Ch. 8: The Gas Phase

Question 1

Properties of Gases

Answer 1

Least dense phase of matter, fluid–conform to the shapes of their containers, easily compressible

Question 2

Gas System Variables

Answer 2

Temp, Pressure, Volume, Number of Moles (n)

Question 3

Important Pressure Equivalencies

Answer 3

1 atm = 760 mmHg = 760 torr = 101.325 kPa

Question 4

Simple Mercury Barometer

Answer 4

Measures incident (usually atmospheric) pressure. Increase in pressure = more mercury in column= increase in height. Decrease in pressure = mercury flows out of column = decrease in height

Question 5

Standard Temperature and Pressure (STP)

Answer 5

273 K (0*C) and 1 atm

Question 6

Assumptions for ideal gas equations

Answer 6

Negligible mass and volume of gas molecules, regardless of the identity of the gas, equimolar amounts of 2 gases will occupy the same volume at the same temp and pressure. At STP, one mole of an ideal gas occupies 22.4 L

Question 7

Ideal Gas Law

Answer 7

Describes the relationship between the 4 variables of the gas state for an ideal gas

Question 8

Avogadro’s Principle

Answer 8

Special case of the ideal gas law for which the pressure and temp are held constant; it shows a direct relationship between the # of moles of gas and volume

Question 9

Boyle’s Law

Answer 9

Special case of the ideal gas law for which temp and number of moles are held constant; it shows an inverse relationship between pressure and volume

Question 10

Charles’s Law

Answer 10

Special case of the ideal gas law for which pressure and number of moles are held constant; it shows a direct relationship between temp and volume

Question 11

Gay-Lussac’s Law

Answer 11

Special case of the ideal gas law for which volume and number of moles are held constant; it shows a direct relationship between temp and pressure

Question 12

Combined Gas Law

Answer 12

Combo of Boyle’s, Charles’s, and Gay-Lussac’s laws; shows an inverse relationship between pressure and volume along w direct relationships between pressure and volume w temp

Question 13

Dalton’s Law of Partial Pressures

Answer 13

States that individual gas components of a mix of gases will exert individual pressures in proportion to their mole fractions. The total pressure of a mix of gasses is equal to the sum of the partial pressures of the component gases

Question 14

Henry’s Law

Answer 14

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

Question 15

Kinetic Molecular Theory

Answer 15

• gas particles have a negligible volume
• gas particles do not have intermolecular attractions or repulsions
• gas particles undergo random collisions w each other and the walls of the container
• collisions between gas particles (and with the walls of the container) are elastic
• avg kinetic energy of the gas particles is directly proportional to the temp

Question 16

Graham’s Law

Answer 16

Describes the behavior of gas diffusion or effusion, stating that gases w lower molar masses will diffuse or effuse faster than gases w higher molar masses at the same temp

Question 17

Diffusion

Answer 17

Spreading out of particles from high to low concentration

Question 18

Effusion

Answer 18

Movement of gas from one compartment to another through a small opening under pressure

Question 19

Real Gases

Answer 19

Deviate from ideal behavior under high pressure (low volume) and low temp conditions

Question 20

Deviations:

Moderately High Pressure, low volumes, or low temps

Answer 20

Real gases will occupy less volume than predicted by the ideal gas law bc particles will have intermolecular attractions

Question 21

Extremely high pressures, low volumes, or low temps

Answer 21

Real gases will occupy more volume than predicted by the ideal gas law bc the particles occupy physical space

Question 22

van der Waals eqn of state

Answer 22

Used to correct the ideal gas law for intermolecular attractions (a) and molecular volume (b)