AP Chemistry Exam Study Guide

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covalent bonds
elements may combine to form compounds and attain a noble gas configuration
molecules
compounds composed of covalently bonded groups
octet rule
all atoms try to attain noble gas configuration through having 8 electrons around atom
molecular orbit
single electrons create magnetic fields while, cancel it
formal charge
count all electrons not used for bonding by the atom, count half of the atom's bonding electrons, add steps 1 and 2, subtract the assigned electrons from valence electrons (must equal charge of ion, lowest formal charge is best structure of use)
resonance structures
where you can construct multiple lewis dot structures
electronegativity
increases from bottom to top and left to right
delta EN
atom with largest EN - atom with smallest EN (closer to 0 means nonpolar)
bond order
number of bonds divided by number of the element
bond strength
the greater the bond order, the shorter the bond length
types of shapes
linear, linear triatomic, planar triangle, tetrahedron, trigonal bipyramid, octahedron
Determining Polarity
symmetrical shape is nonpolar, nonsymmetrical is polar if bonds are polar, multiple types of atoms attached to a central atom is polar
single bond, double bond, triple bond
one sigma, one sigma and one pi, one sigma and two pi
hybrid orbital
set of orbitals with identical properties formed from the combination of 2 or more different orbitals with different energies
Determining Hybridization
use steric number calculation (number of atoms bonded + lone pairs) 4=sp3 3=sp2 2=sp
empirical formula
percent to mass, mass to mole, divide by small, multiply until whole
electron configuration
allows scientists to determine the number of electrons that a representative metal will lose
driving forces
formations of water, weak electrolyte precipitate gas are the main driving forces of chemical reactions
Gas Laws
Boyle's: P1V1=P2V2
Charles': V1/T1=V2/T2
Gay-Lussac's: P1/T1=P2/T2
Avogadro's: n1/V1/=n2/V2
Ideal: PV=nRT
STP
standard temperature pressure, allows for P=1.00atm and T=273K
Density (gas laws)
nP/RT
kinetic molecular theory
gases consist of molecules or atoms in continuous motion, collisions between them are elastic, volume occupied by these is small, attractive or repulsive forces between these are negligible, and average kinetic energy of these are proportional to the kelvin temperature of the gas
graham's law of effusion
effusion
more collisions of a gas to a wall, the higher the probability that it will hit pinhole to go through
diffusion
movement of one gas to a container that is already filled with gas
kinetic energy
average kinetic energy is higher when there is a higher temperature and vice versa
real gas/ideal gas
gases have no volume and exhibit no attractive or repulsive forces, as it is cooled/compressed the distance between particles decreases

increased volume and increased temperature
Dalton's law of partial pressures
when 2 gases are mixed together, the gas particles tend to act independently of each other
atoms on same plane
means that they are all connected together and there are no lone pairs
largest dipole moment
means the one with the highest difference in charges
net ionic equation
not used to determine what molecules are soluble
polar molecules
in a gaseous state, they show little attraction for each other because they are so far apart
how gas goes to liquid
attractive forces must overcome the kinetic energy of the moving gas molecule
intermolecular forces
dipole-dipole, London forces, Hydrogen bonding
London forces
very weak attractive forces because of momentary unequal distribution of electrons around an atom
Dipole-dipole forces
attraction between the partial positive end of one dipole and the partial negative end of another dipolar molecule
Hydrogen bonding
very strong dipole-dipole attractive forces observed exclusively in compounds that have an F, N, O bonded directly to a hydrogen atom
surface tension
due to an increase in the attractive forces between molecules at the surface of a liquid compared to the forces between the molecules in the center, or bulk, of the liquid
cohesive vs adhesive forces
attractions between identical molecules in the liquid/attractions between different molecules, such as those in the liquid and a flat surface
viscosity
liquid's resistance to flow
substitutional alloy
replace one set of attractive forces with an almost equal set of attractive forces with the added metal
interstitial alloys
incorporate one atom into the existing structure with little change in volume
ionic crystal
has a regular structure, or lattice of alternating positive and negative ions
heating and cooling curve
the temperature of a solid will increase at a constant rate until the solid starts to melt, when melting begins the temperature stops rising and remains constant until all of the solid is converted to liquid, the temperature of the liquid starts increasing at a constant rate until boiling starts, when boiling begins the temperature stops rising and remains constant until all of the liquid had been converted into gas, the temperature of the gas increases at a constant rate
solution
uniform mixture of one or more solutes dissolved in a solvent
solubility
grams per liter of solute that can dissolve in the solvent
solution processes
dissolving ionic compounds, gas mixtures, rates of dissolution
effect of temperature on solubility
molecules tend to move from a lower entropy state to a higher one

solids are more soluble in hot solvents than in cold ones
effect of pressure on solubility
compression increases the frequency with which gas molecules hit the liquid phase and enter it, increasing solubility
forming a solution steps
separate the solute

separate the solvent

combine the separated solvent and solute into a solution
Principles regarding reaction quotient (Q)
if Q does not change with time, the reaction is in a state of equilibrium and Q=Kc

if Q=Kc, the reaction is in a state of equilibrium

if Q<Kc, the reaction will move in the forward reaction (to the right) in order to reach equilibrium

