Final Test (4, 12, beginning of 7) Flashcards
What is a redox rxn
transfer of e-
Oxidation State Rules
EMFOH
E: elements: 0
Monoatomic ion: charge of ion
Fluorine: -1
Oxygen: -2 except for O22- (it is -1 in this)
Hydrogen: +1
Steps for oxidation reduction reactions in acidic solution
HALF REDUCTION METHOD
1. Write separate equations
2. For each reaction
- balance all elements except H and O
-Balance O using H20
-Balance H using H ions
-Balance charges using e-
3. If necessary, multiply one or both rxns by an integer to equalize e-
4. add half rxns together, cancel identical species
5. check that elements and charges are balanced
speed of light?
2.9979 *(10^8) m/s
equation for waves?
wavelength*frequency = speed of light
steps for half-rxn in basic solutions?
- Use half-reaction method like acidic solutions
- add OH- ions to counter H+ ions
- Form H2O on side3 containing H+ and OH- and cross out duplicates on other side
- check if elements and charges are balanced
How are collisions and reaction rate related?
more collisions is a higher reaction rate
How does concentration affect rxn rate?
speeds up rxn because it leads to more collisions
how does temp affect rxn rate?
more temp leads to increased collisions because kinetic energy and speed
What is activation energy?
min energy required to start a rxn
What is a catalyst?
speeds up rxn without being consumed and lowers EA
What is a reaction rate?
a change in concentration of a reactant or product per unit of time.
what is average rate?
exactly what it sounds like
what is instantaneous rate?
slope at a point of delta concentration over delta time
how do equation coefficients relate to rxn rate coefficients
aA + bB -> cC + bB
(-1/a)(Δ A/Δ t) =
(-1/b)(Δ B/Δ t) =
(1/c)(Δ C/Δ t) =
(1/d)(Δ D/Δ t) =
what is rate law?
rate = k[A]m[B]n
k is a constant
m and n are the orders of the reactants
what are rxn orders?
0: rate independent of concentration
first order: rate is directly proportional to concentration of reactant
second order: rate is proportional to square of conc.
overall reaction order: sum of individual orders
general formula for units of K
M1-n*t-1
n is overall rxn order
how to tell by graphs what order a rxn is?
0 order: ∆[A]/∆t is linear
1st order: ln(∆[A])/∆t is linear
2nd order: (1/∆[A])/∆t is linear
Integrated rate laws:
zero order: [A] = -kt + [A]0
first order: ln[A] = -kt + ln[A]0
second order: 1/[A] = kt + 1/[A]0
half life formulas
half life =
0 order: [A]0/2k
1st order: 0.693/k
2nd order: 1/(k*[A]0)
Arrhenius Equation w/ temp and activation energy
k= Ae-Ea/RT
-Ea is activation energt
- A is freq factor
- R is gas constant (8.314)(J/K*mol)
- exponential factor is a # between 0 and 1 that reps the fraction of molecules that have enough energy to make it over activation barrier
Main takeaway: temperature affects rxn rate!!!
What are rxn mechanisms
most chemical reactions occur through several steps, and a mechanism is a series of individual chemical steps by which an overall rxn occurs. Each step is an elementary step, which cannot be broken down further and they have to add to the overall reaction.
what is a reaction intermediate?
something that is formed by a mechanism and is consumed afterwards. Not in reactants or products.
rate laws for elementary steps and rate determining step?
in a series of elementary steps, there is a slow step which usually determines the overall rate of the rxn. If the first step is the slow step, the rate law only contains the reactants involved in the overall rxn. If the first step is fast and another is slow, rate law may contain intermediates. To overcome this, you have to solve for the concentration of the intermediate by assuming that an equilibrium is established in the first step.
What is a homogenous catalyst? heterogenous?
Homo: all reactants and products are in same state of matter
hetero: all reactants and products are in more than 1 state
- for hetero, this usually entails fluids like gases adsorbing onto a solid surface.
what does adsorbing mean?
the process by which a solid holds a liquid or gas onto its surface as a thin film.
what are the steps for a heterogenous catalyst reaction?
- adsorption and activation of reactants
- migration of reactants on solid
- reaction of adsorbed substances
- escape (desorption) of products
What is an acid/base catalyst?
acids and bases that serve as catalysts. Look at examples.
what is Planck’s constant?
he found that energy can only be gained or lost in whole numbers of hv! h: plancks constant (in cheat sheet). v= frequency
What are packets of energy that occur in discrete unit size hv?
quantum or quanta plural. Quanta have magnitudes that depend on substance
Who proposed that EMR is quantized? how can EMR be viewed?
Einstein. Streams of particles called photons
what is the photoelectric effect?
metals emit e- when photons strike them.
Properties of photoelectric effect?
each metal has a min frequency of light for emission to occur, and each photon has an energy proportional to that light frequency. For light w frequency lower than the threshold, no e- will be emitted regardless of intensity of light. For light w/ freq greater than threshold, e- emitted increases with intensity. For light w/ frequency greater than threshold, KE of emitted e- increases linearly w/ frequency of light.
energy of photon equation?
E = hv = hc/λ
what does e=mc2 signify?
energy has mass, calculated using energy associated w quantity, m = E/c2
with this, you can calculate mass of a photon: m = E/c2, m = (hc/λ)/c2, m = h/λc
