Mother Effing Final Flashcards
Reaction Rate is equal to…
[A]/time or P=(nRT)/v because n/v= [A]
Factors that Affect Rate (And how)
Temp- increased temp= more collisions and KE
Concentration- higher [ ] means more collisions per volume
Physical state- as SA increases, so does rate
Which is constant? Rates or K
K
rate of ___1__ = - rate of ___2____
- Product
2. Reactant
First Order Rate Law and Reaction Order
Rate law = K[A]^x where x equals rate order
ln ([Ainitial]/[Afinal])= -Kt
Do First Order Reactions have intermediates?
NOPE
Half life equations for first and second order
First order half life= 0.693/k
Which is longer? T1/2 of 1st or 2nd order reaction?
2nd order
2nd order rate law
(1/[A]final)- (1/[A}initial)=Kt
Reaction Mechanisms
1) Elementary Steps must be physically reasonable (uni- or bi-molecular)
2) Steps must add to give overall eqn
3) Mechanism must correlate with data and rate determining step
Rate determining Step
Slowest step; rate law for this step is the overall rate law
To react, molecules must..?
Collide in space and with proper orientation
Activation Energy
collisions must have a certain minimum energy (Ea) for a reaction to occur
Arrhenius Equation
K=Ae^(-Ea/RT) A=frequency factor Ea= activation Energy R=ideal gas constant (8.314 J/mol K) T= temp in Kelvin
Eqn for finding K from different temps
ln (k1/k2) = (Ea/RT)((T1-T2)/T1T2)
Catalysts
increase reaction rate without being consumed
lowers both forward and reverse Ea by bonding with surface
Homogenous vs heterogenous catalysts
homo: in same state (G-G, L-L)
hetero: in different states (G-S)
At equilibrium, do the [products] and [reactants] change?
No!
Equilibrium
Forward rate = reverse rate
Keq
Equilibrium constant
= [products]/[reactants]
What do the coefficients in a reaction do with Keq equation?
They become exponents
EX: 3A+B–> 2C so Keq= [C]^2/ ([A]^3[B])
K>1
Product Favored
Forward reaction
K
Reactant favored
Reverse reaction
Kp =?????
= Kc (RT)^(change in n)
When to use Q
When you’re not at equilibrium
When Q=K
You’re at Equilibrium
When Q
reactants need consumed
run reverse reaction
When Q>K
products need consumed
run forward reaction
When to use Ice Chart
When you have Keq and initial concentrations…. or basically any time you have the initial concentration of anything.
Le chat’s Principle
if equilibrium is “disturbed”, a net reaction occurs to reduce the effect of the distrubance; new equilibrium concentrations are established
2SO3 reacts to form 2SO2 + O2. If more O2 is added, what will happen?
SO3 will increase while SO2 decreases and O2 increases, then decreases
If you reduce a volume by 1/2, what should you do the the concentrations?
Double them!
Nuclear Reactions are ALWAYS what order?
First
Are mass changes possible in both chemical and nuclear reactions?
No; only nuclear
Atoms can not change identities in (A) chemical or (B) nuclear reactions?
chemical
What is traded in a Chemical reaction? In a Nuclear?
Chemical- electrons
Nuclear- protons and neutrons
Alpha emission
Helium atom
Beta emission
-1 on neutron (bottom number)
Positron
+1 on neutron (bottom number)
gamma ray
positron + electron
change in E= change in m c^2, whats delta m?
delta m = (mass/nucleus)(6.02x10^23 nuclei/mol)
U-238 means…?
there are 283 nucleons in that atom
nucleon
nuetron + proton
Atomic mass
Spontaneous
Reaction that occurs under a certain product-favored set o conditions
Delta G1
Exothermic
product-favored
delta H1; if T>0, K
Entropy
measure of how dispersed the energy is in a system among all the ways energy can be contained
more combinations means higher entropy
State function
Boltzmann equation
S=k log (W) when S=entropy, K=1.38x10^-23 J/K and W= number of microstates
Large volume means more microstates
2nd Law of Thermodynamics
any spontaneous process leads to the increasing energy of the universe
delta S of universe >0
3rd Law of Thermodyamics
Entropy of a perfect crystal at 0 kelvin is 0
(increasing/decreasing) temperature means increasing S
increasing; more molecular motion
Put in increasing order of standard entropy: gas, solid, liquid
solid
delta S(universe) =?
delta S(sys) + delta S(surr) NOT equal to 0
If delta H(sys)>0, then delta S(surr) is..?
if delta H(sys)
> 0
heat is transferred from system to surroundings
delta G(sys) =?
