<< Chapter < Page Chapter >> Page >

What is the average kinetic energy of a nitrogen molecule (N 2 ) if its rms speed is 560 m/s? At what temperature is this rms speed achieved?

(a) 7.29 × 10 -21 J; (b) 352K or 79ºC

Got questions? Get instant answers now!

What will be the ratio of kinetic energies and rms speeds of a nitrogen molecule and a helium atom at the same temperature?

Got questions? Get instant answers now!

Section summary

  • Kinetic theory is the atomistic description of gases as well as liquids and solids.
  • Kinetic theory models the properties of matter in terms of continuous random motion of atoms and molecules.
  • The ideal gas law can also be expressed as
    PV = 1 3 Nm v 2 ¯ , size 12{ ital "PV"= { {1} over {3} } ital "Nm" {overline {v rSup { size 8{2} } }} ,} {}
    where P size 12{P} {} is the pressure (average force per unit area), V size 12{V} {} is the volume of gas in the container, N size 12{N} {} is the number of molecules in the container, m size 12{m} {} is the mass of a molecule, and v 2 ¯ size 12{ {overline {v rSup { size 8{2} } }} } {} is the average of the molecular speed squared.
  • Thermal energy is defined to be the average translational kinetic energy KE ¯ size 12{ {overline {"KE"}} } {} of an atom or molecule.
  • The temperature of gases is proportional to the average translational kinetic energy of atoms and molecules.
    KE ¯ = 1 2 m v 2 ¯ = 3 2 kT size 12{ {overline {"KE"}} = { {1} over {2} } m {overline {v rSup { size 8{2} } }} = { {3} over {2} } ital "kT"} {}

    or

    v 2 ¯ = v rms = 3 kT m . size 12{ sqrt { {overline {v rSup { size 8{2} } }} } =v rSub { size 8{"rms"} } = sqrt { { {3 ital "kT"} over {m} } } "." } {}
  • The motion of individual molecules in a gas is random in magnitude and direction. However, a gas of many molecules has a predictable distribution of molecular speeds, known as the Maxwell-Boltzmann distribution .

Conceptual questions

How is momentum related to the pressure exerted by a gas? Explain on the atomic and molecular level, considering the behavior of atoms and molecules.

Got questions? Get instant answers now!

Problems&Exercises

Some incandescent light bulbs are filled with argon gas. What is v rms size 12{v rSub { size 8{"rms"} } } {} for argon atoms near the filament, assuming their temperature is 2500 K?

1 . 25 × 10 3 m/s size 12{ size 11{1 "." "25" times "10" rSup { size 8{3} } `"m/s"}} {}

Got questions? Get instant answers now!

Average atomic and molecular speeds ( v rms ) size 12{ \( v rSub { size 8{"rms"} } \) } {} are large, even at low temperatures. What is v rms size 12{v rSub { size 8{"rms"} } } {} for helium atoms at 5.00 K, just one degree above helium’s liquefaction temperature?

Got questions? Get instant answers now!

(a) What is the average kinetic energy in joules of hydrogen atoms on the 5500 º C size 12{"5500"°C} {} surface of the Sun? (b) What is the average kinetic energy of helium atoms in a region of the solar corona where the temperature is 6 . 00 × 10 5 K size 12{6 "." "00"´"10" rSup { size 8{5} } " K"} {} ?

(a) 1 . 20 × 10 19 J size 12{ size 11{1 "." "20" times "10" rSup { size 8{ - "19"} } `J}} {}

(b) 1 . 24 × 10 17 J size 12{ size 11{1 "." "24" times "10" rSup { size 8{ - "17"} } `J}} {}

Got questions? Get instant answers now!

The escape velocity of any object from Earth is 11.2 km/s. (a) Express this speed in m/s and km/h. (b) At what temperature would oxygen molecules (molecular mass is equal to 32.0 g/mol) have an average velocity v rms size 12{v rSub { size 8{"rms"} } } {} equal to Earth’s escape velocity of 11.1 km/s?

Got questions? Get instant answers now!

The escape velocity from the Moon is much smaller than from Earth and is only 2.38 km/s. At what temperature would hydrogen molecules (molecular mass is equal to 2.016 g/mol) have an average velocity v rms size 12{v rSub { size 8{"rms"} } } {} equal to the Moon’s escape velocity?

458 K size 12{ size 11{"458"`K}} {}

Got questions? Get instant answers now!

Nuclear fusion, the energy source of the Sun, hydrogen bombs, and fusion reactors, occurs much more readily when the average kinetic energy of the atoms is high—that is, at high temperatures. Suppose you want the atoms in your fusion experiment to have average kinetic energies of 6 . 40 × 10 14 J size 12{6 "." "40"´"10" rSup { size 8{ +- "14"} } " J"} {} . What temperature is needed?

Got questions? Get instant answers now!

Suppose that the average velocity ( v rms ) size 12{ \( v rSub { size 8{"rms"} } \) } {} of carbon dioxide molecules (molecular mass is equal to 44.0 g/mol) in a flame is found to be 1 . 05 × 10 5 m/s size 12{1 "." "05"´"10" rSup { size 8{5} } " m/s"} {} . What temperature does this represent?

