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Ch.10 - Gases
Chapter 10, Problem 79a

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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Identify the relationship between temperature and kinetic energy. According to the kinetic molecular theory, the average kinetic energy of gas molecules is directly proportional to the absolute temperature of the gas.
Convert the initial and final temperatures from Celsius to Kelvin for accurate calculations. Recall that the conversion formula is T(K) = T(°C) + 273.15.
Understand that since the volume is held constant and the temperature is increased, the pressure will change according to Gay-Lussac's Law, which states that the pressure of a gas is directly proportional to its temperature when volume is constant.
Analyze how the increase in temperature from 20 °C to 250 °C affects the kinetic energy. Since the temperature increases, the average kinetic energy of the nitrogen molecules will also increase.
Conclude that the increase in temperature results in an increase in the average kinetic energy of the nitrogen molecules, leading to faster moving particles and higher collision frequency with the walls of the container.

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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 the motion of their molecules. It states that gas molecules are in constant, random motion and that the temperature of a gas is directly proportional to the average kinetic energy of its molecules. As temperature increases, the average speed and energy of the molecules also increase, leading to greater kinetic energy.
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Temperature and Kinetic Energy Relationship

Temperature is a measure of the average kinetic energy of the particles in a substance. In gases, an increase in temperature results in an increase in the average kinetic energy of the molecules. This relationship is crucial for understanding how changes in temperature affect the motion and energy of gas molecules, particularly in a constant volume scenario.
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Constant Volume Conditions

In a constant volume scenario, the pressure of a gas will change with temperature according to Gay-Lussac's Law. While the volume remains fixed, increasing the temperature leads to an increase in the average kinetic energy of the gas molecules, which in turn increases the pressure exerted by the gas on the walls of the container. This concept is essential for predicting the behavior of gases under varying thermal conditions.
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Related Practice
Textbook Question

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. (b) The gas molecules are assumed to exert no forces on each other. (c) All the molecules of a gas at a given temperature have the same kinetic energy. (d) The volume of the gas molecules is negligible in comparison to the total volume in which the gas is contained. (e) All gas molecules move with the same speed if they are at the same temperature.

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Textbook Question
Radon (Rn) is the heaviest (and only radioactive) member ofthe noble gases. How much slower is the root-mean-squarespeed 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: (b) the rootmean-square speed of the molecules. (c) the strength of the impact of an average molecule with the container walls. (d) the total number of collisions of molecules with walls per second.

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Textbook Question

Suppose you have two 1-L flasks, one containing N2 at STP, the other containing CH4 at STP. How do these systems compare with respect to (a) number of molecules?

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Textbook Question

Suppose you have two 1-L flasks, one containing N2 at STP, the other containing CH4 at STP. How do these systems compare with respect to (b) density?

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