Glossary of Chem Exam 2

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molecule made up of 2 atoms
chemical formulas that indicate the actual numbers and types of atoms in a molecule
molecular formulas
chemical formulas that give on the relative number of atoms of each type in a molecule
empirical formulas
sum of atomic weights of each substance in its formula
formula weight
mass of the collection of atoms represented by the chemical formula for a molecule
molecular weight
each of the atoms in the formula, represented by the chemical formula of the substance
formula unit
percentage by mass contributed by each element in a substance
percentage composition
(num of atoms of element)(atomic weight of element)/formula weight
percentage composition
amount of matter that contains as many objects as the number of atoms in exactly 12g of isotopically pure 12C
number of atoms in exactly 12g of isotopically pure 12C
Avagadro's number
mass of a substance in g/mol; always numerically equal to formula weight
molar mass
based on observation and experiment
angles made by the lines joining the nuclei of the atoms in the molecule
bond angles
AB2 bond angle
180 or bent
AB3 bond angle
AB3 name
trigonal planar
AB4 bond angle
AB5 bond angle
3 are 120, 2 are 90
AB6 bond angle
AB4 name
AB5 name
trigonal bypyramidal
AB6 name
region in which electron will most likely be found
electron domain
best arrangement of a given number of electron domains??
the one that minimizes the repulsions among them
arrangement of electon domains about the central atomof an ABn molecule or ion
electron domain geometry
arrangement of only the atoms in a molecule or ion
molecular geometry
step 1 of VSEPR
draw lewis structure and count total number of electron domains around central atom; each nonbonding pair, single, double, or triple bond counts as a domain
step 2 of VSEPR
determine electron domain geometry by arranging the electron domains about the central atom so that the repulsions among them are minimized
step 3 of VSEPR
use arrangement of bonded atoms to determine molecular geometry
electron domains for nonbonding pairs exert_____ repulsive forces on adjacent electron domains, and thus tend to ______ bond angles
greater, compress
electron domains for ____ bonds exert a greater repulsive force on adjacent electrons than do electron domains for ____ bonds
multiple; single
run vertical, 90 to equatorial
axial positions
run horizontal
equatorial positions
domains for nonbonding pairs exert ______ repulsions than those from bonding pairs
domains from nonbonding pairs always occupy these postions in a trigonal bypyramid
measure of how equally the electrons in a bond are shared between the two atoms of the bond
bond polarity
as the difference in electronegativity between two atoms increases, so does the_____
bond polarity
quantitative measure of the amount of charge seperation in the molecule
dipole moment
the dipole moment depends on both the
polarities of individual bonds and the geometry of the molecule
the dipole moment that is due only to the two atoms in that bond
bond dipole
overall dipole moment of a polyatomic molecule is the
vector of the sum of its bond dipoles
if overall dipole moment is zero, then
the bond is nonpolar
provides a simple means for predicting the shapes of molecules
VSEPR model
model of chemical bonding in which an electron pair bond is formed between two atoms by the overlap of orbitals on the two atoms
valence bond theory
share the same region of space
orbital that results from the mixing of different kinds of atomic orbitals on the same atom
hybrid orbital
mixing of different types of atomic orbitals to produce set of quivalent hybrid orbitals
covalent bond in which electron density is concentrated along the internuclear axis
sigma bonds
covalent bond in which electron density is concentrated above and below line joining the bonded atoms
pi bond
double bonds have this many sigma and pi, triple bonds have this many
1 sig 1 pi, 1 sig 2 pi
sigma and pi electrons are associated totally with the two atoms that form the bond
electrons are spread over a number of atoms in a molecule rather than localized between a pair of atoms; occur when there are resonance structures
forces that exist between molecules
intermolecular forces
phase in which molecules are solid/liquid
condensed phase
solids that possess highly ordered structures
the state of a substance depends largely on the:
balance between the kinetic energies of the particles and the interparticle energies of attraction
keep the particles apart and moving
kinetic energies
interparticle attractions tend to:
draw the particles together
intermolecular attractive forces that exist between neutral molecules
van der waals forces
exist between an ion and the partial charge on the end of a polar molecule
ion-dipole force
magnitude of ion-dipole attraction ______ as either the charge of the ion or the magnitude of the dipole moment increases
neutral polar molecules attract wach other when the positive end of one molecule is near the negative end of another, overall affect is a net attraction
dipole-dipole forces
for molecules of approximately equal mass and size, the strenghts of intermolecular attractions ----- with increasing polarity
boiling point ______as the dipole moment increases
for molecules of comparable polarity, those with _______ molecular volumes generally experience higher dipole-dipole attractive forces
instantaneous force of dipoles, significant only when molecules are very close
london dispersion forces
esae with which the electron distribution in a molecule is distorted
more polarizable molecules have ______ dispersion forces
strength of dispersion forces tends to ______ with increasing molecular weight
liquid or solid in gas state
a force that moves something in a given direction; measure of the force exerted on a unit area, force/area
si unit of pressure
10 to the fifth pascals
inverted glass tube more than 760 mm long
Pressure sufficient to support a column of mercury
standard atmospheric pressure, 760 mmHg
the volume of a fixed quantity of gas maintained at constant temp is inversely proportional to the pressure
boyle's law
the volume of a fixed amount of gas maintained at constant pressure is directly proportional to its absolute temp
charle's law
at a given temp and pressure, the volumes of gases that react with one another are in the ratios of small whole numbers
law of combining volumes
equal volumes of gases at the same temp and pressure contain equal numbers of molecules
avagadro's hypothesis
volume of a gas maintained at a constant temp and pressure is directly proportional to the number of moles of the gas
avagadro's law
hypothetical gas whose pressure, volume, and temp behaviour is completely described by the ideal gas equation
ideal gas
standard temp and pressure
1 atm and 0 C
volume occupied by one mole of ideal gas at STP
molar volume
the total pressure of a mixture of gases equals the sum of pressures that each would exert if it were present alone
Dalton's Law of partial pressures
pressure exerted by a particular component of a mixture of gases
partial pressure
Kinetic molecular theory, 5 key postulates
1. straight line motion, random direction
2.molecules are small (farther apart)
3. no intermolecular forces (cannot attract nor repel)
4. elastic collisions
5. mean kinetic energy is directly proportional to temp (in K)
speed of a molecule possessing average kinetic energy
root mean square speed
escape of gas molecules through a tiny hole into an evacuated space
spread of one substance throughout a space or throughout a second substance
effusion rate of a gas is inversely proportional to square root of its molar mass
graham's law
distance travelled by a molecule between collisions
mean free path
deviations from ideal behavior _____ as temp decreases
real molecues have:
finite volumes and do attract one another

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