the gas phase

Question 1

inertia

Answer 1

• Inertia is the resistance of any physical object to any change in its velocity.

Question 2

1atm=

Answer 2

760mmHg

Question 3

760 mmHg or 1 atm =

Answer 3

1 x 10^5 pa

Question 4

standard tempurate and pressure is (STP)

Answer 4

273 K ( 0 degrees C) and 1atm

Question 5

equations for ideal gases assume?

Answer 5

negligible mass and volume of gas particles

Question 6

AT STP 1 MOLE OF ANY IDEAL GAS occupies

Answer 6

22.4 L

( no matter the type of gas, if 2 gases have the same molar amounts (1 mol, 2 mol …) at the same temp and pressure they will occupy the same volume

Question 7

ideal gas law

Answer 7

relationship between P, V, n and T

PV=nRT

Question 8

Avogadro’s principle

Answer 8

special case of ideal gas law!

• P and T constant can relate V and n

n1/V1 = n2/V2

Question 9

Boyles principle

Answer 9

T and n are constant

P1V1=P2V2

Question 10

Charles law

Answer 10

P and n are constant

• V1/T1= V2/T2

Question 11

Gay-Lussacs law

Answer 11

V and n constant

P1/T1= P2/T2

Question 12

combined gas law

Answer 12

combines boyles, charles and gay-lussacs laws-

P1V1/T1= P2V2/T2

Question 13

daltons law

Answer 13

total pressure from partial pressures ( add up all partial pressures )

Question 14

Henery law

Answer 14

the amount of gas dissolved in solution is directly proportional to the partial pressure of that gas at the surface of the solution

[A] = Kh x Pa or [A]i/Pi = [A]f/Pf = Kh

Question 15

we can define the state of a gas asmple by 4 variables

Answer 15

PVTn

Question 16

difference between STP (standard temp and pressure) conditions and standard state conditions

Answer 16

STP = 273 K or 0 C and 1 atm - used for gas law calculations

standard state conditions = 298K (25C), 1atm, 1M - are used when measuring stadard enthalpy, entropy, free energy changes and electrochemical cell voltage

Question 17

what is an ideal gas?

Answer 17

when we do gas questions we assume that the gases are ideal which just means that there are no intermolecular forces and the molecular occupy no volume

Question 18

when do real gases deviate form this

Answer 18

at high P or low T

Question 19

R (ideal gas constant) =

Answer 19

• 8.21 x 10^-2 L-atm/mol K
• or may be 8.3 J/K-mols)
• don’t need to memorize but be aware that it can be expressed in two ways (different units)

Question 20

how to solve ideal gas law questions

Answer 20

• convert al given variables into the appropriate units, solve for x

Question 21

density

Answer 21

p= PM/RT

mass/volume (g/L)
- we can rearange the ideal gas law (bc it contains volume and number of moles)

MM=g/mol –> mol = g/MM

so n= mass/MM

• to know: density (p)= PM/RT

Question 22

what is the density of CO2 at 2 atm and 273 C?

Answer 22

• use combined gas law ( 1 and 2 refer to the states of the gas at STP and at conditions in the question)
• P1V1/T1 = P2V2/T2

V1= at STP 22.4L
P1= 1atm
T1= 273 K 

V2= x
P2= 2 atm 
T2= 273 C + 273 = 546 K 

arrange equation to solve for V2

find MM of Co2

to find density= MM/L/mol = g/L

Question 23

What is the MM of a 22.4L sample of gas that has a mass of 225g at 273 C and pressure of 10atm?

(this one is tricky!)

Answer 23

• identity unknown of gas
• think of the values that have been given as V2, P2 and T2
• we are trying to find the V1 (volume at STP) bc they have given us the mass (in grams) of the unknown compound, so if we have the volume we can find the density (g/L) of gas at STP
• it asks for MM –> g/mol
• multiply density (g/L) by the STP volume of 1 mol (22.4L/mol) to get MM (g/mol)

Question 24

one mol of gas, no matter what type of gas will occupy

Answer 24

22.4 L/ mol at STP

Question 25

gas held at a constant temp

Answer 25

P and V are inversely proportional

- one increase the other decrease

Question 26

if temp increases and pressure is constant

Answer 26

volume increases

Question 27

if n and V are constant, and temp increases

Answer 27

pressure increases

Question 28

when 2 gases are in a container and they don’t chemically interact, how do they behave?

Answer 28

as if they don’t know the other one is in there

• the pressure that each gas exerts (the partial pressure) is the same if the gas is by itself or with another gas
• they act independently

Question 29

the total pressure of the gaseous mixture

Answer 29

the sum of partial pressures

Question 30

the partial pressure of a gas

Answer 30

is related to the mole fraction of each gas and the P total

Pa= Pt x mole fraction

Question 31

mole fraction

Answer 31

moles of x/ total moles

Question 32

Henery noticed that?

Answer 32

at different pressures the concentration of a gas in. a liquid changed

• the solubility of a gas will increase with increasing partial pressure of the gas
• if Pa increase—> [A] increases

Question 33

Vapour pressure

Answer 33

the pressure exerted by evaporated particles above the surface of a liquid

Question 34

solubility/ concentration and pressure

Answer 34

are directly related

Question 35

Grahams law

Answer 35

gases with lower MM will diffuse or effuse faster than those with greater MM

Question 36

Effusion vs Diffusion

Answer 36

• effusion - movement from one container to another through small opening
• diffusion- spreading out of particles in the same container

Question 37

when do gases deviate from ideal gases

Answer 37

when variables (P,T,V) are changed in a way that brings them very close together

• High P
• Low V
• Low T –> bc there movement slows and their intermolecular forces become moe significant!

Question 38

root-mean square speed

Answer 38

Urms= Square root of (3RT/MM)

• M in kg/mol