Chem 162 Midterm 1

Bond Order

(bonding + antibonding) / 2

paramagnetic

unpaired electron on M.O. diagram

diamagnetic

paired electron on M.O. diagram; no unpaired

Strong bond = short bond length

Weak bond = long bond length

Order of strongest IMFs (weak - strong)

Dispersion, dipole-dipole, hydrogen bonding, ion bonding

Dispersion

-only for nonpolar molecules

Dipole-dipole

-only for polar molecules

hydrogen-bonding

only if there are Hydrogen atoms on N, O, & F and a lone pair on N, O or F as well

ion-ion

only for negative and positive charges

Weak IMF

-low boiling point b/c easy to break bonds

-low freezing point

-high volatility

-high vapor pressure

-low viscosity

-low surface tension

Strong IMF

-high boiling point b/c hard to break bonds

-high freezing point

-low volatility

-low vapor pressure

-high viscosity

-high surface tension

volatility

easy of evaporation

vapor pressure

how much pressure in gas phase

viscosity

resistance to flow

Ionic Solid

-metal + nonmetal

-ex: NaCl(s), CsCl(s), MgCl2(s)

-high melting points

-water dissolves the solid by forming hydration shells around its parts

molecular solid

-nonmetal + nonmetal

-ex: S8(s), P4(s), CO2(s), P4O10(s)

-low melting points

-POLAR: molecules are held in solid state by hydrogen bonds

-NONPOLAR: of the homo-nuclear diatomic molecules only those of large molar mass are solids @ room temp

metallic solid

-pure metals

-ex: Na(s), Fe(s), Pb(s)

-malleable and high electron-conductivity

-sea of electrons

-conducts electricity

-bonds in the solid state are not directional and all atoms share their valence electrons

WHEN IT'S THE SAME TYPE OF SOLID:

more dispersion = higher boiling point = higher molecular weight

network covalent solid

-infinite lattice structures

-metalloids (neither metals or nonmetals)

-ex: carbon-graphite(s), carbon-diamond, Si, SiO2(molecular network solid because it's a molecule)

-extremely high melting points

-not a specific packing type

-to break solid into pieces, covalent bonds must be broken

atomic solid

-noble gas in solid state

-ex: Ne(s), Ar(s)

Simple Cubic

(1/8) * 8 = 1 atom

52% packing efficiency; only 52% of space is filled

edge = 2r (r = radius)

Face centered cubic (fcc)

every face of cube has 1/2 of a sphere

((1/8) * 8) + ((1/2) * 6) = 4 atoms

74% packing efficiency

e =√8 *r

Body centered cubic (bcc)

full sphere in center of cube

((1/8) * 8) + 1 = 2 atoms

68% packing efficiency

e = 4/√3 *r

Calculate density (mass of atom [s]/volume [cell]) = g/cm³

((# of atoms [depends on type of packing]) * Avogadro's # (1/6.022*10²³)*molar mass)) / e³

like dissolves

-ionic compounds usually dissolve only in polar solvents

-molecular compounds made of polar molecules usually dissolve best in polar solvents

-molecular compounds made of non polar molecules dissolve best in non polar solvents

holes are charge carriers

not electrons (when it comes to doping)

Molarity

moles of solute (mols) / Liters of solution (L)

Molality

moles of solute (mols) / kg of solvent (kg)

mole fraction

moles of solute / (moles of solute + moles of solvent)

Pressure-gas = Kh (henry's constant - atm/M) * molarity (M)

Pressure(gas) * Kh (henry's constant - M/atm) = molarity (M)

in a homonuclear diatomic molecules, s-p mixing occurs when the p-orbitals are 1/2 filled or less than 1/2 filled

more electrons = increased bond strength

low viscosity - fast flow

high IMF - high viscosity

high temp - more flow

high viscosity - slow flow

low IMF - low viscosity

low temp - less flow

Diamond

network solid of carbon atoms. Each carbon atom is covalently bonded to 4 other carbon atoms w/ an sp3 hybridization forming one large molecule

insulator - doesn't conduct electricity

copper

held together by metallic bonding where the atomic orbitals of the valence electrons form a continuous energy band. unfilled valence atomic orbitals form a conduction band of higher energy than the valence electron band

conductor b/c there's no energy gap between valence bond and conduction bond which allows electrons to move into conduction band w/ the energy to move from atom to atom

sodium chloride

chloride ions larger than the sodium ions formed a fcc with atoms at the corners and faces. The ions are not close packed but the cube is expanded to reduce the repulsion

insulator - doesn't conduct electricity when in solid state but will do so in liquid state

carbon dioxide

nonpolar molecule that forms a molecular solid. molecules are held together in the solid by dispersion forces between molecules

insulator - doesn't conduct electricity

steel alloy

consists of iron atoms arranged in close-packed arrangement and contains carbon atoms in some of the holes. called an interstitial alloy bc carbon atoms are in the interstices in iron lattice.

poor conductor

temperature increases = solubility of gas decreases

(less gas in aqueous phase)

q = mass*concentration*∆T

q = n*∆Hfus/∆Hvap

n = # of moles

more valence electrons than metalloid

n type

less valence electrons than metalloid

p type

hexane

nonpolar

water

polar

∆H > 0 means endothermic

∆H < 0 means exothermic

how to find heat of vaporization for substance given graph

slope/8.314