Kaplan General Chemistry Unknown Concepts Flashcards
What are the quantum numbers?
n: energy of shell (rows of the periodic table)
- max number of electrons in a shell: 2n^2
- n^2 orbitals
l: subshell (s,p,d,l)
[0 - (n-1)]
- 4l+2
ml: specifies orbital within a subshell
(-l to l); 2l + 1 values
ms: spin (+/- 1/2)
d orbitals always fill to 5 or 10 over the 4s
What is paramagnetic vs. diamagnetic?
paramagnetic: unpaired electrons; attract material to magnet from parallel spins in electrons
dimagnetic: all paired; repelled by magnets
What is Planck’s relation for energy in terms of frequency and wavelength?
E=hf
E=hc/lambda
What are periods and groups?
periods = rows
groups = columns, same valence shell electron configuration
What is effective nuclear charge Zeff?
net positive charge experienced by electrons in the valence shell
- increases from left to right
Zeff = protons - nonvalence electrons
What are the exceptions to the octet rule?
incomplete octet: H (2), He (2), Li (2), Be (4), B (6)
expanded octet: all elements in period 3 or greater
What are coordinate covalent bonds?
when single atom provides both bonding electrons while the other atom does not contribute any
- Lewis acid base chemistry
What is formal charge?
when atom is surrounded by more or fewer valence electrons than it has in neutral state
= V - Nnonbonding - 1/2Nbonding
= valence electrons - dots - sticks
What is VSPER theory?
3D molecular geometry of covalently bonded molecules; electrons will arrange themselves as far away as possible
nonbonding: more repulsion because they are closer to the nucleus
ELECTRONIC CONFIGS
linear: 2 atoms; 180
trigonal planar: 3 atoms; 120
tetrahedral: 4 atoms; 109.5
trigonal bipyrimidal: 5 atoms; 90, 120, 180
octahedral: 6 atoms; 90, 180
What are the electronic and molecular shapes of CH4, NH3, and H2O?
all three have tetrahedral electronic geometry
CH4: tetrahedral
NH3: trigonal pyramidal
H2O: bent
What are sigma and pi bonds?
sigma: head to head overlap
pi: overlap of two parallel electron clouds
Give the order of the strength of intermolecular forces.
1) ionic bonds
2) covalent bonds
3) hydrogen bonds: H bonded to FON
4) dipole-dipole: oppositely charged ends of polar molecules; negligible in gas phase
- dipole moment = p = qd
5) LDF: present in all atoms and molecules
What are equivalents and normality?
Equivalents (Eq)
- number of moles of reactive units (protons, electrons, or ions) in a substance that reacts with or supplies one mole of H⁺ or OH⁻ in an acid-base reaction, or one mole of electrons in a redox reaction.
- moles substance * n factor (number of reactive units)
- mass of compound * n / molar mass
Normality (N)
- concentration unit expressed as the number of equivalents of solute per liter of solution.
- molarity * n
What is the formula for percent composition?
(mass of element in formula / molar mass) * 100
What is the difference between empirical and molecular formula?
empirical: simplest whole number ratio of elements in a compound
molecular: exact number of atoms in a compound
- normally the same or a multiple of the empirical
How do you determine the limiting reactant?
1) make sure equation is balanced
2) determine molar amounts of each reactant using the coefficients in the equation
3) determine amount of product
How do you name polyatomic anions?
hypochlorite O, chlorite O2, chlorate O3, perchlorate O4
What is the Arrhenius equation?
represents collision theory; rxn rate is proportional to the number of effective collisions (proper orientation and kinetic energy)
rate = Z x f
- Z: total number of collisions
- f: fraction of collisions that are effective
k = Ae^(-Ea/RT)
- low activation energy + high temperature increases k
What is the free energy change of a reaction?
deltaG products - deltaG reactants
- negative means exergonic, energy given off
- positive, endergonic, energy absorbed
How do you affect reaction rate ?
1) increasing the concentration of reactant will increase the reaction rate ~ more effective collisions
2) increasing temperature increases rate ~ more kinetic energy
3) changing the medium can increase or decrease rate, depending on how the reactants interact with it
4) adding a catalyst lowers activation energy
Describe rate laws.
rate = k[A]^x [B]^y
- usually do not match stoich coefficients unless single step mechanism (no int), have to be determined experimentally
- 0 order reactions have constant rate
Describe the graphs of concentration vs. time curve for each order reaction.
0: straight line, slope is -k
- temp and catalyst are the only thing that can change
1: nonlinear; slope of ln [A] is linear and = -k
2: nonlinear; slope of 1/[A] is linear and = k
what is the difference between Q and Keq?
Q: value that relates reactant to product concentrations at any given time during a rxn
Keq: ratio of products to reactants at equilibrium, each being raised to stoich coefficient
- constant with constant temperature
if Q<K, delta G <0, then reaction proceeds forward
if Q = K, delta G = 0, dynamic equilibrium
if Q > K, delta G >0, reaction proceeds in reverse direction
What is Le Chatlier’s principle?
