CHEM EXAM 4

Atmospheric Science

the study of gases in the atmosphere and the reactions they undergo

Gas Characteristics

No definite shape or vol
Compressible
Low density changing based on temp and V

Units of gas density

g/L

If temperature increases density

density decreases

If volume increases then density

density decreases with the volume

Gases exert

Pressure

Atmospheric pressure

Pressure exerted by the gases in the air on everything inside the earth’s atmosphere

Barometer

device used to measure pressure

Units of pressure

atm
mmHg
torr

Units of pressure conversions

760mmHg=1atm=760torr

4 parameters of gas

Pressure
Volume
Moles
Temp

Directly proportional

As one increases the other increases
(y-x) opposite sides of equation x=y

Inversely proportional

As one increases the other decreases
(y-1/x) same side xy=0

Boyle’s Law relates

Pressure and Volume, constant T and N

Boyle’s law experiment

J-Tube experiment

J-Tube Experiment relationship

inversely, as P increases, V decreases and vice versa

Charle’s Law relates

Volume and Temperature, constant P and N

Charle’s Law Relationship

Direct, as Volume increases T increases

Avogadro’s Law relates

moles of gas to volume, constant T and P

Avogadro’s Law relationship

Directly, as n increases V increases

Ideal Gas equation(only used by GASES)

PV=nRT

Mole fraction (X)

ratio of the moles of a given gas to the total # of moles in a mixture of gases

Kinetic Molecular Theory

Attempts to explain why gases follow the ideal gas law

KMT #1.

G particles are so small that the V of each particle is negligible.

KMT #2.

g particles are in constant motion colliding with walls = pressure

KMT #3.

g particles assert no force on each other

KMT #4.

g particle collision are elastic, no kinetic energy lost

KMT #5.

Avg kinetic energy of a g particle is proportional to T only

Gas particles move by

Diffusion

Two generalizations of gas particles

As size increases, speed decreases
As T increases, speed increases

Random walk Principle

gas particles travel in a straight line until they collide with something, changing the direction

Mean free path

shortest distance between starting and ending points

Liquid characteristics

Definite volume, no shape
Polar liquids used as solvents (H2O)

Solids characteristics

Fixed shape
Fixed Volume
Incompressible

Hydrogen bonding importance

Supports life on earth

Crystalline Solids

regular, repeating 3D arrangements of atoms and/or molecules

Amorphous Solids

disordered structure with no defined pattern

Crystal Lattice/Crystal Structure

points used to denote positions of atoms/molecules

Unit cell

smallest repeating unit of crystal structure

Types of Crystalline solids

Atomic
Ionic
Molecular

Atomic Solids

atoms at lattice points

Metallic Solids

metal atoms held together by clouds of ve-
high melting point, shiny, conductive (Au)

Ionic Solids

Ions at lattice points
brittle, conductive, high melting point

ex. NaCl(s)

Molecular Solids

covalently bonded molecules at lattice points
poor conductivity, low melting point, hard, low density
ex. H2O(S)

Network Covalent Solids

nonmetal atoms at lattice points
poor conductivity, low melting points, very hard

Unit cell lattice points

represent atoms/ions/molecules aka Spheres

Net number of atoms/spheres

total # of atoms contained within the invisible borders of the unit cell

Types of Unit Cells

Simple cubic
Body-centered cubic(bcc)
Face-centered cubic (fcc)

Closest packing structures

arrangement of atoms in a crystalline solid which assumes spheres are as close to each other as possible

Type of packed structres

Hexagonal Closest packed (bcc)(hcp)
Cubic closest packed(fcc)(ccp)

Deposition

gas to solid

sublimation

solid to gas

condensation

gas to liquid

Nonpolar (even electronegativity) means what forces

dispersion

Polar(uneven) compound has what forces

dispersion and dipole

H-F, H-O, H-N

dispersion, dipole, H

C-H bonds only have what force

dispersion

If K > 1, mostly

productsI

If K<1, mostly

reactants