Chemistry Video 10

Question 1

Kinetic molecular theory

Answer 1

Describes ideal gases.

1. A gas is made of particles that are in motion.
2. Gases are mostly empty space. The volume of gas particles is negligible.
3. Pressure is force of particles on the container. More collisions = more pressure
4. Gas particles do not interact. Collisions are elastic and occur without loss of kinetic energy
5. Average kinetic energy of the particles in the gas is proportional to the temperature of the gas in Kelvins. If you increase temperature, then the kinetic energy is increased and the particles move faster.

Question 2

Boyle’s Law

Answer 2

Pressure and volume are inversely proportional.

P1V1 = P2V2

Question 3

Charles’s Law

Answer 3

Volume and temperature are directly proportional.

V1/T1 = V2/T2

Question 4

Combined gas law

Answer 4

(P1V1)/T1 = (P2V2)/T2

Question 5

Avogadro’s Law

Answer 5

Equal volumes of different gases have the same number of moles (if under the same temperature and pressure)

V1/n1 = V2/n2

Volume and moles are proportional (at constant temperature and pressure)

Question 6

Standard temperature and pressure

Answer 6

1 mole of any ideal gas at T = 0 degrees Celsius and P = 1 atm will occupy Volume of 22.4 L.

STP conditions are T = 0 degrees Celsius and P = 1 atm

Question 7

Density

Answer 7

Grams / Liter

Question 8

Ideal gas law

Answer 8

PV = nRT
It applies to ideal gases. Works well for gases at low pressure and high temperature.

R = ideal gas constant
R = 0.08206 L atm/mol K
R = 8.314 kPa L/mol K

1 atm = 760 torr = 760 mmHg

Question 9

Dalton’s Law

Answer 9

Total pressure = sum of the partial pressures

Question 10

Mole fraction

Answer 10

Moles of a substance compared to the total moles of matter present

Question 11

Partial pressure

Answer 11

mole fraction * total pressure

Question 12

Mean Free Path

Answer 12

Average distance a molecule of gas travels between collisions. Typically around a few hundred times its diameter. This changes according to pressure of gas and moles

Question 13

Diffusion

Answer 13

Particles move from area of high concentration to area of lower concentration, until the concentrations become equal

Question 14

Diffusion Rate

Answer 14

Depends on…

1. Concentration gradient
2. Surface area available for diffusion. Small surface area = slow diffusion. Large surface area = fast diffusion
3. Distance to diffuse. Farther distance to travel means a slower rate of diffusion

Question 15

Effusion

Answer 15

Process by which gas particles escape through a tiny hole in their container. Small surface area for particles to move. Rate depends on molar mass of gas. Heavier gas = slower movement

Question 16

Graham’s Law of Effusion

Answer 16

Rate of effusion is inversely proportional to the square root of the molar mass of a gas

Rate A / Rate B = [sqrt (molar mass B)] / [sqrt (molar mass A)]

Question 17

Non-ideal gases

Answer 17

Real gases. Gases deviate from ideal gas behaviour at high pressures and low temperatures.

Question 18

Van der Waals Equation

Answer 18

Describes non-ideal gas behaviour. Used when conditions are not ideal gas conditions.

(P + an^2/V^2)*(V - nb) = nRT

Adjust the pressure term with a correction factor associated with the attraction between the gas particles.

a = constant describing the strength of the attractions between gas particles. Larger and more polar particles have stronger attractions than non-polar particles.

Adjust the volume term with a correction factor associated with the volume occupied by the gas particles.

b = constant describing the size of the gas particles.

Each gas has its own a and b values

This equation is reduced to ideal gas law of PV = nRT under ideal gas conditions, where V is big and n is small.

Question 19

Gay-Lussac’s Law

Answer 19

Pressure and temperature are directly proportional at constant volume