Chapter 5: Gas Laws & Kinetic Molecular Theory

Question 1

Gas volume changes significantly with pressure but…

Answer 1

solids and liquids are not greatly affected by pressure

Question 2

Gas volume changes significantly with temperature

Answer 2

gases expand when heated and shrink when cooled; volume change is 50-100 times greater than for liquids or solids

Question 3

Gases flow very freely and have relatively low densities; gas particles are very far apart and fill available space of their container

Answer 3

Other physical states/properties of gases

Question 4

Gases form a solution in any proportions

Answer 4

they are freely miscible with each other

Question 5

Atmospheric pressure arises from the force exerted by atmospheric gases on the earth’s surface

Answer 5

Atmospheric pressure decreases with altitude.

Question 6

When the pressure of the gas is less than the pressure of the atmosphere, subtract the difference from the total atmospheric pressure

Answer 6

If P(gas) < P(atm):
[P(gas) = P(atm) - delta h]

Question 7

When the pressure of the gas is greater than the pressure of the atmosphere, add the difference to the pressure of the atmosphere

Answer 7

If P(gas) > P(atm):
[P(gas) = P(atm) + delta h]

Question 8

“Ideal gas molecules do not attract or repel each other”–if the interparticle attraction between gas molecules is great enough, the gas will deposit into a liquid or condense into a solid (i.e. dry ice and liquid helium)
AND
“the volume of an ideal gas molecule is negligible compared to the volume of the container”–if this were the case then it would be possible to compress a gas enough so that it does not occupy any volume, which is impossible.

Answer 8

Gases do not always behave ideally in the real world

Question 9

w = -PdeltaV or w = -nRT

Answer 9

A system that does work on the surroundings has a negative value for ‘work’
A system that has work done on it by the surroundings has a positive value for work

Question 10

delta V and delta n are positive integers if there is an increase in the # of moles of gas as the reaction proceeds; (P, T, and R always have positive values)

Answer 10

• If a reaction produces more moles of gas than it consumes then:
• deltaV and delta n are positive and Work is negative
• it did work on the surroundings

Question 11

delta V and delta n are negative if there is a decrease in the # of moles of gas as the reaction proceeds; (P, T and R always have positive values)

Answer 11

• If a reaction consumes more moles of gas than it produces then:
• deltaV and delta n are negative and Work is positive
• it had work done to it by the surroundings

Question 12

mass =

Answer 12

volume x density

Question 13

delta T =

Answer 13

T (final) - T (initial)

Question 14

used to measure the pressure of a gas

Answer 14

manometer

Question 15

PV = nRT

T = temperature---*always in Kelvin
P = pressure--usually in atm or mmHg, also torr 
n = amount (in moles usually)
R = gas constant 0.0821 L*atm/mol*K
V = volume

Answer 15

Ideal Gas Law

• can be rearranged in several different ways to find certain values
• ideal gases exhibit linear relationships
• no ideal gas actually exists but most behave nearly this way at ordinary temperature and pressure

Question 16

mass/volume =

Answer 16

density

Question 17

mass (g) / molar mass (m/g) =

Answer 17

moles (n)

Question 18

Molar Mass -

Answer 18

mRT/PV

Question 19

E  = (1/2)m x v^2 = (1/2mass x speed^2)
F = ma (force = mass * area)

Answer 19

*At a given T, all gases in a sample have the same average kinetic energy
*Kinetic energy depends on both the mass and speed of the particle
*At a higher mass, gas moves slower (at constant T) and has a lower rate of effusion
(and vice versa)

Question 20

273.15K, 0*C, 1 atm & 760 mm Hg/torr

Answer 20

STP, Standard Temperature & Pressure

Question 21

22.41L–the volume of an ideal gas at STP

Answer 21

Standard Molar Volume

Question 22

[ deltaE(system) + deltE(surroundings) ]

Answer 22

E(universe) =____________________= 0

Question 23

P1 * V1 / T1 =

Answer 23

P2 * V2 / T2

Question 24

PV = (mass/molar mass)RT

Answer 24

m/V = d = (molar mass x P) / RT

Question 25

0.0821 Latm/molK

Answer 25

gas constant R

Question 26

n = mass/molar mass = PV/RT

Answer 26

molar mass = mRT/PV

Question 27

gases mix homogeneously in any proportions

-each behaves in a mixture as if it was the only one

Answer 27

pressure of each gas exerted in a mixture =

partial pressure

Question 28

the total pressure in a mixture is the sum of the partial pressures of all the gases in the mixture

Answer 28

Dalton’s Law of Partial Pressures

Question 29

partial pressure, X(A) =

n(A )/ n(total)

Answer 29

the partial pressure of a gas is proportional to its mole fraction

Question 30

the process by which a gas escapes through a small hole in its container into an evacuated space

Answer 30

effusion

Question 31

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

Answer 31

Graham’s Law of Effusion

rate of eff ~ 1 / root^2(molar mass)

Question 32

Real gases have real volume

Real gases do experience attractive and repulsive forces between their particles

Answer 32

Real Gases: deviation from ideal behavior

*real gases deviate most at low temperature and high pressure

Question 33

-50*C / 223-500K / 1-3/5 atm

Answer 33

Gases tend to behave normally over these ranges