if Q>Kc, the reaction will move in the reverse reaction (to the left) in order to reach equilibrium
ICE Tables
Balanced chemical reaction
Initial Concentration (Molarity)
Change (+x, -x, -2x, etc.)
Equilibrium (0.200+x, 0.250+x, etc.)
Answer
equilibrium constant for gas-phase reactions (Kp)
same calculations as regular equilibrium constant but with pressure values
relationship between Kc and Kp
Kp=Kc(RT)^(moles of products-moles of reactants)
solubility product (Ksp)
Ksp=(product1)^a(product2)^b
Le Chatelier's Principle
whenever a system in dynamic equilibrium is disrupted by changes in chemical concentrations or physical conditions, the system will respond with internal physical and chemical changes to reestablish a new equilibrium state, if possible
Effect of Changing Concentrations
increase reactant=favors products
decrease reactant=favors reactants
increase product=favors reactants
decrease product=favors products
Effect of Pressure and Temperature
refer to page 348
reaction rates
determined by measuring the concentration of one or more chemicals involved in a reaction at different times during the course of a reaction
factors that affect reaction rates
concentration: increasing it will increase reaction rate

temperature: reaction rate is exponentially related to the Kelvin temperature

ability to meet: reactants in the gas phase or solution react most rapidly if very finely divided as in powders or dust

catalyst: a catalyst affords an alternate reaction path with a lower activation energy and results in a higher reaction rate
Rate equation
Rate=k[A]^x[B]^y[V]^z
order of reaction
exponents in the rate law
Calculating rate
solve for x and y by dividing/cancelling rates, substitute x and y into original rate equation, solve
zero order and first order graph
all exponents and of all the reactants are zero/ln[a] vs time
collision theory
rate of a chemical reaction is equal to the collision rate decreased by multiplying by an orientation factor and a minimum energy factor
reaction profile
plots the increase in potential energy of the reactants as they approach, reaching a maximum at the moment of collision, and then the decrease in potential energy as the products recoil
difference between collision theory and transition state theory
collisions between hard spheres/collisions as interactions between reactants that are deformed in the collision process
endothermic vs exothermic in kinetics
potential energy of products is greater than reactants/reverse of previous statement
elementary reactions
mini reactions that add up to the total reaction in the sequence of steps called the reaction mechanism
intermediate catalyst
any chemical species that is part of a mechanism but not part of the balanced equation
standard state
1 atm, 25 degrees Celsius, 1 mole of compound present
law of conservation of energy
energy cannot be created nor destroyed
first law of thermodynamics
energy is always conserved deltaE= q + w
work
force applied to an object as it moves a certain distance work= -PdeltaV
Hess's Law
if the coefficients of a chemical equation are all multiplied by a constant, the standard heat of reaction is multiplied by the same constant, if 2 or more equations are added together to obtain an overall reaction, the heats of these equations are also added to give the heat of the overall reaction
entropy
increase in the number of particles increases entropy, the more the particles are able to move around, (water in ice has least entropy, water as a gas has highest entropy)
temperature in relation to entropy
decrease in temperature lowers entropy
second law of thermodynamics
any physical or chemical change must result in an increase in the entropy of the universe
relationships between Gibb's law and entropy
refer to page 403
thermodynamically favorable
occurs without the need for the additional energy input after the reactants are mixed and the reaction initiated
free energy and equilibrium
if K < 1 the reaction will move in the reverse direction and vv
oxidation and reduction
loss of electrons/gain of electrons
oxidation number rules
numbers of all atoms add up to charge of the atom, molecule, or ion/oxidation of an alkali metal is +1, then +2, then +3/oxidation number for hydrogen is +1, and fluorine is -1/oxygen is -2, halogen is -1/nonmetal group in VIA is -2
balancing redox reactions
refer to page 422
galvanic cell
used to harness the energy of spontaneous redox reactions, flow of charge is carried by electrons in wires and by ions through the solutions and salt bridge
quantitative electrochemistry
1 coulomb = 1 ampere * 1 second
1 mole e^- = 96,485 coulombs
thermodynamically favorable in electrochemistry
if the cell voltage is negative, the reaction is not thermodynamically favorable, and should be reversed to construct a galvanic cell
standard reduction potentials
the standard cell voltage is the difference between the electric potentials (voltages) of the cathode and anode
standard cell voltages and equilibrium
if the 2 electrodes of a galvanic cell are connected so that the electrons flow freely, the reaction will proceed to equilibrium (you can solve for the equilibrium constant through the other standard cell voltage equation)
Arrhenius theory
when an acid is dissolved in water, the reaction may be written in 2 different forms, bases could be considered to be substances that increase the hydroxide ion concentration when dissolved in water
strong and weak acids order
refer to page 452-453
bases
all metal hydroxides are strong bases, all bases related to ammonia are weak bases
neutralization reactions
reactions between acids and bases
pH/pOH
pH=-log[H+]/pOH=-log[OH-]
Equilibrium expressions for acids and bases
K=[H+][OH-]
pKw=pH + pOH
Acid and Base Calculations
refer to page 466
Titration Curves
start of titration, where the solution contains only one acid or base

the region where the titrant is added up to the equivalence point, and the solution now contains a mixture of unreacted sample and products

the equivalence point, where all of the reactant has been converted into a product

the region after the equivalence point, where the solution contains product and excess titrant