Card Set Information
General Chemistry MCAT
charge of 1 e
1.6 x 10
isotopes (# of protons and neutrons)
same # of protons
different # of neutrons
metals = oxidizing or reducing agents?
tend to lose e
elements of same family or period are most similar
quantum mechanics: what does n and l represent?
n = energy level
l = shape of orbital
"hypo" = first
"per" = last
quantum mechanics: increase in n does what?
increases size and energy of e
quantum mechanics: e
in the same orbital share what common characters?
same 1st 3 numbers, different 4th:
same shell (n), subshell (l), orbital
different spin (+1/2) or (-1/2)
what is electron affinity?
amt. of energy released when an e
what is electronegativity?
ability of atom to draw in e
from a bond
periodic trend: electron affinity
increases right to left, bottom to top
diagonally left and right
periodic trend: electronegativity
increases left to right, bottom to top
periodic trend: acidity
increases left to right, top to bottom
(right diagonal down)
noble gases have exclusively what intermolecular bonds?
van der Waals
Are larger or smaller atoms more polarizable?
larger atoms - further away
van der waals interactions are:
temporary dipole-dipole moment
relative strengths of intermolecular forces
van der Waals
STP (temperature and pressure)
1 atm (760 torr)
At STP, how much volume does 1 mole of a gas occupy?
describe ideal gases
1. zero volume
2. no forces other than repulsive in collision
3. elastic collisions
4. avg. KE proportional to temperature
are intermolecular forces taken into account in ideal gases?
PV = nRT (R value)
ideal gas: KE and temperature
avg. KE is proportional to temperature
, ideal pressure/volume or real pressure/volume
what deviates from "ideal"
when molecules are close together
ideal temperature and pressure
high temperature and low pressure
(so molecules are far apart)
what are more ideal: monoatomic gases or diatomic gases (H
noble gases at STP are what kind of gases?
pinhole - spreading from high to low pressure
which gases will find pinhole easier?
gases with higher rms velocity
spreading into another gas or empty space
Partial pressure equation
avg. KE of gases in a gas mixture
decrease KE of a gas will do what to PE?
molecules bind together more
will KE be the same throughout a gas mixture?
no, only their average kinetic energies
why will KE vary from molecule to molecule?
they have different molecular weights
equation of KE of gases in a mixture
= sq. root (mass
effusion and diffusion rates
inversely proportional to sq. root of their mass
which gas will diffuse/effuse faster O
because it's lighter
as gas with strong or weak IM forces will exert more pressure on a container?
weak intermolecular forces
Kinetics: rate of a reaction increases when:
[reactants] and temperature
half life of 1st order reaction
Kinetics v. Thermodynamics
kinetics = rate (getting to state)
thermodynamics = G, S, H (prop. of this state)
heat transfer (3 forms)
how does conduction transfer heat?
conducts heat from hot to cold reservoir
(higher energy to lower energy)
conducting capability of slab and length
doesn't matter -
same regardless of length
what about temperature difference between slabs?
increase distance = increase temperature difference
Is rate of flow across slabs constant or varies?
convection transfers heat how?
radiation transfers heat how?
What is work?
energy transfer that is not heat
Work (pressure and volume)
W = -P x change in V
work at constant volume
no work is done
Total energy of a system:
E = q + W
total energy at constant volume
since no work, E = q
work at constant temperature
W = -q
total energy at constant temperature
E = 0 because E is proportional to T
energy flow into and out of the system
out of (+)
How is enthalpy calculated? What is the formula?
H = change U + P changeV
H = E
What is enthalpy of formation?
change in enthalpy when a compound is formed from raw elements
enthalpy at constant P
H = change U + P change in V
H = W + U
element in standard state at 25
H = 0 J/mol
endothermic v. exothermic and delta H
endothermic (+) - absorbs heat
exothermic (-) - releases heat
energy of activation greater for endothermic or exothermic?
what elements are H
standard state elements - O
entropy of universe must always be positive or negative?
equation for entropy
delta S = Q/T
entropy change between hot and cold reservoir: positive or negative?
hot = negative (energy is leaving system)
cold = positive (energy is entering system)
entropy for any isolated system that is irreversible must be....
entropy of universe must always be > 0
increase # of moles of gas does what to entropy?
increase in temperature = what to entropy
increase in entropy
reaction at equilibrium will maximize....
universal entropy (not entropy of system)
spontaneous = positive or negative entropy?
positive (more disorder)
exergonic and endergonic
exergonic = spontaneous
endergonic = non-spontaneous
delta G and spontaneity
(-) = spontaneous
(+) = non-spontaneous
What is Gibbs Free Energy?
energy available to do work
equation for Gibbs Free Energy
delta G = delta H - Tdelta S
more disordered (greater S) does what to Free energy
negative free energy = spontaneous
because universe tends towards greater disorderedness
G and K
delta G = -RT lnK
G = 0 then K
K = 1
what does K = 1 indicate?
products and reactants are equal
G < 0 and G > 0
(-) G = K > 1
(+) G = K < 1
K < 1
reactants are favored
K > 1
products are favored
1L of water = how many kilograms?
1L = 1kg of water
1L water = how many moles?
solution mixture v. separated pure substances (G and S)
solution = more disordered = inc. entropy = decrease G
pure solids and liquids
leave them out
what is solubility? (measured)
# moles/ L
how does pressure affect solubility of gases?
how does temperature affect solubility of salts
increases solubility of salts
how does temperature affects solubility of gases?
