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Ch 18: Thermal Properties of Matter
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 18, Problem 41c

For diatomic carbon dioxide gas (CO2, molar mass 44.044.0 g/mol) at T=300T = 300 K, calculate the root-mean-square speed vrmsv_{rms}.

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First, understand the concept of root-mean-square speed (v_rms). It is a measure of the average speed of particles in a gas and is derived from the kinetic theory of gases.
The formula for root-mean-square speed is given by: 3kTm, where k is the Boltzmann constant (1.38×10¯23 J K¯1), T is the temperature in Kelvin, and m is the mass of one molecule in kilograms.
Convert the molar mass of CO2 from grams per mole to kilograms per molecule. Use the conversion factor: 1 mol = 6.022×10¯23 molecules.
Calculate the mass of one CO2 molecule using the formula: molar massAvogadro number. This will give you the mass in kilograms.
Substitute the values for k, T, and m into the v_rms formula to find the root-mean-square speed of CO2 at 300 K.

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Key Concepts

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

Root-Mean-Square Speed

The root-mean-square speed (v_rms) is a measure of the average speed of particles in a gas, derived from the kinetic theory of gases. It is calculated using the formula v_rms = sqrt((3kT)/m), where k is the Boltzmann constant, T is the temperature in Kelvin, and m is the mass of a single molecule. This concept helps understand the distribution of molecular speeds in a gas.
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Kinetic Theory of Gases

The kinetic theory of gases explains the macroscopic properties of gases by considering their molecular composition and motion. It assumes that gas molecules are in constant, random motion and that their collisions are perfectly elastic. This theory provides the basis for calculating properties like pressure, temperature, and speed, including the root-mean-square speed.
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Molar Mass and Molecular Mass

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol), and is crucial for converting between moles and grams. Molecular mass refers to the mass of a single molecule, typically expressed in atomic mass units (amu). For calculations involving gases, knowing the molar mass allows us to determine the mass of individual molecules, which is essential for computing the root-mean-square speed.
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Related Practice
Textbook Question

The vapor pressure is the pressure of the vapor phase of a substance when it is in equilibrium with the solid or liquid phase of the substance. The relative humidity is the partial pressure of water vapor in the air divided by the vapor pressure of water at that same temperature, expressed as a percentage. The air is saturated when the humidity is 100%100\%. The vapor pressure of water at 20.020.0°C is 2.34×1032.34\(\times\)10^3 Pa. If the air temperature is 20.020.0°C and the relative humidity is 60%60\%, what is the partial pressure of water vapor in the atmosphere (that is, the pressure due to water vapor alone)?

Textbook Question

Solid water (ice) is slowly warmed from a very low temperature. What minimum external pressure p1p_1 must be applied to the solid if a melting phase transition is to be observed? Describe the sequence of phase transitions that occur if the applied pressure pp is such that p<p1p<p_1.

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Textbook Question

For diatomic carbon dioxide gas (CO2, molar mass 44.044.0 g/mol) at T=300T = 300 K, calculate the most probable speed vmpv_{mp}.

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Textbook Question

For diatomic carbon dioxide gas (CO2, molar mass 44.044.0 g/mol) at T=300T = 300 K, calculate the average speed vavv_{av}.

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Textbook Question

Compute the specific heat at constant volume of nitrogen (N2) gas, and compare it with the specific heat of liquid water. The molar mass of N2 is 28.028.0 g/mol.

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Textbook Question

For a gas of nitrogen molecules (N2), what must the temperature be if 94.7%94.7\% of all the molecules have speeds less than 15001500 m/s? Use Table 18.218.2. The molar mass of N2 is 28.028.0 g/mol.

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