CHEMISTRY CHAPTER 10 GASES

average kinetic energy

(how fast particles move) is proportional to the Kelvin temperature

RMS

-RMS average velocity increases with increasing T and with decreasing molar mass -the RMS average velocity increases with increasing T

Gases

-least dense state of matter -have indefinite shape -can expand or compress -condense to liquid when chilled ( P high, T low)

main tenets of kinetic-molecular theory

1) gases consists of large numbers of molecules that are in continuous, random motion. 2) the combined volume of all the molecules of the gas is negligible relative to the total volume in which the gas is contained. 3) attractive and repulsive forces between gas molecules are negligible

What volume is occupied by 1.00 mol of an ideal gas at 1.00 atm and 0.00°C?

22.4 L

11 elements are gases at room temperature and atomospheric pressure:

Monoatomic: He, Ne, Ar, Kr, Xe, Rn Diatomic: H2, N2, O2, F2, Cl2

Which of the following gases will effuse through a hole in a balloon fastest? Kr NO N2O NO2 Ar

NO

Boyle's Law Equation

P1V1=P2V2

Which statement A-D below is not true of an ideal gas? A.The size of the molecules is negligible. B.Molecules do not interact with each other except when they collide. C.Gas pressure is caused by collisions of the molecules with the walls of a container. D.An ideal gas mixes completely with other gases. E.Statements A-D all describe an ideal gas.

Statements A-D all describe an ideal gas.

Which of the following is unimportant when using the ideal gas law? The chemical identity of the gas sample. The temperature of the gas sample. The pressure of the gas sample. The volume of the container holding the gas sample. The amount of gas.

The chemical identity of the gas sample.

Which statement about the properties of a gas is not correct? Unlike a solid or a liquid, gases expand to occupy the entire volume of their container. When the temperature is changed, the volume of gas changes much more than the volume of a solid or liquid. Different gases are completely miscible with each other. The density of a gas typically is much larger than the density of a solid or liquid. When the pressure is changed, the volume of a gas changes much more than the volume of a solid or liquid.

The density of a gas typically is much larger than the density of a solid or liquid.

Which one of the following statements is not correct? An increase in temperature causes an increase in pressure of a gas because the frequency of molecules colliding with the walls of the container increases. An increase in temperature causes an increase in pressure of a gas because the average force exerted by molecules colliding with the walls of the container increases. All gases behave like an ideal gas at sufficiently low pressure and high temperature. The ratio PV/nRT for a real gas can be less than 1 because of attractive forces between molecules. The pressure exerted by oxygen molecules is greater than the pressure exerted by nitrogen molecules in a balloon filled with air because oxygen molecules are heavier.

The pressure exerted by oxygen molecules is greater than the pressure exerted by nitrogen molecules in a balloon filled with air because oxygen molecules are heavier.

Which one of the following statements about the properties of gases is not correct? At low temperatures, the attractive forces between molecules cause a real gas to deviate from ideal gas behavior. At high pressures, the finite size of the molecules causes a real gas to deviate from ideal gas behavior. The ratio PV/RT = 1 for one mole of an ideal gas. The ratio PV/nRT < 1 because of repulsive interactions between the molecules. The ratio PV/nRT > 1 because of the finite size of the molecules.

The ratio PV/nRT < 1 because of repulsive interactions between the molecules.

Charles law equation

V1/T1=V2/T2

Avogadro's Law Equation

V1/n1=V2/n2

the ideal gas law is based on three other gas laws:

avogadro's, boyle's and charle's laws

why did we choose average velociy

because not every gas particle moves at the same velocity at a given temperature -the distribution of speeds follows a statistical pattern called a boltzman distribution -method choice is called the root-mean-square (RMS) method, where the rms average velocity, u rms, is the square root of the average of the sum of the squares of all the molecule velocities

how is the ideal gas law formed

by combining avogadro, boyle, and charles law

Pressure

combined effect of all molecules hitting on the surface of container

kinetic molecular theory

describes how the behavior of individual gas atoms or molecules influences the overall behavior of the gas sample 1. gases consist of tiny particles (atoms or molecules), which are very small in comparison to the distances between them. 2.the particles are in constant random motion, colliding with each other. Collisions with the container create pressure. 3. the average kinetic energy (how fast the particles move) is proportional to the Kelvin temperature of the gas sample

real gases

differ from ideal gases in the following ways: -real molecules are not points- they have size - there are attractive forces between molecules

dalton's law of partial pressures

for a mixture of gases, the toal pressure exerted is the sum of partial pressures of the gases present.

thomas graham law of effusion

for two different gases at the same temperature, the ratio of their rates of effusion is given by the following equation

A ____ uniformly fills any container, is easily compressed, mixes completely with other gases, and exerts pressure of its surroundings.

gas

what is the pressure of a gas? what originates this property?

gas molecules are constantly in motion. As they strike against surfaces, they cause a push or force on that surface. pressure=force per unit area p=F/A

so what happens at high pressure and low temperature?

high pressure--> volume is larger than predicted low temperature --> pressure is smaller than predicted

The atmospheric pressure is reported to be 31.5 in of mercury. The prevailing weather system on this day would be classified as ________

high pressure.

volume and number of moles (n)

increasing the moles of gas at constant pressure means more volume is needed to hold the gas

conditions for a gas to behave like an ideal gas

low pressure high temperature

theories

models that attempt to explain why we observe the behaviors we do. -the gas laws are explained using the kinetic molecular theory

Laws

statements of general behavior based on experimental observations

charle's law

temperature (measured in Kelvin) is proportional to volume. -an increase in temperature at constant pressure results in an increase in volume

average kinetic energy of the molecules is proportional to

the absolute temperature -as the absolute temperature increases, the average velocity increases

A soft drink rises in a straw when you suck on the straw because ________ the vacuum pulls the liquid up the straw. capillary forces attract the liquid to the walls of the straw. the air pressure inside the straw is less than the air pressure outside the straw. the air pressure inside the straw is greater than the air pressure outside the straw. the liquid level inside the straw is pushed up by the liquid level outside the straw.

the air pressure inside the straw is less than the air pressure outside the straw.

u av

the average speed of the molecules

mean free path

the distance a molecule travels between collisions

the total pressure of a mixture depends on

the moles of gas present, not on the identities of gases

u mp

the most probable speed (most molecules are this fast)

partial pressure

the pressure that an individual gas would exert if it were alone in the container

effusion

the process by which a collection of molecules escapes through a small hole into a vacuum

diffusion

the process of a collection of molecules spreading out from high concentration to low concentration

for gases at the same temperature

the rate of gas movement is inversely proportional to the square root of its molar mass

rms average velocity

the rates of diffusion and effusion of a gas are both related to its rms average velocity

u rms

the root-mean-square speed, is the one associated with their average kinetic energy

manometer

used to measure the difference in pressure between atmospheric pressure and that of a gas in a vessel

boyle's law

volume and pressure are inversely proportional. (at constant # moles and temperature) -constant random motion results in collisions with the container, creating pressure -volume and pressure- decreasing the volume of a gas sample means increasing the pressure

avogrado's law

volume occupied proportional to the number of moles of gas. (at constant pressure and temperature) -individual gas particles influence the overall behavior of the gas sample