AP chemistry do not forget

basics to getting a 3

density

mass divided by volume; use this in stoich. problems to convert between mass and volume

coulomb’s law

the attractive force between an atom’s protons and electrons is directly proportional to the number of protons and indirectly proportional to the square of the distance between the nucleus and the electrons

percent composition by mass for a pure compound

does NOT change

mass spectroscopy graphs depict

atomic masses and relative abundances of isotopes

when reading a PES graph, the high the peak…

the more electrons there are in that sublevel

when reading a PES graph, a larger binding energy…

means that the electrons are closer to the nucleus

electron configuration order

1s² 2s² 2p^6 3p^6 4s² 3d^10 4p^6

elements in the same group (vertical columns)

have similar chemical and physical properties

percent yield

experimental mass divided by theoretical mass

percent error

(experimental - theoretical)/theoretical

diatomic elements

H2, O2, N2, Cl2, Br2, I2, F2

covalent bonds

formed between two nonmetals sharing electrons

ionic bonds

formed when a metal transfers electrons to a nonmetal and the opposite charges attract

the greater electronegativity difference between 2 atoms…

the more polar the bonds becomes

empirical formula

simplest whole number ratio of the moles (or numbers in the compound) (percent to mass, mass to mole, divide by small, times until whole)

molecular formula

whole number multiple of the empirical ratio

the amount of product for a reaction is determined by

the limiting reactant

carbon can make a total of

4 bonds in a compound

bond angle: 4 domains

109.5 degrees

bond angle: 3 domains

120 degrees

bond angle: 2 domains

180 degrees

hybrid orbitals: 4 domains

sp³

hybrid orbitals: 3 domains

sp²

hybrid orbitals: 2 domains

sp

asymmetrical molecules

dipoles do NOT cancel = polar molecule

symmetrical molecules

dipoles cancel = nonpolar molecule

single bond

sigma

double bond

sigma and pi bond

triple bond

sigma and 2 pi bonds

lattice energy

the energy to break an ionic bond in a compound. increases as the ion’s charge increases. decreases as the radii of the ions increase

formal charge

involves comparing the number of valence electrons an atom has to the humber of electrons around it in the Lewis structure (bonded electrons are given evenly to the two bonded atoms)

IMF’s from weakest to strongest

london dispersion, dipole-dipole, hydrogen bonding, ion-dipole

london dispersion forces

all molecules have this, this force gets stronger as the molecule is larger. larger electron cloud = more LD = more polarizable

dipole-dipole forces

all polar molecules have this force, and it gets stronger as the molecule is more polar

hydrogen bonds

between F/O/N in one compound to a hydrogen that’s already bonded to a F/O/N in another compound

boiling and melting points increase as

IMF’s increase

vapor pressure and volatility decrease as

IMF’s increase

molecular solids

have low boiling/melting points, and do not conduct electricity

when a molecular solid melts/boils

it is the IMF’s between the molecules that break, not the covalent bonds

SiO2 (quartz) and diamonds

are covalent network solids and have very high boiling/melting points

ionic solids

have high melting/boiling points, and don’t conduct electricity as solid but DO as when dissolved or (aq.)

metallic “bonds”

between metals only, and ALWAYS conduct electricity. their hardness varies

interstitial alloys

when a smaller atom fits into the gaps between larger atoms of a metallic crystal

substitutional alloys

when the radii of the metals are similar in size and are substituted into the crystal lattice

gas mixtures are homogenous because…

of the constant random motion of the particles

gases are compressible because…

of the large spaces between the particles

gas pressure is caused by…

the collisions of particles within the walls of the container (more collisions = more pressure)

P and V are inversely related…

doubling the volume of a container will cut the pressure of the gas in half (P1/V1 = P2/V2)

T and V are directly related…

if you heat a balloon, it will expand (T1V1 = T2V2)

T and P are directly related…

if you heat a rigid container, the pressure of the gas will increase (T1P1 = T2P2)

ideal gas law

PV=nRT

one mole of an ideal gas

22.4 liters only at STP

gas pressure and number of moles are directly related…

if you double the mole of gas in a container, the pressure will double

molar mass

dRT/P, d stands for density in units of g/L

the more molar mass a gas has….

the slower it moves at a given temperature

temperature

average kinetic energy

when collecting a gas by water displacement

P total = P dry gas + P water vapor

distillation

separates mixtures based on differences in boiling point (boiling points depend on the strength of IMFs)

chromatography

separates mixtures based on differences in polarity

in paper chromatography

the component most similar in polarity to the “mobile phase” moves up the farthest

“like dissolves like”

solubility in solvents of differing polarities

beer’s law

the darker the solution, the more it absorbs light. absorbance is directly proportional to the concentration of the solute

compounds can be separated into

elements by chemical changes

mixtures can be separated by

physical changes

mass is conserved during

chemical and physical changes

coefficients of a balanced chemical equation can

represent moles, molecules, formula units, or atoms; NOT mass

acids transfer

protons to bases

redox reactions

transfer of electrons, OIL RIG

OIL RIG

oxidation is loss of electrons, reduction is gain of electrons

oxidation numbers

H = +1 (except in a hydride when it is -1) and O = -2 (except in a peroxide when it is -1)

group 1, nitrate, and ammonium are

soluble, assume all others are not

in order for a reaction to occur

particles must collide at the correct orientation and with a minimum energy to break bonds (activation energy)

rate law for an elementary step

2A + B = C + D, rate = k(A)²(B)

1st order rate constant (k) units

s^-1

2nd order rate constant (k) units

M^-1 s^-1

zero order graph

linear for (A) vs time

1st order graph

linear for ln(A) vs time

2nd order graph

linear for 1/(A) vs time

k on graph =

absolute value of slope

½ life for a 1st order process

t1/2 = 0.693/k

the higher the activation energy

the slower the reaction

ways to speed up a reaction

1. add a catalyst, lowers the activation energy

2. increase reactant concentration, more collisions

3. increase surface area, more collisions

4. increase pressure of gases, increases the concentration of the gas so there are more collisions

5. increase temperature, more collisions and more of them have the minimum activation energy

the slowest step (rate determining step) will

dictate the speed of the reaction, and this step will determine the rate law

intermediates

produced in one step and used up in a later step

catalysts

are used up in one step, and produced in a later step

temperature remains

constant during a phase change

enthalpy is a state function

path from reactants to products is irrelevant

exothermic reactions

have a negative delta H; heat is removed from the system and given to the surroundings; feels hot; heat is a product; temperature goes up…

endothermic reactions

have a positive delta H; heat is removed from the surroundings and give to the system; feels cold; temperature goes down

delta H of the reaction =

summation of delta H of bonds broken minus summation of delta H of bonds formed ( reactant bonds are broken; product bonds are formed)

breaking bonds is

endothermic (positive delta H)

forming bonds is

exothermic (negative delta H)

delta H of a reaction

= delta H of products minus delta H of reactants (don’t forget to multiply by the coefficients)

if a reaction is exothermic

the bonds formed in the products are stronger/more than the reactant bonds

doubling a reaction?

delta H will double

reserving a reaction?

the sign for delta H changes

adding reactions?

add the delta H’s

thermodynamically favorable reactions have

a NEGATIVE delta G

reactions with negative delta H and positive delta S

are ALWAYS thermodynamically favorable… “enthaply and entropy driven”

reactions that increase the number of moles of gas

have a positive delta S