Chapter 8: The Gas Phase

Question 1

Pressure units

Answer 1

1 atm = 760 mmHg = 760 torr = 101.325Kpa

Question 2

Ideal Gas Law

Answer 2

PV = n R T

P = pressure
V = volume
n = moles
R = ideal gas constant (8.21 x 10^-2 L. atm / mol . K)

Question 3

Convert K to C or vice versa

Answer 3

T = (temp in C) + 273 = (temp in K)

Question 4

Density

Answer 4

ρ = m / V

m = mass
V = volume

Question 5

Ideal gas AND density

Answer 5

m/v = PM / RT

M = molar mass

Question 6

Combined Gas Law

Answer 6

P1 V1 / T1 = P2 V2 / T2

Question 7

Combined Gas Law Rearranged

Answer 7

V2 = V1 [P1/P2][T2/T1]

Question 8

Molar Mass

Answer 8

M = (ρstp) (22.4 L /mol)

product of gas’s density at STP times the STP volume of one molar of gas 22.4 L/mol

Question 9

Avogadro’s Principle

Answer 9

n/V = k

n1/ V1=n2/ V2

Question 10

Boyle’s Law

Answer 10

PV = k

P1V1 = P2V2

n and T are constant, pressure and volume are inversely related

Question 11

Charles’s law

Answer 11

V/T= k

V1/T1= V2/T2

n and P are constant, temperature and volume are directly proportional

Question 12

Gay-Lussac’s law

Answer 12

P/T = k

P1/T1= P2/T2

n and V are constant, temparature and pressure are directly proportional

Question 13

Dalton’s law of partial pressure

Answer 13

Pt= Pa + Pb + Pc + …..

Pt = total pressure
Pa = partial pressure of gas A

Question 14

Partial Pressure

Answer 14

Pa = Xa Pt

Pt = total pressure
Pa = partial pressure of gas A
Xa = mole fraction

Question 15

Mole Fraction

Answer 15

Xa = moles of gas A / total moles of gas

Question 16

Henry’s law

Answer 16

[A] = kh x Pa

[A]1 /P1 = [A]2 / P2

[A] = concentration of A in solution
kh = henry’s constant
Pa = partial pressure pf A

Question 17

Average Molecular Speeds

Answer 17

KE = 1/2 mv^2 = 3/2 kb T

kb = boltzman constant (1.38 x 10^23 J/K)

Question 18

Root-mean- square speed (urms)

Answer 18

urms = √’3RT/M

R = ideal gas constant
T = temperature
M = molar mass

Question 19

Graham’s law

Answer 19

r1/r2 = √’M2/M1

r1 and r2 are the diffusion rates of gas 1 and 2
M1 and M2 are the molar masses of gas 1 and 2

Question 20

van der Waals Equation of state

Answer 20

(P + n^2 a / V^2) (V - n b ) = n R T

P = pressure
R = universal gas constant
T = absolute temperature
V = molar volume
b = gas constant b, term for big particles
{a} = gas constant a, term for the attractive forces
V = molar volume
n = moles