1) increasing concentration of reactants or decreasing products will shift the reaction to the right
2) increasing the pressure on gaseous system (decreasing volume) will shift the rxn towards the side with fewer moles of gas
3) increasing the temperature of an endothermic reaction or decreasing the temperature of an exothermic reaction will shift the reaction to the right
What is the difference between kinetic and thermodynamic products?
kinetic: higher free energy and can form at lower temperatures; form fast
thermodynamic: lower in free energy and are more stable; slower; more spontaneous; higher temperatures
What are isolated, closed, and open systems?
isolated: exchange neither matter nor energy with the environment
closed: can exchange energy but not matter with environment
open: can exchange energy and matter with environment
deltaU (change in internal energy) = Q (heat added) - W (work)
What is isothermal, adiabatic, isobaric and isovolumetric (isochoric)?
isothermal: constant temp
adiabatic: no heat exchange with environment
isobaric: constant pressure
isovolumetric (isochoric): constant volume
What is the difference between temperature and heat?
temp: measure of average kinetic energy of a substance
heat: transfer of energy that results from differences of temperature between two substances
- can enter or leave a system
What is enthalpy?
delta H = H pdts - H reactants
delta H rxn = sum of delta H pdts - sum of delta H reactants
delta H rxn = sum of delta H bonds broken- sum of delta H bonds formed
larger the alkane, the larger the more numerous the combustion products
equivalent to heat (Q) in under constant pressure
Q<0, exothermic, releases heat
Q>0, endothermic, absorbs heat
Q = mc deltaT
- m: mass
- c: specific heat (energy needed to change the temp of 1 g 1 degree)
What is entropy?
degree to which energy has been spread throughout a system or between a system and its surroundings; disorder; maximized at equilibrium
delta S = Qrev / T
- Qrev: heat gained or lost in reversible process
delta S rxn = sum of delta S pdts - sum of delta S reactants
What is the formula for the final temperature of a two-liquid or liquid-solid system ?
cold object gains heat, hot one loses it
qcold = -qhot
calorimetry is an adiabatic process: insulated, so no heat is exchanged with universe, just between the system and the surroundings
What is Gibbs free energy?
delta G<0 = spontaneous, forward, exergonic
delta G = 0, equilibrium
delta G >0, nonspontaneous, reverse, endergonic
delta G = delta H - T delta S
delta G rxn = sum of delta G pdts - sum of delta G reactants
How do you calculate heat of fusion and heat of vaporization?
q = mL
m: mass
L: latent heat = enthalpy of isothermal process (phase change)
What are the STP values for gases?
1 atm = 760 mmHg = 760 torr = 101.325 kPa
22.4 L
273 K = 0 C
PV=nRT
- R: 8.21x10^-2 L atm / mol K
- R: 8.314 J / mol K
**standard state = 25 C = 298 K)
How do you get density using the ideal gas law?
n = mass / molar mass
PV = m/M RT
density = m/V, therefore density = PM/RT
What are special versions of the ideal gas law?
IDEAL: PV = nRT
combined : P1V1/T1 = P2V2/ T2
Avogdro’s: constant temp and pressure
n1/V1 = n2 / V2
Boyle’s: constant temp and moles (inverse curve)
P1V1 = P2V2
Charle’s: constant pressure and moles
V1/T1 = V2 / T2
Gay Lussac’s: constant volume and moles
P1/T1 = P2 / T2
What is Dalton’s law of partial pressures?
individual gas components of a mixture of gases will exert individual pressures in proportion to their mole fractions
- Pa = Xa * PT
What is Henry’s Law?
amount of gas dissolved in solution directly proportional to partial pressure of gas at the surface
[A] = kH * Pa
- kH: Henry’s constant
What assumptions does the kinetic molecular theory make?
gas have negligible volume, do not have IMF, undergo random collisions, collisions are elastic, average kinetic energy of gas particles is directly proportional to temperature
KE = 1/2 mv^2 = 3/2 kB T
- kB: Boltzmann constant
root-mean-square speed = sqrt (3RT/M) ~ average speed of gas molecule
What is Graham’s Law?
gases with lower molar masses will diffuse or effuse faster than gases with higher MM at the same temperature
- diffusion: high to low concentration
- effusion: movement of gas from one compartment to another through small opening under pressure
r1/r2 = sqrt(M2/M1)
- r1/r2: diffusion rates of gases
What is van der Waals equation of state?
correct ideal gas law for IMF and molecular volumes
(P + n^2a/V^2) (V-nb) = nRT
a: attractive
b: big
What are the 7 general solubility rules?
