Chem - KMT of GAS

Expansion

gas particles move in all directions and fill the container

Fluidity

gas particles have no attractive forces so particles flow past each other

Low Density

gas particles are far apart

Compressibility

the volume of particles are negligible compared to the container and the particles are far apart

Diffusion

spontaneous (no energy required) mixing of two gases caused by random motion

Effusion

gas particles pass through a small opening

Pressure

is the result of large numbers of rapidly moving gas particles simultaneously colliding with an object

Factors affecting gas pressure

amount of gas (moles) volume and temperature

Pressure

Force/Area

Pressure Units

1 atm = 760mmHg = 760 torr = 101.3 kPa

Standard Temperature and Pressure (STP)

Temperature: 0C or 273K

Convert ot kelvin

Pressure: 1 atm or 760mmHg or 101.3kPa

Ideal Gas

follows gas laws at all conditions of pressure and temperature and would conform to the postulates of the KMT. Particles would have no volume & no attraction b/w the particles.

Real Gases

due to attractive forced it can condense to a liquid when it is compressed or cooled. Water vapor at 100C condenses to a liquid when it cools. Polar molecules attracted to each other.

no gas conforms to all the KMT

ideal gas doesn’t exist

Particles of real gases

have volume and there are attractions b/w particles

High temperatures and Low Pressure

Real Gas behaves like an ideal gas.

At high temps: particles have enough energy (KMT) to overcome attractive forces

At low pressure: particles are far apart

Real gases at High Pressure

Deviate from an ideal gas because the attractive forces reduce the distance b/w the particles and the gas occupies a smaller volume than expected

Most ideal gas Behavior

Nonpolar molecule: weakest attractive force

A gas consists of a large #s of particles with an insignificant ___ that are in constant ____

volume, motion

Each particle travels in a ____ ____ until it collides with another particle or object. The particle exerts a ____ as a result of that collision.

straight line, force

All collisions of gas particles are perfectly ___ (total kinetic energy constant).

elastic

There are no ____ forces b/w molecules of an ideal gas.

attractive

absolute temp (kelvin) is a measure of the ____

average kinetic energy

Gases at the same temp have

the same average kinetic energy

Kinetic energy: 1/2mv²

1/2(mass)(velocity)²

Ideal gas conditions

• High temp

• low pressure

• particle size small compared to space b/w particle

• Interactions b/w particles are insignificant

Nonideal gas condition

• Low temp

• high pressure

• particle size significant compared to space b/w particles

• Interactions b/w particles are significant

Constant Volume

Temp, Kinteric Energy, Pressure are all direct

Cool gas: fewer and less energetic collisions

Hot gas: more and more energetic collisions

Constant temp

Volume and Pressure are Inverse

Gas Laws

Apply to IDEAL Gases

Boyle’s Law

Pressure-Volume Relationship (constant Temp) P1V1=P2V2

Volume and Pressure are inverse

When volume increases the collision rate decreases causing pressure to decrease with constant temperature

Charles’ Law

Temperature-Volume Relationship (constant Pressure) V1/T1 = V2/T2

Temp and Volume are direct

At constant pressure and an increase in temp the collision rate increases and are the collisions are more energetic. To maintain constant gas pressure, the volume increases.

Gay-Lussac’s Law

Pressure-Temperature Relationship (constant Volume) P1/T1 = P2/T2

Temp and pressure are direct

Ina. container that has a fixed volume, an increase in temp causes the collisions to be more frequent and with more energy. Since the volume is constant the gas pressure increases.

Combined Gas Law

(P1*V1)/T1 = (P2*V2)/T2

Avogadro’s Principal

• At the SAME TEMPERATURE and PRESSURE, equal VOLUMES of gases contain the SAME # of particles.

• As the # of particles increases, the frequency of collisions with the walls of the container increases which leads to an increase in the pressure of the gas

• Flexible container will expand until the pressure of the gas inside the container once again balances the pressure of the gas outside

• Thus, Volume of the gas is proportional to the # of gas particles

Gas mixtures: Dalton’s Law of Partial Pressures

Ptotal = Pa + Pb + Pc + …

Partial Pressure is the pressure that an individual gas would exert if it were alone in the container.

Gases collected by WATER DISPLACEMENT

The KMT predicts that the pressure rises as the temp of a gas increases because___

both the gas molecules collide more frequently with the wall and the gas molecules collide more energetically with the wall

Higher Molecular speed

the lighter the molecule

The KMT does not work well for real gases at low temps because the gas molecules

have the opportunity for intermolecular attraction

T

T or F: The average kinetic energy of an ideal gas particle is proportional to the temp in Kelvin

T

T or F: The volume of ideal gas particles is negligible compared to the volume of the container

T

T or F: The ideal gas particles exert no attractive force upon each other

F

T or or F: The mass of an ideal gas is negligible

T

T or F: An ideal gas will not condense when compressed or cooled

F

T or F: The pressure decreases as the temp of a gas increases

T

T or F: Real gases deviate from ideal gas behavior because the attractions b/w gas molecules exists

F

T or F: Real gas are more like ideal gases with increasing pressure

T

T or F: Real gases are more like ideal gases with increasing temp

F

T or F: Real gas are more like idea gases with decreasing volume of the gas container

T

T or F: Ideal gas behavior is best achieved at low pressure and high temp with real gases