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MCAT Chemistry

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Absorbtion Spectrum
A dark line spectrum formed when white light is passed through a vaporized element and a few specific wavelengths are absorbed
Bohr Model of the H Atom
1) e- are present only in specific energy states
2) quantum energy is absorbed or emitted to change energy levels
3)Quantum- smallest ammount of energy that can be gained or lost
Ground State
e- is a t it's lowest energy levels as close to nucleus as possible
Excited State
e- absorbs energy + moves to higher energy level above ground state
4 Quantum #'s and Symbols
n=principal energy level
l=sublevel
m=orbital
s=spin
Sublevel e- cpacity
s=2e-
p=6e-
d=10e-
f=14e-
Valence
# of e- in the atom's highest # d shell
Electronegativity Difference
# found by taking th edifference between the e-negativities of 2 atoms. Value determines bond type.
Values differ by 1.7 or more... ionic
Nonpolar Covalent Bond
When the e-neg. diff. is very small(less than .5). 2 bonded atoms share velence e- resulting molec has no electrostatic charge.
Polar Covalent Bond
e-neg. diff. is btwn. .5-1.7 the bonding e- stay closer to more e-neg. atom... shared unequally.
Coordinate Covalent Bond
when both e- in a covalent bond are supplied by one atom
Metallic Bonds
sea of e- surrounding positive metal ions
Hydrogen Bonding
when H bonds to O,N,F
Octet Rule
atoms tend to gain or lose outer shell e- in order to acheive a noble gas config. of 8 e-
Resonance Structures
more than 1 possible bonding structure
Hybrid Orbitals
2 or more orbitals mix to form identical hybrid orbitals.
triple bond sp
double bond sp2
single bond sp3
Properties of ionc substances
non-conducting
high mp
brittle
low volatility
properties of molecular substances
non-conducting
volatile
many gases
low mp/bp
soft waxy solids
Enthalpy Difference
difference in heat content btwn the products and reactants
Exothermic rxn
∆H is negative
Enthalpy is decreased
Endothermic rxn
∆H is positive
Enthalpy is increased
Hess's Law
∆H for a rxn is the same regardless of the path travelled from reactants to products
Specific Heat
Ammount heat required to raise 1 g of a subst. 1ËšC
Equation for energy change when a fixed mass of a subst. changes temp.
Q=mC∆T
Charle's Law
V1/T1=V2/T2
Boyle's Law
P1V1=P2V2
Combined Gas Law
P1V1/T1=P2V2/T2
Ideal Gas Law
PV=nRT

R=.0802 L-Atm/mol-K
Avogadro's Law
Under same conditions of temp. and pressure; equal volumes of gases contain equal numbers of moles
Vol of one mol of any gas at STP
22.4 L
Heat of Fusion
solid---->liquid
Heat of Vaporization
liquid--->gas
Vapor Pressure
pressure the gas phase exerts on its liquid phase in a closed container.
Molarity
# of moles solute/ liter of solution

M=n/L
3 factors that effect rate of sollubility
pulverizing, stirring, heating
Molality
moles solute/ Kg solvent

m=n/Kg
Gram equivellent weight
ammount of subst. which reacts w/or displaces 1 mole of H+ ions
Normality
# of gram equivelent weights in a liter of solution
5 factors that control rxn rate
nature of reactants
surface area
concentration
temp.
catalyst
Activation Energy
Energy necessary for a rxn to begin. Obtained from the kinetic energy released durign a collsion.
Law of Mass Action
Rate of chemical rxn is proportional to the product of the concentrations of the reactants
Specific rate constant
symbol is "K" in a rate eq. A constant specific to temp. and rxn which is part of every rate eq.
2 driving forces of rxns
Increased entropy- (disorder)
decreased enthalpy-(heat)
Second law of thermodynamics
Entropy of univ. increases for any spontaneous process
Free energy change ∆G
property which reflects a systems capacity to do useful work
∆G=∆H-T∆S
∆G negative=spontaneous
Solubility product constant
an equil. exists in a saturated soln. btwn. dissolved and undissolved solute "Ksp" is the equil constant for this rxn.
KspAgCl= [Ag+][Cl-]
Arhenius Theory
an acid yields protons in soln. (H+)
a base yields OH-
Bronstead Theory
an acid is a proton donor
a base is a proton acceptor
Lewis theory
ana acid is an e- acceptor
a base is an e- pair donor
Equation for finding vol or molarity when given vol or molarity
MaxVa=MbxVb
Anode
A positively charged electrode which attracts anions where OXIDATION takes place
Cathode
A negatively charged electrode which attracts cations where REDUCTION occurs
Electrode Potential
a measure in volts of the tendencyof atoms to gain or lose e-.
Spontaneousredox rxn
add the electrode potenetials of the 2 half rxns. If the result is positive, the rxn is spontaneous; if negative the rxn is not spontaneous
Ether
R-O-R'
Amine
R-NH2
Ester
R-O-C=O-R
Amino Acid
H2N-CRH-COOH
Alpha Particle
Helium nucleus
ejection reduces atomic # by 2 amu and atomic weight by 4 amu.
Beta Particle
e- ejected from a nucleus. Neutron decays to proton.
Increases atomic # by 1
high velocity
low energy
Gamma (positron) Radiation
doesn't change mass or charge
high energy
travels at speed of light
Transmutation
Conversion of an element to a new element due to a change in # of protons

alpha or beta decay
Fission
breakdown of heavy nuclei into lighter nuclei

nuclear power
Fussion
joining of lighter nuclei to form heavier nuclei.

