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Ch.10 - Gases
Chapter 10, Problem 76a

Indicate which of the following statements regarding the kinetic-molecular theory of gases are correct. (a) The average kinetic energy of a collection of gas molecules at a given temperature is proportional to m1>2.

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Identify the key terms in the statement: 'average kinetic energy' and 'proportional to m1>2'.
Recall the kinetic-molecular theory of gases, which states that the average kinetic energy of gas molecules is directly proportional to the absolute temperature of the gas.
Understand that the average kinetic energy of gas molecules is given by the equation \( KE_{avg} = \frac{3}{2}kT \), where \( k \) is the Boltzmann constant and \( T \) is the temperature in Kelvin.
Analyze the statement 'proportional to m1>2'. This seems to suggest a dependence on mass, which is incorrect according to the kinetic-molecular theory. The theory states that kinetic energy depends on temperature, not mass.
Conclude that the statement is incorrect as it misrepresents the dependence of kinetic energy on mass rather than temperature.

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Key Concepts

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

Kinetic-Molecular Theory

The kinetic-molecular theory explains the behavior of gases in terms of particles in constant motion. It posits that gas molecules are in continuous, random motion and that their collisions with each other and the walls of their container are elastic. This theory helps to understand properties such as pressure, temperature, and volume in gases.
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Average Kinetic Energy

The average kinetic energy of gas molecules is directly related to the temperature of the gas. According to the kinetic-molecular theory, as the temperature increases, the average kinetic energy of the molecules also increases. This relationship is expressed mathematically as KE = (3/2)kT, where k is the Boltzmann constant and T is the temperature in Kelvin.
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Proportional Relationships

In the context of the kinetic-molecular theory, the average kinetic energy is proportional to the absolute temperature of the gas, not to the mass of the molecules squared. This means that while the kinetic energy depends on temperature, it does not directly depend on the mass of the gas molecules, which is a common misconception.
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Related Practice
Textbook Question
A quantity of N2 gas originally held at 531.96 kPa pressure in a 1.00-L container at 26 °C is transferred to a 12.5-L container at 20 °C. A quantity of O2 gas originally at 531.96 kPa and 26 °C in a 5.00-L container is transferred to this same container. What is the total pressure in the new container?
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Textbook Question

A sample of 3.00 g of SO21g2 originally in a 5.00-L vessel at 21 °C is transferred to a 10.0-L vessel at 26 °C. A sample of 2.35 g of N21g2 originally in a 2.50-L vessel at 20 °C is transferred to this same 10.0-L vessel. (a) What is the partial pressure of SO21g2 in the larger container?

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Textbook Question

Determine whether each of the following changes will increase, decrease, or not affect the rate with which gas molecules collide with the walls of their container: (a) increasing the volume of the container (b) increasing the temperature (c) increasing the molar mass of the gas

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Textbook Question
Radon (Rn) is the heaviest (and only radioactive) member of the noble gases. How much slower is the root-mean-square speed of Rn than He at 300 K?
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Textbook Question

You have an evacuated container of fixed volume and known mass and introduce a known mass of a gas sample. Measuring the pressure at constant temperature over time, you are surprised to see it slowly dropping. You measure the mass of the gas-filled container and find that the mass is what it should be—gas plus container—and the mass does not change over time, so you do not have a leak. Suggest an explanation for your observations.

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Textbook Question

The temperature of a 5.00-L container of N2 gas is increased from 20 °C to 250 °C. If the volume is held constant, predict qualitatively how this change affects the following: (a) the average kinetic energy of the molecules.

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