Quicksheets Gen Chem Flashcards
how to calculate moles
moles = mass of sample/ molar mass
A =
A = mass number = number of protons
Z =
Z = atomic number = number of protons + neutrons
Planck’s quantum theory
energy emitted as electromagnetic radiation from matter exists in discrete bundles called quanta
Bohr’s model of the atom–how to calculate the energy of an electron
E = -Rh/n^2 Energy = -(Rydberg constant)/(principle quantum number^2) Rydberg constant = 2.18e-18J
equation to find the electromagnetic energy of photons
E = hc/λ Energy = (planck’s constant)(speed of light)/(wavelength)
Balmer series
n>2 to n = 2 Visible: 400-800 nm
Lyman series correspond to
n >1 to n = 1 UV: 90-125 nm
Heisenberg uncertainty principle
it is impossible to determine with perfect accuracy the momentum and the position of an electron simultaneously
principle quantum number (n)
the larger the integer value of n, the higher the energy level and radius of the electron’s orbit; max # of electrons in energy level n is 2n^2
azimuthal quantum number (l)
subshells l = 0,1,2,3 s,p,d,f max number of electrons that can exist w/in a subshell = 4l + 2
Exceptions to the octet rule (5)
H(2), He(2), Li(2), Be(4), B(6) and atoms found in or beyond the 3rd period
magnetic quantum # (ml)
the particular orbital w/in a sub shell where an electron is highly likely to be found at a given point in time
spin quantum # (ms)
the spin of a particle is its intrinsic angular momentum and is a characteristic of the particle, like its charge
Hund’s rule
orbitals are filled such that there are a max # of half-filled orbitals w/ parallel spins
polar covalent bond
bonding not shared equally; pulled toward more electronegative atom
regions of electron density: 2 Example: BeCl3 has ___ shape has ___ angle(s)
linear shape 180˚ angles
regions of electron density: 3 Example: BH3 has ___ shape has ___ angle(s)
trigonal planar shape 120˚ angles
regions of electron density: 4 Example: CH4 has ___ shape has ___ angle(s)
tetrahedral shape 109.5˚ angles
regions of electron density: 5 Example: PCl5 has ___ shape has ___ angle(s)
trigonal bipyramidal shape 90, 120, 180˚ angles
regions of electron density: 6 Example: SF6 has ___ shape has ___ angle(s)
octahedral shape 90˚, 180˚ angles
lewis acid
accepts electrons
lewis base
donates electrons
ligands
coordinate bonding attaches ion/molecule with metal atom
describe coordinate covalent bonds
covalent bonds in which both electrons in the bond came from the same starting atom
describe chelation
when the central cation can be bonded to the same ligand in multiple places; it generally requires large organic ligands that can double back to form a second (or even 3rd bond) with the central cation
chelation therapy is used to
often used to sequester toxic metals (lead, arsenic, mercury)
Describe what happens in hydrogen bonding
The partial positive charge of the H atom interacts with the partial negative charge located on the electronegative atoms (FON) or nearby molecules
describe how dipole-dipole interactions occur
polar molecules orient themselves such that the positive region of one molecule is close to the negative region of another molecule
dispersion forces
the bonding electrons in covalent bonds may appear to be equally shared b/t 2 atoms, but at any particular point in time they will be located randomly through the orbital permitting the unequal sharing of electrons, causing transient polarization and counterpolarization of the electron clouds of neighboring molecules, inducing the formation of more dipoles
a mole is…
the amount of substance that contains the same # of particles that are found in a 12 g sample of carbon-12
molecular/formula weight is measured in
amu per molecule (formula unit)
molar mass is measured in
grams per mole
What happens in combustion reactions
a fuel (like a hydrocarbon) is reacted with an oxidant (like oxygen) to produce an oxide and water CH4(g) + 2O2(g) -> CO2(g) + 2H2O (g)
What happens in combination reactions
two or more reactants form one product S(s) + O2(g) -> SO2(g)
What happens in decomposition reactions
a compound breaks down into 2 or more substances, usually as a result of heating or electrolysis 2HgO(s) -> 2 Hg(l) + O2(g)
What happens in Single-displacement rxns
an atom (or ion) of one compound is replaced by an atom of another element Zn(s) + CuSO4(aq) –> Cu(s) + ZnSO4(aq)
What happens in Double-displacement rxns
aka metathesis rxns elements from 2 different compounds displace each other to form two new compounds CaCl2(aq) + 2 AgNO3 (aq) –> Ca(NO3)2 (aq) + 2 AgCl(s)
Net ionic equations show…
show only the species that actually participate in the reaction (doesn’t show spectator ions) For example, in the reaction of: Zn(s) + Cu2+(aq) + SO4^2-(aq) –> Cu(s) + Zn^2+ (aq) + SO4^2-(aq) Spectator ion = SO4^2- Net ionic equation: Zn(s) + Cu^2+(aq) –> Cu(s) + Zn^2+(aq)
What happens in Neutralization reactions
These are specific double-displacement rxns that occur when an acid reacts with a base to produce a solution of a salt (and usually water) Hcl(aq) + NaOH(aq) –> NaCl(aq) + H2O(l)
Factors affecting reaction rates (4)
reactant concentrations, temperature, medium, catalysts [conc],medium, temp, catalyst
What do catalysts do
catalysts increase reaction rate w/o being consumed; do so by lowering the activation energy
Law of mass action states that
aA + bB cC + dD Kc = [C]^c[D]^d/[A]^a[B]^b Kc = equilibrium constant
What happens when Keq >>1
an equilibrium mixture contains very little of the reactants compared to the products
What happens when Keq << 1
an equilibrium mixture contains very little of the products compared to the reactants
What factors affect Le Chatelier’s principle?
stresses include concentration, pressure, volume, or temperature
A + B C + heat what will make it shift to the right in terms of concentration, volume, pressure, and temp?
Right shift = * more A or B added * C taken away * if pressure is applied or volume is reduced * If temp is reduced
A + B C + heat what will make it shift to the left in terms of concentration, volume, pressure, and temp?
Left shift = * If more C is added * If A or B is taken away * If pressure is reduced or volume is increased * If temp is increased
What does the law of conservation of energy say?
It dictates that energy can be neither created nor destroyed, but that all thermal, chemical, potential, and kinetic energies are interconvertible
Describe an isolated system
in an isolated system, there is no exchange of energy/matter with the environment
bomb calorimetry has to do with what kind of system
bomb calorimetry = a nearly isolated system