Chapter 8

Question 1

Force

Answer 1

= mass x acceleration

Question 2

Pressure

Answer 2

The total amount of force exerted
by gas molecules hitting the entire
surface at any one instant, is the
pressure the gas is exerting

Pressure = force/area

Question 3

Newton (N)

Answer 3

Force of air:
F = ma = (10,000 kg)(9.8 m/s2)
F = 1x105 kg·m/s2
F = 1x105 N
✓SI unit of force is Newton (N)
✓1 N = 1 kg·m/s2

Question 4

Pascal (Pa)

Answer 4

Atmospheric pressure:
P = F/A = (1x105 N)/(1 m2) = 1x105 N/m2
P = 1x105 Pa
✓SI unit of pressure is Pascal (Pa)
✓1 Pa = 1 N/m2 = 1 kg/m·s2

Question 5

Pressure

Answer 5

As pressure increases, surface area decreases

Question 6

Manometers

Answer 6

• The pressure of a gas in a container can be measured with a manometer
• Two types of manometers:
  ✓ open-ended or closed-ended
• Difference in liquid levels is a measure of the difference in pressure between the gas and the other end of tube
  ✓ Open-ended manometer:
  Pgas = Patm + hg
  ✓ Closed-ended manometer:
  Pgas = hg

Question 7

Amonton’s Law

Answer 7

Pressure of a gas is
directly proportional to its
temperature

Pressure/tempeture=constant

✓constant V and amnt of gas
✓if T measured in Kelvin

Question 8

Amonton’s Law

Answer 8

The pressure of a gas is directly proportional to its
temperature.

P/T=constant

Question 9

Charles’ Law

Answer 9

Volume of a gas is directly proportional to temperature

✓constant P and amnt of gas
✓if T measured in Kelvin

V/T=constant

Question 10

Boyle’s Law

Answer 10

The pressure of a gas is inversely proportional to its volume.

As the volume goes up, the pressure goes down.

✓constant Tand amount of gas

PV=constant

Question 11

Avogadro’s Law

Answer 11

Volume directly proportional to the number of gas molecules

✓constant P and T

V/n=constant

Question 12

Ideal Gas Law

Answer 12

Ideal gas: a hypothetical case described by
the idea gas law

PV=nRT

• T is temperature in K
• n is number of moles
• V is volume
  ✓different units used: mL, L, m3
• P is pressure
  ✓different units used: atm, Pa, bar, torr
• Pressure x volume = energy
  ✓SI unit of energy is the Joule (J)
  (Pa)(m3) = (N/m2)(m3) = (kg·m/s2)/m2
  = kg·m2/s2 = J
• R is the ideal gas constant
  ✓ can be given in a variety of units

Question 13

Standard Temperature

Standard Pressure

Answer 13

Temperature: 273.15

Pressure: 1 atm

Question 14

Molar volume of a gas

Answer 14

22.4L

Question 15

Mole Fraction

Answer 15

The fraction of the total pressure that a single gas contributes = the fraction of the total moles that a single gas contributes

Question 16

Diffusion

Answer 16

• The rate of molecules spreading out from high concentration to low concentration is diffusion
• Gases will spread from a region of high concentration to a region of low concentration,
  ✓Until the concentration is the same throughout
• Rate of diffusion: the amount of gas passing through

Question 17

Mean Free Path

Answer 17

Molecules in a gas travel in
straight lines until they collide
with another molecule or the
container

The average distance a molecule
travels between collisions is the
mean free path

Question 18

Effusion

Answer 18

The escape of gas particles through a small hole
into a vacuum (or low pressure) is effusion
* Like diffusion, rate of effusion is inversely
proportional to the square root of the molar mass:

Question 19

Graham’s Law of Effusion