Gas Laws

Question 1

Kinetic Molecular Theory of Gases

Answer 1

• UNDER IDEAL CONDITIONS!!*
  1. Volume of a gas particle is negligible compared to the spaces between the molecules.
  2. Gas particles are in constant, random translational motion.
  3. The pressure exerted by a gas is the results of collision of the gas particles. When particles collide with each other and the walls of the container, there is NO loss of kinetic energy. The collision is elastic.
  4. There is neither attraction nor repulsive forces between gas particles.
  5. The average kinetic energy of a gas is directly related to the Kelvin temperature of the gas.

Question 2

Ideal Conditions

Answer 2

Low pressure & high temperature

Question 3

Pressure

Answer 3

The force on a given area

P = F/A

Question 4

Barometer

Answer 4

Measures atmospheric pressure (height of mercury)

Question 5

Boyle’s Law

Answer 5

The pressure and volume of a fixed mass of a gas are inversely related at constant temperature. (PV = k) k is a constant
P ∝ 1/V @ constant T
^As pressure changes, so does the volume but in opposite directions
*GRAPH: P(x) & V(y) — negative & curved

Question 6

Charles Law

Answer 6

The temperature and volume of a fixed mass of a gas are directly related at constant pressure (V/T = b) b is a constant
V ∝ T @ constant pressure
^As temperature changes, so does the volume in the same direction
*GRAPH: T(x) & V(y) — positive and linear *note: dashed line for first part of trend line because there is no gas at absolute zero, 0 K

Question 7

Gay-Lussac’s Law

Answer 7

The pressure and temperature of a fixed mass of a gas are directly related at constant volume (P/T = c) c is a constant
P ∝ T @ constant V
^As temperature changes, so does the pressure in the same direction
*GRAPH: T(x) & P(y) — positive linear trend line

Question 8

Avagadro’s Law

Answer 8

At a constant temperature and pressure, the volume and number of moles of a gas are directly related (V/n = a) a is a constant
V ∝ n @ constant temperature and pressure

Question 9

Ideal Gas Law

Answer 9

Combining the other gas laws generates a new equation that shows how the volume, pressure, temperature and number of moles of gas are related.
PV = nRT
IDEAL CONDITIONS

Question 10

Standard Temperature & Pressure (STP)

Answer 10

Standard temperature: 0°C (273 K)
Standard pressure: 1 atm (101.325 kPa)
*@ STP, 1 mole of an ideal gas occupies a volume of 22.4 L (molar volume of ideal gas)

Question 11

Standard Ambient Temperature and Pressure (SATP)

Answer 11

Temperature: 25°C
Pressure: 100kPa

Question 12

Combined Gas Law

Answer 12

If all 3 variables are allowed to change (PV/T = constant)

(P initial x V initial) / T initial = (P final x V final) / T final

Question 13

Dalton’s Law of Partial Pressure

Answer 13

For a mixture of gases in a container, the total pressure exerted is the sum of the pressures of the individual gases (P total = P1 + P2 + P3 + …)

Question 14

Water Vapour Pressure

Answer 14

P total = P(O2) + P(WV)

Question 15

Mole Fraction

Answer 15

The ratio of the number of moles of a gas in a mixture to the total number of moles in the mixture is called mole fraction (n total = n1 + n2 + n3 + …)
x1 = n1/n total x2 = n2/n total x3 = n3/n total
x1 = P1/P total x2 = P2/P total x3 = P3/P total

Question 16

Graham’s Law of Diffusion & Effusion

Answer 16

The rate of diffusion or effusion of a gas is inversely related to the square root of the molar mass or the gas
r1/r2 = (M2/M1)^1/2
r ∝ 1/(square rood of M)
*Units: L/s, L/min, mL/s, mL/min
*Note: Heavier moves slower

Question 17

Diffusion

Answer 17

Term used to describe mixing of gases

Question 18

Effusion

Answer 18

Term used to describe the passage of a gas through a tiny orifice into a vacuum chamber

Question 19

Real Gases

Answer 19

A real gas consists of particles that take up space themselves, the volume available to a given particle is less than the volume of the container. Therefore, the actual volume of the gas equals the volume of the container minus a correction factor for the volume of the molecules
P = nRT/(V - nb)
*nb: correction factor
*n: # of moles
*b: empirical constant (table)

Question 20

Gas Lab

Answer 20

Pressure exerted by water column equation:

h(Hg) = h(H2O)/13.58