delta H(sys)-T delta S(sys)
If delta H>0 and delta S
> 0(not spontaneous)
If delta H0 then delta G is
If delta H and delta S are >0, then delta G is
High temp: 0 (not Spontaneous)
If delta H and delta S are
High temp:>0 (not spontaneous)
Low temp:
Delta G standard can only be used when the [ ] is
1M
if Q>Keq, then delta G is
> 0
net reverse reaction
if Q
If Q=Keq, then delta G is
=0
Delta G standard =
-RT lnKeq
delta G=
delta G standard+ RT lnQ
delta G (increases/decreases) until equilibrium is met
decreases
Bronsted Acid and base
Acid- proton donor
Base- proton acceptor (needs a lone pair)
Conjugate pairs
chemical species that differ by 1 proton (acid-base pairs)
Autoionization of water
Water can be an acid or a base
2H2O–> H3O+ + OH-
Kw=
[H3O+][OH-]=10^-14
when K
weak
when K»1, the substance is a (strong/weak) electrolyte.
Strong
HA + H2O reacts to form…
H3O+ + A-
large Ka vs small Ka
Large- strong acid
small- weak acid
Ka=
([H30+][A-])/[HA]
the 6 strong acids
HCl, HBr, HI, HNO3, HClO4, H2S04
Strong bases
alkali hydroxides
Ka x Kb=
10^-14 or Kw
strong acids and bases make (strong/weak) conjugate bases and acids
weak
Polyprotic acids
2+ ionizable protons; harder to remove 2nd proton
more energy so delta G increases
Ka2
Across PT Trends on Acid Strength
left to right, more acid strength and less proton affinity
Not based on bond strengths
Down PT Trends on Acid Strength
Going down, acid strength increases and bond strength decreases because smaller atoms mean stronger bonds and waker bonds mean stronger acids
Proton affinity of conjugate bases decreases
Oxoacids
HmEOn Where m and n are small integers and E is the central Atom
Oxoacid strength with PT trends
Going down, acid strength decreases as Ka decreases
Adding O increases acid strength because of electron density in OH bond
Lewis acid vs base
Acid- lone pair acceptor (goes to central atom)
Base- lone pair donor
A Bronsted (can/can’t) be a Lewis, but a Lewis (can/can’t) be a Bronsted.
Can, can’t
Common Ion effect
Basically Le Chat’s; When an ion is added to an equilibrium mixture where it’s already present, the equilibrium shifts away from it
Henderson- Hasselbach Eqn
pH=pKa + log([A-]/[Ha+])
From [A-]=[HA+] to [A-]>[HA+], you must add…
a strong base
From [A-]=[HA+] to [A-]
a strong acid
A buffer acts to convert a strong acid/base to…
a weak acid/base
Buffer Capacity
how much acid/base can be added before “buffering” is lost
Buffer Range
How close you are to pKa of your buffer
Solubility
how much of a solvent dissolves (g/L)
If Q=Ksp, the solution is
saturated
if Q
Unsaturated
If Q>Ksp, the solution is
Super-saturated
If something is soluble, delta S must be
> 0
Redox Reactions
transfer electrons from 1 chemical species to another
Conversion of chemical energy to electrical Energy
Reducing Agent
Is oxidized- positive charge increases
loses electron to substance being reduced
Oxidizing agent
Is reduced- positive charge decrease
gains electron to substance being oxidized
OIL RIG
oxidation is loss, reduction is gain (of electrons)
Oxidation States
sum of oxidation numbers in neutral atom/compound must be zero
Good reducing agents:
are electropositive (left of PT)
electron rich
low oxidation states
Good oxidizing agents:
electronegative (right of PT)
high oxidation states
Half Reaction Rules
- assign oxidation numbers
- write 1/2 reactions
- balance atoms
- balance charge
- cancel electrons and add
Write 1 eqn for whats oxidized and 1 for whats reduced
Standard Reduction Potential
at 1 atm, 1 M
E standard >0 means product favored (delta G
Galvanic Cells
Energy flow from anode (oxidation) to cathode (reduction)
When using Hess with Volts, what should you never do to the voltages???
MULTIPLY BY THE COEFFICIENT
Waterfall analogy
Water=electron in an electrochemical cell
Height of waterfall is proportional to the change in voltage between anode and cathode
Volume of water is proportional to the current (number of electrons/second from a to c)
-nFE(standard)=
delta G standard
delta E(standard)=
(RT/NF) lnK
Nernst Equation
E=E(standard) - (0.59 V/n) log Q
Finally nonstandard!!!!
Q=
[products]/[reactants] = dilute/concentrated
