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Chem > Chem 330 final > Flashcards

Chem 330 final Flashcards

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1
Q

what is the differential rate law (often called just the rate law)

A

expresses how the rate depends on concentration

rate/concentration

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2
Q

what is the integrated rate law

A

expresses how the concentration depends on time

concentration/time

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3
Q

if a reaction is first order with respect to a reactant, how does the concentration of the reactant affect the reaction rate

A

doubling the concentration of the reactant doubles the reaction rate

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4
Q

what is the method of initial rates

A

several experiments are carried out using different initial concentrations and the initial rate is determined for each run. the results are then compared to see how the initial rate depends on the initial concentrations

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5
Q

what is the half life of a reaction

A

the time required for a reactant to reach half of its original concentration

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6
Q

for a first order reaction, does half life depend on initial concentration

A

no, it depends only on k

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7
Q

for a second order reaction, does half life depend on initial concentration

A

yes, it depends both on initial concentration and on k

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8
Q

for a second order rxn, how is each half life related to the next one

A

each successive half life is double the preceding one

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9
Q

what is a pseudo first order rate law

A

a rate law obtained by simplifying a more complicated one; i.e. when the concentration of 2 reactants is so large compared to a third that the 3 large can be considered constant

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10
Q

what is an elementary step

A

a reaction whose rate law can be written from its molecularity

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11
Q

what is molecularity

A

the number of species that must collide to produce the reaction indicated by that step

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12
Q

what is a unimolecular step

A

a rxn involving one molecule

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13
Q

what is a bimolecular rxn

A

rxns involivng the the collision of two species

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14
Q

what is a termolecular rxn

A

rxns involivng the the collision of 3 species

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15
Q

what is a reaction mechanism

A

a series of elementary steps that must satisfy two requirements:

(1) the sum of the elementary steps must give the overall balanced equation
(2) the mechanism must agree with the experimentally determined rate law

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16
Q

what is the rate-determining step in a reaction

A

the slowest step b/c a reaction is only as fast as its slowest step so this step determines the rate

17
Q

how does temperature affect the speed of a reaction

A

chemical reactions speed up when temperature is increased

18
Q

what is activation energy

A

a threshold energy that must be overcome to produce a chemical reaction

19
Q

why do only a small fraction of collisions produce a reaction

A

b/c the collisions need to have enough energy to overcome the activation energy and because the collisions need to have the correct orientations

20
Q

how is activation energy related to the speed of a reaction at a given temperature

A

the higher the activation energy, the slower the reaction

21
Q

what is the activated complex/transition state

A

the arrangement of atoms found at the top of the potential energy ‘hill’ or barrier

22
Q

how do catalysts make reactions go faster

A

they provide a new pathway for the reaction to occur, and this pathway has a lower activation energy; this allows a much larger fraction of the collisions to be effective at a given temperature

23
Q

do catalysts affect the energy difference between products and reactants?

A

no

24
Q

what is wavelength

A

the disance between two consecutive peaks or troughs in a wave

25
Q

what is frequency

A

the number of waves per second that pass a given point in space

26
Q

how are wavelength and prequency related

A

inversely proportional

27
Q

in what quantities is energy gained/lost

A

only in whole number multiples; energy is quantized and can be transferred only in discrete units of size hv

28
Q

what are the small ‘packets’ of energy called

A

quantum; a system can transfer energy only in whole quanta

29
Q

what are photons

A

particles representing a quantum of light or other electromagnetic radiation

30
Q

what is the photoelectric effect

A

refers to the phenomenon in which electrons are emitted from the surface of a metal when light strikes it

31
Q

what 4 observations characterize the photoelectric effect

A
  1. no electrons are emitted by a given metal below a specific threshold frequency
  2. for a light w/ frequency lower than the threshold frequency, no electrons are emitted regardless of the intensity of the light
  3. for light w frequency greater than the threshold frequency, the number of electrons emitted increases with the intensity of the light
  4. for a light with frequency greater than the threshold frequency, the kinetic energy of the emitted electrons increases linearly with the frequency of the light
32
Q

what does the threshold frequency represent for electromagnetic radiation

A

the minimum energy required to remove the electron from the metal’s surface

33
Q

for light with frequency greater than the threshold frequency, where does the excess energy go

A

it is given to the electron as kinetic energy

34
Q

when a system loses energy, what happens to its mass

A

it also loses mass

35
Q

what is the dual nature of light

A

electromagnetic radiation exhibits wave properties and certain characteristics of particulate matter

36
Q

what is the significance of the line spectrum of hydrogen

A

only certain energies are allowed for the electron in the hydrogen atom; the energy of the electron in the hydrogen atom is quantized

37
Q

what is the heisenberg uncertainty principle

A

there is a fundamental limitation to just how precisely we can know both the position and the momentum of a particle at a given time; the more precisely we know position, the less precisely we know momentum, and vice versa

38
Q

what is the pauli exclusion principle

A

in a given atom no two electrons can have the same set of 4 quantum numbers; each orbital can only hold two electrons and they must have opposite spins

39
Q

what is hund’s rule

A

the lowest-energy configuration for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli principle in a particular set of degenerate orbitals

Chem (20 decks)

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