Sun's Power
Conversion from
celcius-->farenheit
ËšF=(1.8xËšC)+32
Conversion from
celius--->kelvin
K=ËšC+273
Energy
ability to do work; it is released or absorbed during chem. rxn's in the form of heat, light, electricity
Matter
A susbstance that occupies space and has mass
Density
D=(mass)(volume)
Element
substance composed of identical atoms
Compound
subst. composed of 2 or more elements chemically combined
NaCl. NH3, H2O
Mixture
A combination of subst. held together by physical means
Dalton's Atomic Theory
1) an element is composed of identical atoms
2)atoms of different elements have diff. properties
3)compounds are atoms of 2 or more elements chem. combined
Law of Conservation of Mass
During a chem. reaction matter is neither created or destroyed
Law of Constant Composition
Cmpnd always contains the same elements combined in the same in the same portions by mass
Law of Multiple Proportions
Same elements may combine to form more than one compound. The ratios are in small whole #'s
Atomic Mass Unit
the mass of a proton or neutron is equal to 1 amu
Atomic #
# of protons in the nucleus of an atom of an element
Mass #
the sum of protons+neutrons in the nucleus of an atom
Isotope
atoms which contain the same # of protons but diff. #'s of neutrons
Molecule
A group of 2 or more atoms held together by chemical bonds
Diatomic Elements
H2,O2,F2,Br2,I2,N2,Cl2
formal charge
charge=
Valence e - 1/2 Nbondinge-Nnonbondinge
percent yield
actual/theoretical
limiting reactants
1)determine moles needed
2)look at eq. determine limiting reagent
isothermal process
temp remains constant
isobaric process
pressure remains constant
adiabatic
no heat exchange
soluble aqueous soln
salts of alkali metals
salts of ammonium
chlorides
bromides
iodides
sulfate ion
insoluble aqueous soln
metal oxides
hydroxides
carbonates
phosphates
sulfites
chiral molecules
non-superimposable images
handedness
stereoisomers
same atomic connections but arrange diff. in space
geometric isomers
differ in arrangement of atoms around double bond
determining absolute configuration at a single chiral center
1)assign priority by atomic number
2)orient the molecule with the lowest priority substituent at the back
3)lowest priority to highest priority

R=clockwise
S=countercockwise
meso compounds
contain chiral centers but are not optically active due to an internal plane of symmetry
specific rotation(alpha)
observed rotation/concentration(g/ml)Xlength(dm)
diastereomers
for any molec with n chiral centers there are 2 to the n sterioisomers
conformational isomers
compuonds that differ only by rotation about one or more single bonds
energy scale of diff conformations
highest energy=totally eclipsed, eclipsed, gauche, anti
good leaving groups
weak bases, halides
SN1
2 steps
dissociation of a molecule into a carbocation and a good leaving group
combination of carbocation with a good nucleophile
slow step is rate determining step
favored in polar protic solvents
racemic products
favored with use of bulky nucleophile
rate=k[RX]
SN2
single step rxn
nucleophile performs backside attack and replaces leaving group
favored in polar aprotic solvents
rate=K[Nu][RX]
optically active inverted products
Alkyne reduced to cis alkene
H2, Pd/BaSO4, quinoline
Alkyne reduced to trans alkene
Na, NH3
activating, ortho/para directing(e- donating)
NH2, NR2, NHCOR, OR, OCOR, R
deactivating ortho/para directing (weak e- withdrawing)
F, Cl, Br, I
deactivating meta directing (e- withdrawing)
NO2, SO3H, carbonyl cmpnds, COOH, COOR, COR, CHO
primary alcohols oxidize to
aldehydes--->carboxylic acids
secondary alcohols oxidize to
ketones
ways to stabalize the negative charge and thus increase acidity are
1)e- withdrawing groups(halides)
2)groups that allow more resonance stabilization (benzyl or allyl substituents)
order fo reactivityof carboxylic acid derivatives
acyl halides, anhydrides, esters, amides
proteins
primary structure
describes the amino acid sequence and covalent bonds
cystine
proteins
secondary structure
describes hydrogen bonding
alpha helix and beta pleated sheets
keratin in hair
proteins
tertiary structure
3 dimensional shape of the protein
myglobin
collagen
proteins
quaternary structure
arrangement of polypeptide sub units
hemoglobin

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