Week 1 - Chem

Properties of Gases

indefinite shape and volume

exert pressure

volume assumes its container

low density

SI unit for pressure

pascal (Pa)

1 newton / m2

1 atm = 101, 325 Pa or 101.3 kPa

Standard Temp and Pressure

temp = 273.15 K (0 degrees celcius)

pressure = 1 atm or 760 torr, or 760 mmHg or 101.325 kPa

at STP, 1 mole = 22.4L of volume

Boyle’s Law

Pressure and Volume

P1 V1 = P2 V2

Charles Law

Volume and Temp Relationship

V1 / T1 = V2 / T2

Gay - Lussacs Law

Pressure and Temp

P1 / T1 = P2 / T2

Combined Gas Law

Pressure, Volume and Temp Relationship

P1 V1 / T1 = P2 V2 / T2

Avogrado’s Law-Quantity (mole) and Volume Relationship

V1 / N1 = V2 / N2

Dalton’s Law - Partial Pressure

total pressure of a mixture of gases is just sum of pressure that each gas would exert if it were present alone

Ideal Gases

have own molar mass

have kinetic energy

collide with each other and interactions perfectly elastic

• exert pressure due to collision of gas molecules with wall of container

• no attractive forces

• no repulsive forces

Ideal Gas Law

1. the volume

2. the pressure

3. the absolute temp

4. the number of molecules/ moles

PV = nRT

Kinetic Molecular Theory

Principal Assumptions

• Gas = tiny particles

• Distance between particles large; volume occupied mostly empty space

• Gas particles no attraction for one another

• Gas particles move in straight lines

• No energy lost in collision (All perfectly elastic)

• Average kinetic energy the same at same temp

Effusion of Gas

movement of gas into a vacuum

rate inversely proportional to molar mass (lighter gas = faster effusion through holes)

Diffusion of Gas

mixing of 2 or more gases

average rate of movement dependent on temp and molar mass (faster for smaller)

Intermolecular Forces

1. exist between molecules but also between atoms and ions

2. generally weaker than bonding forces within compounds

3. influence physical properties

4. rely on attraction between positive and negative regions

Intramolecular Forces

infleunce molecular shape and bond energies

(Van Der Walls)