Skip to main content
Ch 18: Thermal Properties of Matter
Young & Freedman Calc - University Physics 15th Edition
Young & Freedman Calc15th EditionUniversity PhysicsISBN: 9780135159552Not the one you use?Change textbook
Chapter 18, Problem 41a

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}.

Verified step by step guidance
1
First, understand that the most probable speed \( v_{mp} \) for a gas molecule is given by the formula \( v_{mp} = \sqrt{\frac{2kT}{m}} \), where \( k \) is the Boltzmann constant \( (1.38 \times 10^{-23} \text{ J/K}) \), \( T \) is the temperature in Kelvin, and \( m \) is the mass of a single molecule.
Convert the molar mass of CO2 from grams per mole to kilograms per molecule. Since the molar mass is 44.0 g/mol, convert this to kg/mol by dividing by 1000, resulting in 0.044 kg/mol. Then, divide by Avogadro's number \( (6.022 \times 10^{23} \text{ molecules/mol}) \) to find the mass of a single molecule.
Substitute the values into the formula for \( v_{mp} \). Use \( T = 300 \text{ K} \) and the calculated mass of a single CO2 molecule.
Calculate the expression \( \frac{2kT}{m} \) using the values for \( k \), \( T \), and \( m \).
Finally, take the square root of the result from the previous step to find the most probable speed \( v_{mp} \).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
3m
Was this helpful?

Key Concepts

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

Maxwell-Boltzmann Distribution

The Maxwell-Boltzmann distribution describes the distribution of speeds among particles in a gas. It is crucial for understanding how the most probable speed, average speed, and root-mean-square speed are derived. The distribution is dependent on temperature and particle mass, influencing the speed of gas molecules.
Recommended video:
Guided course
07:59
Speed Distribution & Special Speeds of Ideal Gases

Most Probable Speed

The most probable speed (v_mp) is the speed at which the largest number of gas molecules are moving, according to the Maxwell-Boltzmann distribution. It is calculated using the formula v_mp = sqrt(2kT/m), where k is the Boltzmann constant, T is the temperature, and m is the mass of a molecule.
Recommended video:
Guided course
04:03
Probability Distribution Graph

Molar Mass and Molecular Mass

Molar mass is the mass of one mole of a substance, expressed in grams per mole, and is essential for converting between moles and grams. For gases, the molecular mass is used to calculate the mass of individual molecules, which is necessary for determining speeds using the Maxwell-Boltzmann distribution.
Recommended video:
Guided course
20:32
Mass Spectrometers