The Gas Phase

Question 1

STP condictions

Answer 1

T= 273 K (0 degree C)
P= 1atm
-used with gases

Question 2

Standard conditions

Answer 2

T= 298K (25 degree C)
P= 1atm
Concentration= 1M

Question 3

Characteristics of gases

Answer 3

Gases are compressible fluids with rapid motion, large intermolecular distances, and weak intermolecular forces

Question 4

Mercury Barometer

Answer 4

• When the external air exerts a higher force than the weight of the mercury in the column, the column rises.
• When the external air exerts a lower force than the weight of the mercury, the column falls

Question 5

Ideal Gases

Answer 5

Represents a hypothetical gas with molecules that have no intermolecular forces and occupy no volume

Question 6

Ideal Gas Law

Answer 6

PV=nRT

R= .0821

Question 7

Density

Answer 7

Ratio of the mass per unit volume of a substance

Shortcut to finding density- ρ = m/V = PM/RT

Question 8

Avogadro’s Principle

Answer 8

• Which states that all gases at a constant temperature and pressure occupy volumes that are directly proportional to the number of moles of gas present
• n1/V1 = n2/V2
• As the number of moles of gas increases, the volume increases in direct proportion

Question 9

Boyle’s Law

Answer 9

P1V1 = P2V2

As pressure increases, volume decreases (inverse log)

Question 10

Charles Law

Answer 10

V1/T1 = V2/T2

As temperature increases, volume increases (linearly)

Question 11

Gay-Lussac’s Law

Answer 11

P1/T1 = P2/T2

As temperature increases, pressure increases (linearly)

Question 12

Dalton’s Law of Partial Pressure

Answer 12

Pa = XaPt
Pa is the partial pressure of the gas a
Xa is the mole fraction of a, which is the moles of gas a/ total moles of gas

Question 13

Henry’s Law

Answer 13

[A] = kH x Pa or [A1]/P1 = [A2]/P2 = kH

• [A] is the concentration of A in solution, kH is Henry’s constant, and Pa is the partial pressure of the gas
• Solubility of a gas will increase with increasing partial pressure of the gas

Question 14

Kinetic Molecular Theory Assumptions

Answer 14

• Gas made of particles whose volumes are negligible compared to container volume
• Gas molecules exhibit no intermolecular forces
• Gas is in continuous, random motion, undergoing collisions with other particles and the wall
• Collisions are elastic, meaning that there is conservation of both momentum and kinetic energy
• Average kinetic energy of gas particles is proportional to the absolute temperature of the gas, and it is the same for all gases at a given temperature, irrespective of chemical identity or atomic mass

Question 15

Kinetic Molecular Theory of Gases

Answer 15

-Average kinetic energy of a gas particle is proportional to the absolute temperature of the gas
KE = 3/2kbT where kb is the Boltzann’s constant (1.38x10^23 J/K)

Question 16

Root Mean Square Speed (urms)

Answer 16

urms = sqrt(3RT/M)

Question 17

Maxwell-Boltzmann Distribution Curves

Answer 17

The more massive the gas particles, the slower their average speed

Question 18

Graham’s Law

Answer 18

r1/r2 = sqrt(M2/M1)

Question 19

Deviation Due to Pressure

Answer 19

• AS the condensation pressure for a given temperature is approached, intermolecular attraction forces become more and more significant
• As the temperature of a gas is decreased, the average speed of the gas molecules decreases and the attractive intermolecular forces become increasingly significant

Question 20

Van der Waals Equation of State

Answer 20

(P + n^2a/V^2)(V-nb) = RT
-a corrects for the attractive forces between molecules. The more polarizable the molecule, the larger the a value
b corrects for the volume of the molecules themselves. Larger molecules thus have larger values of b.