Unit 3: IMF, Gas Laws

Boyle’s Law

P₁V₁ = P₂V₂

Charles’ Law

V₁     V₂

T₁ = T₂

• pressure and moles are constant

Gay-Lussac’s Law

P₁      P₂

T₁  =  T₂

• volume and moles are constant

Avogadro’s Law

V₁    V₂

n₁ =  n₂

• pressure and temperature are constant

Ideal Gas Law

PV = nRT

Combined Gas Law

• when number of moles of gas is constant

Dalton’s Law of Partial Pressures

P_total = P_A + P_B + P_C …

Open system

system that allows the open transfer of energy and matter/mass

Closed system

system that allows the transfer of energy only

Isolated system

system that does not allow the transfer of either energy or matter

System

the volume that contains matter chemical and physical properties

Intensive property

Amount independent; properties with values that do not add

• EX: temperature and pressure

  • two water samples at 100 degree C do not total 200 when poured together

Extensive property

Amount dependent; properties that do add together

• EX: volume and moles

State functions

depends only on how it ends (change of final - initial)

• EX: temperature, volume, pressure, moles of gas, enthalpy, entropy, internal energy, Gibbs free energy

Path function

function that keeps track of what is happening between the beginning and end

• EX: heat, q, and work, w

KMT assumptions

1. gas particles have no volume

2. gas particles undergo elastic collision (KE is conserved)

3. gas particles have a KE that is proportional to temperature

4. gas particles have a velocity that varies as the inverse square of the mass

Which KMT assumptions are flawed?

1. Gas particles DO have volume

2. Gas particles can undergo collision that are inelastic (EX: water that sticks at room temp)

At room temp, which of the naturally diatomic atoms is solid at room temp?

I₂

At room temp, which of the naturally diatomic atoms is liquid at room temp?

Br₂

Molecular Weight

Density (also include substitution into IGL)

p = m/v

What is the volume of 1 mole of gas at STP?

22.4 L

Consider the Maxwell-Boltzmann distribution of gases, if m stays constant, then as T increases…

V increases; KE increases

Consider the Maxwell-Boltzmann distribution of gases, if T stays constant, then as m increases…

V decreases

Graham’s Law of Diffusion/Effusion

What are the ideal conditions for an ideal gas?

Collisions are rare and elastic

How can you manipulate each variable of IGL to make conditions of a gas more ideal?

• P is low so don't collide

• V is large so don't collide

• n is small so don't collide

• T is large so don't stick

Consider the van der Waals correction factors, what does “a” correct?

“a” corrects for stickiness aka IMF

• Large gases (molecular weight) and polar gases have large a, while small nonpolar gases have small a.

Consider the van der Waals correction factors, what does “b” correct?

“b” corrects for size

• Large molecules (molecular weight) have large b, small molecules have small b.

Dispersion forces increase as

Molecular weight increases

Dipole-dipole forces increase as

The change in electronegativity increases

Hydrogen bonding increases as

the number of hydrogen bonds increase OR N-H < O-H

Ionic IMF increases as 

Charge density increases (charge number and size)

Define boiling point and relationship to IMF

Bulk phenomenon in which the atmospheric pressure equals the vapor pressure of the liquid, causing the liquid to become a vapor.

• Direct to IMF.

Define surface tension and relationship to IMF

Surface phenomenon in which an inward force reduces the surface area of liquid. This is why liquids like H2O bead up on windrows in the rain.

• Direct to IMF.

Define capillary action and relationship to IMF

Surface phenomenon in which the liquid climbs the walls of the container because of IMF.

• Direct to IMF.

Define viscosity and relationship to IMF

Tendency of a liquid to resist pouring because of IMF attraction to bulk solution.

• Direct to IMF.

Define Heat of Vaporization and relationship to IMF

The energy in IMF that must be overcome for a liquid on the surface to vaporize (become gas)

• direct to IMF

Define vapor pressure and relationship to IMF

Pressure of the vapor above the surface of a liquid

• inverse to IMF

Define evaporation rate and relationship to IMF

How quickly a liquid will vaporize from the surface of a liquid

• inverse to IMF

Order the h-bonds

NH₃ < HF < H₂O

• NH₃ - small EN even though it has 3 h bonds

• HF - larger EN but only one h bond

• H₂O - sizeable EN and 2 h bonds