (c) Most spontaneous processes are reversible. (d) An isothermal process is one in which the system loses no heat. (e) The maximum amount of work can be accomplished by an irreversible process rather than a reversible one.

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Textbook Question

(d) Does the amount of work that a system can do on its surroundings depend on the path of the process?

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Textbook Question

Consider the vaporization of liquid water to steam at a pressure of 1 atm. (b) In what temperature range is it a spontaneous process?

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Textbook Question

Consider the vaporization of liquid water to steam at a pressure of 1 atm. (c) In what temperature range is it a nonspontaneous process?

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Textbook Question

Consider the vaporization of liquid water to steam at a pressure of 1 atm. (d) At what temperature are the two phases in equilibrium?

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