8: The Gas Phase

Question 1

units of gas pressures

Answer 1

1 atm = 760 mmHg = 760 torr = 101.325 kPa

Question 2

STP conditions

Answer 2

273 K, 1 atm, *not same as standard state conditions (298 K, 1 atm, 1 M)

Question 3

ideal gas

Answer 3

represents a hypothetical gas with molecules that have no intermolecular forces and occupy no volume… real gases deviate at high pressures (low volumes) and low temperatures

Question 4

ideal gas law

Answer 4

PV=nRT

• R = 0.0821 L•atm/mol•K OR 8.314 J/K•mol
• use ideal gas law to find molar mass or denisty

Question 5

denisty

Answer 5

density = mass/volume

density =m/V = PM/RT

Question 6

combined gas law

Answer 6

Question 7

Avogadro’s Principle

Answer 7

as the number of noles of gas increases, the volume increases in direct proportion

n₁/V₁ = n₂/V₂

Question 8

Boyle’s law

Answer 8

derivation of the ideal gas law that states that pressure and volume are inversely related

P₁V₁ = P₂V₂

Question 9

charles’s law

Answer 9

derivation of the ideal gas law that states that volume and temperature are directly proportional

V₁/T₁ = V2/T₂

Question 10

Gay-Lussac’s law

Answer 10

temperaure and pressure are directly proportional

P₁/T₁ = P₂/T₂

Question 11

Dalton’s law of partial pressures

Answer 11

when one or more gas is in a container, each contributes to the whole as if it were the only gas present

P_T = P_A + P_B + P_c + …

P_A = X_AP_T

X_A = moles of gas A/total moles of gas

Question 12

Henry’s law

Answer 12

solubility of gas will increase with increasing partial pressure of gas

[A] = K_H x PA

[A]₁/P₁ = [A]2/P₂

[A] is concentration of A in solution

Question 13

kientic molecular theory

Answer 13

accounts for observed behavior of gases; cosiders gas molecules to be pointlike, columeess particles exhibiting no intermolecular forces that are in constant random motion and undergo only completely elastic collisions with the container or other gas particles

Question 14

average inetic energy of a gas particle

Answer 14

KE= 1/2 mv²= 3/2 K_BT

• the higher the temperature, the faster the molecules move. the larger the molecules, the slower they move

Question 15

root-mean-square speed

Answer 15

one way to define average speed

R = 8.313 J/mol•K

J=kg/mo;

Question 16

Maxwell-Botlzmann distribution curve

Answer 16

shows distribution of gas particle speeds at a given temperature

Question 18

Graham’s law of diffusion and effusion

Answer 18

under isothermal and isobaric conditions, the rates at which 2 gases diffuse are inversely proportional their molar masses… both diffusion and effusion are slower for larger molecules

Question 19

real gases

Answer 19

real gases deviate from ideal gas behavior when gas atoms/molecules are forced into close proximity under high pressure (low volume) or low temperature

• real gas particles take up space and have intermolecular forces

Question 20

van der waals equation of state

Answer 20

a and b are physical constants experimentally determined for each gas…

• a corrects for the attractive forces between molecules
  
  • smaller for gases that are small and less polarizable, largest for polar molecules
• b corrects for the volume of the molecules themselves