What is heat capacity?
measure of energy change needed to change temperature of substance
no work (W=P change in V)
work at constant pressure... why?
yes because substance can expand, so substance absorbs energy
heat capacity formula
q = C x change in T
heat capacity per unit mass
q = mc change T
are heat capacities different according to phase?
specific heat of water
1 calorie = 4 joules
when a substance releases heat, temperature or pressure change?
yes, but either temperature or heat, not both
increasing non-volatile solute does what to vapor pressure?
decreases vapor pressure
increasing non-volatile solute does what to boiling point
decreases boiling point
osmotic pressure formula
Molarity x 0.8 x T x i
Free Energy Equation
delta G = H - TS
entropy at low temperatures
not much influence
ions dissolved in solution are called
able to conduct electricity
is water a conductor of electricity?
yes, polar conductor
unless it contains electrolytes
0.2 moles of NaCl will dissociate how?
will produce 0.2 moles of Na+ 0.2 mol of Cl-
vapor pressure: what holds down the molecules?
how can molecules break intermolecular forces?
have enough KE (for a gas)
if molecules are rising above to space, how can they be in equilibrium
force some mol. to crash back down
eq. = same # leaving and returning
(+) and (-)
negative = stronger bonds are formed
positive = weaker bonds are formed
stronger bonds and weaker bonds affecting vapor pressure
strong = lowers vapor pressure
weaker = raises vapor pressure
concentration of dissolved salt reaches maximum
vapor pressure and boiling point
increased vapor pressure = decrease in boiling point
Heat of transition (phase change)
magnitude is related to.....
strength of intermolecular forces
delta H fusion
delta H vaporization
are melting and boiling endothermic or exothermic
heat is being added, temperature increases
solid to gas
gas to solid
solid to liquid (melting
liquid to solid (freezing)
exists in equilibrium as a solid, liquid, gas
temp. where a substance cannot be liquefied
pressure required for liquidification at critical temp.
critical temperature and critical temperature
1 atm in phase diagram
definition of Lewis acid/base:
definition of Bronsted/Lowry acid and base
acts as either acid or base
example of amphoteric substance
acids that can donate more than one proton
all strong bases
strong acids and bases in water....
F - Cl - Br - I
F - Cl - Br - I
decreasing bond strengh
F - Cl - Br - I
conjugate base: more oxygens...
why do more oxygens make stronger acids?
O draws e
to one side, increasing polarity
periodic table: acidic and basic
left = basic
right = acidic
periodic trend for acidity
increases right and down
hydrides are what kind of compounds?
binary compounds = only 2 elements
pH = -log[H
pOH = -log[OH
pH + pOH add to...
pH + pOH = 14
] and [OH
] of strong acids/bases in solution
strong acids and bases dissociate completely in solution -
] and [OH
] are the same as original conentrations
weak acids and bases concentrations [H
] and [OH
What is the pH of 1M of HCl?
pH = 0
] = 1 and 10
What is value of K
] / [HA]
value means what
small pKa means what value of Ka
small pKa = large K
= strong acid
acids and bases combine
to from water + salt
how do you determine pH of salt solution?
look at conjugates of ion
Cl dissociation neutralization
conjugates = NaOH and HCl
both strong, so Na
buffering region of titration curve
all acid has been converted to base
equivalence point of titration of strong acid by strong base
equivalence point: stronger acid than base
EP < 7
equivalence point: stronger base than acid
pH > 7
half equivalence point
[acid] = [base]
have more than 1 EP and more than 1 1/2 EP
polyprotic titrations: when does second proton begin to dissociate?
once the 1st proton has
no change in pH upon addition of acid or base
At what point in the titration curve is the solution buffered?
1/2 equivalence point
because [HA] = [A
pH = pK
pH at half-equivalence point
[HA] = [A
] so pH = pK
how do you make buffer solutions?
mix equal amounts of acid with conjugate base
basic = red to blue
acidic = blue to red
endpoint in titration
when indicator changes color
loss of e
gain of e
the lion says.....
the lion says
oxidation state of F, H, and O
F = -1
H = +1
O = -2
is water and oxidizing or reducing agent?
poor oxidizing and reducing agent
balancing redox rxns:
balance other elements
O - balance O
- balance H
- balance charge
energy transfer in galvanic cell
chemical energy to electrical energy
T - E - I - E' - T
T = terminals
E = electrodes
I = ionic conductor
what is the salt brigade?
ionic conducting phase
what does ionic conductor (salt bridge) do?
carries current (in the form of ions)
electric potential difference from T to T
anode and cathode (charge)
anode = (-)
cathode = (+)
mnemic for redox reactions
RED CAT - AN OX
reduction cathode - anode oxidation
when is it spontaneous?
positive cell potential (E)
what is cell potential? (emf)
potential difference between terminals when they're connected
what does connecting terminals do to potential difference
reduces potential difference
Anode l Anoic solution ll Cathodic solution l Cathode
free energy and chemical energy equation
delta F = -nFE
what does n represent [G = -nFE]
number of moles
E = E
What is the cell potential at equilibrium?
E = 0
because no rxn is favored
identical electrodes whose half cells have different ion concentation
current flows toward
toward greater entropy
require force by outside power source
Cell potential for H
E = 0
Heisenburg uncertainty principle:
position and momentum
fall from higher energy state to lower energy state
photon is released
(energy is released in form of a photon)
what is the energy of this photon?
E = hf
what happens when a photon is absorbed?
is bumped to a higher energy state