1 . 95 × 10 7 K size 12{ size 11{1 "." "95" times "10" rSup { size 8{7} } `K}} {}

Got questions? Get instant answers now!

Hydrogen molecules (molecular mass is equal to 2.016 g/mol) have an average velocity v rms size 12{v rSub { size 8{"rms"} } } {} equal to 193 m/s. What is the temperature?

Got questions? Get instant answers now!

Much of the gas near the Sun is atomic hydrogen. Its temperature would have to be 1 . 5 × 10 7 K size 12{1 "." 5´"10" rSup { size 8{7} } " K"} {} for the average velocity v rms size 12{v rSub { size 8{"rms"} } } {} to equal the escape velocity from the Sun. What is that velocity?

6 . 09 × 10 5 m/s size 12{ size 11{6 "." "09" times "10" rSup { size 8{5} } `"m/s"}} {}

Got questions? Get instant answers now!

There are two important isotopes of uranium— 235 U size 12{ {} rSup { size 8{"235"} } U} {} and 238 U size 12{ {} rSup { size 8{"238"} } U} {} ; these isotopes are nearly identical chemically but have different atomic masses. Only 235 U size 12{ {} rSup { size 8{"235"} } U} {} is very useful in nuclear reactors. One of the techniques for separating them (gas diffusion) is based on the different average velocities v rms size 12{v rSub { size 8{"rms"} } } {} of uranium hexafluoride gas, UF 6 size 12{"UF" rSub { size 8{6} } } {} . (a) The molecular masses for 235 U size 12{ {} rSup { size 8{"235"} } U} {} UF 6 size 12{"UF" rSub { size 8{6} } } {} and 238 U size 12{ {} rSup { size 8{"238"} } U} {} UF 6 size 12{"UF" rSub { size 8{6} } } {} are 349.0 g/mol and 352.0 g/mol, respectively. What is the ratio of their average velocities? (b) At what temperature would their average velocities differ by 1.00 m/s? (c) Do your answers in this problem imply that this technique may be difficult?

Got questions? Get instant answers now!

Questions & Answers

differentiate between demand and supply giving examples
Lambiv Reply
differentiated between demand and supply using examples
Lambiv
what is labour ?
Lambiv
how will I do?
Venny Reply
how is the graph works?I don't fully understand
Rezat Reply
information
Eliyee
devaluation
Eliyee
t
WARKISA
hi guys good evening to all
Lambiv
multiple choice question
Aster Reply
appreciation
Eliyee
explain perfect market
Lindiwe Reply
In economics, a perfect market refers to a theoretical construct where all participants have perfect information, goods are homogenous, there are no barriers to entry or exit, and prices are determined solely by supply and demand. It's an idealized model used for analysis,
Ezea
What is ceteris paribus?
Shukri Reply
other things being equal
AI-Robot
When MP₁ becomes negative, TP start to decline. Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of lab
Kelo
Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of labour (APL) and marginal product of labour (MPL)
Kelo
yes,thank you
Shukri
Can I ask you other question?
Shukri
what is monopoly mean?
Habtamu Reply
What is different between quantity demand and demand?
Shukri Reply
Quantity demanded refers to the specific amount of a good or service that consumers are willing and able to purchase at a give price and within a specific time period. Demand, on the other hand, is a broader concept that encompasses the entire relationship between price and quantity demanded
Ezea
ok
Shukri
how do you save a country economic situation when it's falling apart
Lilia Reply
what is the difference between economic growth and development
Fiker Reply
Economic growth as an increase in the production and consumption of goods and services within an economy.but Economic development as a broader concept that encompasses not only economic growth but also social & human well being.
Shukri
production function means
Jabir
What do you think is more important to focus on when considering inequality ?
Abdisa Reply
any question about economics?
Awais Reply
sir...I just want to ask one question... Define the term contract curve? if you are free please help me to find this answer 🙏
Asui
it is a curve that we get after connecting the pareto optimal combinations of two consumers after their mutually beneficial trade offs
Awais
thank you so much 👍 sir
Asui
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities, where neither p
Cornelius
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities,
Cornelius
Suppose a consumer consuming two commodities X and Y has The following utility function u=X0.4 Y0.6. If the price of the X and Y are 2 and 3 respectively and income Constraint is birr 50. A,Calculate quantities of x and y which maximize utility. B,Calculate value of Lagrange multiplier. C,Calculate quantities of X and Y consumed with a given price. D,alculate optimum level of output .
Feyisa Reply
Answer
Feyisa
c
Jabir
the market for lemon has 10 potential consumers, each having an individual demand curve p=101-10Qi, where p is price in dollar's per cup and Qi is the number of cups demanded per week by the i th consumer.Find the market demand curve using algebra. Draw an individual demand curve and the market dema
Gsbwnw Reply
suppose the production function is given by ( L, K)=L¼K¾.assuming capital is fixed find APL and MPL. consider the following short run production function:Q=6L²-0.4L³ a) find the value of L that maximizes output b)find the value of L that maximizes marginal product
Abdureman
types of unemployment
Yomi Reply
What is the difference between perfect competition and monopolistic competition?
Mohammed
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 1

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'College physics for ap® courses' conversation and receive update notifications?

Ask