PCAT Chemistry

coordinate-covalent bond
shared pair comes from the lone pair of one of the atoms
Factors affecting reaction rate

reactant concentrations

temperature

meduum

catalysts

Isolated system
cannot exchange energy or matter with ssurroundings
closed system
can exchange energy but not matter with surroundings
open system
can exchange matter and energy with surroundings
adiabatic process

one where no heat exchange occurs; temperature of material can change

 

(isothermal when temperature of system remains constant)

DG

 DG°= 

DG° + RT ln Q

-RT ln Keq

STP

Gases

0°C, 1 atm, 22.4L

Standard conditions

enthalpy, entropy, Gibbs, and voltage

25°C

Boyles Law
PV=k
Law of Charles and Gay-Lussac
V/T-k
Avagadro’s principle
n/V=k
Dalton’s Law

Total P = sum of partial pressures

PA=PTXA

XA=nA/nT

KE
=1/2mv2=3/2kT
Graham’s law of diffusion and effusion
r1/r2=(MM2/MM1)1/2

crystalline solids

(vs. amorphous)

ordered structure; specific 3D arrangement 

Ionic: aggregates of +/- ions; no discrete molecules

Metallic: metal atoms packed together closely

Colligative properties

physical properties derived soley from the number or particles present

 

Freezing-point depression (DT=Kfm <--molality)

Boiling-point elevation (DT=Kbm)

Osmotic Pressure (P = MRT)

Vapor-Pressure Lowering (Raoult’s Law…PA=XAA) (DP =P°A-PA=XBA)


 

-ous vs -ic

-ide

-ite vs -ate

hypo- and per-

bi-

less vs greater charge

monatomic anion

less and more oxyanions

even less and even more anions

one hydrogen (vs dihydrogen)

Ion product and solubility product constant

=[A]m[B]n

I.P. with respect to initial concentrations (not eq.)

Ksp represents equilibrium or saturated sol. 

 

solubility
maximum amount of that substance that can be dissolved
Alpha decay
emission of 42He
Beta decay

b– emitts electron: neutron decays into proton and e

b+ emitts positron: proton splits into a positron and neutron

gamma decay
emitts g-particle; just lower energy without changing mass or charge
T1/2
time it takes for half of sample to decay
exponential decay

rate at which nuclei decay proportional to number that remain –> Dn/Dt = -ln


n = n0elt


l=ln 2/T1/2=0.693/T1/2

Leaving Groups

provide stable anion on its own, weak bases;

have strong conjugate acids

 

Good: Halides (except F), water, TSO

 

Moderate: NH3

 

Poor: HO, RO

 

Extremely poor: NH2, H, R

Protic Solvents

With dissociable (acidic) H+ (water, alcohol, formic acid, ammonia)

Stabilize nucleophile

Favor SN1 

aprotic solvents

lack acidic hydrogen, no H bonding

lack H-O or H-N bonds

(ethers, ketones, halogenated hydrocarbonds)

favor Sn2 reactions

Nucleophiles

Less EN–> hold electrons less tight

More linear/smaller –> less sterically hindered

Polarizability (increases down table)

 

Very good: HS, I, RS

Good: Br, HO, RO, CN

Moderate: NH3, Cl, F, RCO2

Weak: H2O, ROH

Very weak: RCO2H

Acid Strength

More stable conjugate base = stronger acid

“-” prefer to rest on: 1) larger atom to spread charge

2) EN atoms–> ion stability

Resonance stabilization

Neighboring EN groups pull some electron density alleviating atom

 

Strong acids = strong electrolytes (HCL, HBr, HI, HClO4, HNO3, H2SO4)

 

 

Activating Groups

increase rate by stabilizing cationic intermediate by donating electrons to ring system

toluene, phenol, aniline (NH2)

 

Deactivating groups

decrease reaction rate by withdrawing electron density from ortho and para positions leaving meta positions as least unreactive

nitrobenzene, benzaldehyde, ketones, esters, carboxylic acids, sulfo, cyano 

Ortho/Para directors

groups w/ unshared pairs of electrons (donate to pi system)

Activators: NH2, OH, OR; weak ones: R

Halogens (deactivators): EN so draw electron density, but have unshared pair of electrons

Meta directors

non-halogen groups with EN atoms

Deactivating groups: NO2, NR3+, CX3 (Trihalides); CN2, SO3H, CO2H, COOR, aldehydes, ketones

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