1) all salts containing ammonium (NH4+) and alkali metal (Group 1) are water-soluble
2) all salts containing nitrate (NO3-) and acetate (CH3COO-) anions are water-soluble
3) halides (Cl-, Br-, I-) excluding fluorides and anything with Ag+, Pb2+, and Hg2+, are water-soluble
4) all salts with sulfate ion (SO4 2-) are water-soluble, except Ca2+, Sr2+, Ba2+, and Pb2+
5) all metal oxides are insoluble except the ones formed with alkali metals, ammonium, and CaO, SrO, and BaO
6) all hydroxides are insoluble, except the ones formed with alkali metals, ammonium, Ca2+, Sr2+, and Ba2+
7) all carbonates, phosphates, and sulfides are insoluble with the exception of the ones formed with alkali and ammonium
What are complex ions or coordination compounds?
composed of metallic ions bounded to various neutral compounds and anions = ligands
- increases the solubility of otherwise insoluble ions because it uses pdts from dissolution rxn
- hemoglobin
Kf: equilibrium constant for complex formation; much greater than Ksp
What is percent composition by mass?
(mass of solute/ mass of solution) * 100
What is the difference between molarity and molality?
molarity: moles of solute / L of solvent
molality: moles of solute / kg of solvent
What is the dilution equation?
MiVi = MfVf
(initial and final)
What is solubility product constant and what is its relation to ion product?
Ksp = equilibrium constant of dissociation rxn
IP< Ksp: solution is unsaturated, more solute will dissolve
IP = Ksp; solute is saturated, no change in concentrations
IP > Ksp: supersaturated, precipitate will form
turn each [A] into x, then solve
MX: Ksp = x^2
MX2: Ksp = 4x^3
MX3: Ksp = 27x^4
What is the common ion effect?
reduction of molar solubility when there is ion in solution
What is Raoult’s Law?
presence of other solutes decreases evaporation rate of a solvent without affecting its condensation rate, decreasing vapor pressure (vapor pressure depression)
- as the vapor pressure decreases, temperature required to boil the liquid must be raised (boiling point elevation)
Psolution = Xsolv * Psolv
- Psolution: vapor pressure of solution
- Xa: mole fraction of solvent
- Psolv: vapor pressure of solvent
What is the formula for boiling point elevation ? Freezing point depression?
increase in BP = iKbm
- i: van’t Hoff factor; # of dissolved ions
- Kb: proportionality constant of solvent
- m: molality
freezing point depression = i Kf m
**both give amount that it is raised or lowered, add to original temp **
What is bronsted lowry acid and base? Lewis acid and base?
Bronsted
- acids: donate hydrogen ions
- base: accept hydrogen ions
Lewis
- acid: electron pair acceptors
- base: electron pair donors
What are the naming conventions for acids (ite vs. ate)?
chlorite = ClO2- to chlorous acid = HClO2
chlorate = ClO3- to chloric acid - HClO3
nitrite = NO2- to nitrous acid = HNO2
nitrate = NO3- to nitric acid = HNO3
What is Kw? formula for pH?
10^-14 at 298K
Kw = [H3O+][OH-] = 10 ^-14
Ka, acid x Kb, conjugate base = 10^-14
Kb, base x Ka, conjugate acid = 10^ -14
pH + pOH = 14 at 298K
pH = log 1/[H+]
What is equivalence point? HH equation?
NaVa = NbVb
pH = pKa + log [A-]/[HA]
pOH = pKb + log [B+]/ [BOH]
What is the only thing that alters equilibrium constants?
temperature modifies Gibbs free energy, nothing else does (P, concentration, V)
How do you balance a redox reaction?
separate half reactions
add H+ and H2O to the reaction that needs oxygen
balance charge
multiply reactions so they have equal electrons
What is a disproportionate reaction?
redox reaction where an elements is oxidized and reduced at the same time
What is in an electrochemical cell?
redox reaction takes place
- anode: oxidation; attracts anions
- cathode: reduction; attracts cations
electrons flow from anode to cathode; current flows from cathode to anode
What is the difference between Galvanic and electrolytic cells?
galvanic: spontaneous reactions with positive emf
- concentration cells are when the electrodes are the same material driven by concentration gradient rather than potential difference (Ecell and deltaG is 0)
- anode; - charge
electrolytic: nonspontaneous reactions with negative emf
- anode; + charge
What is a reduction potential?
tendency for a species to gain electrons and be reduced
- the higher, the more the species wants to be reduced
What is the electromotive force?
E0cell: difference in reduction potentials of two half-cells
- galvanic: positive
- electrolytic: negative
E0cell = E0red, cathode - E0red, anode
What is the relationship between Keq and E0cell?
when Keq > 1, Ecell is positive
when Keq < 1, Ecell is negative
What is the delta G equation for electrochemical cell? non standard conditions?
delta G = -nFE0cell
- number of moles of electrons
-F: faraday’s constant
Ecell = E0cell - (0.0592/n) log Q
nFE0cell = RT ln Keq
