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Chem 106 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

what is the driving force behind a spontaneous reaction?

A

motional freedom of particles increasing

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2
Q

during a spontaneous chemical reaction, it is found that the change in Ssys is less than 0. what does this mean?

A

the change in Ssurr is greater than 0 and its magnitude is greater than the change in Ssys

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3
Q

when is a process always spontaneous?

A

change in H<0 and change in S>0

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4
Q

second law of thermodynamics

A

the entropy of a universe increases in any spontaneous reaction

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5
Q

third law of thermodynamics

A

entropy of a perfect crystal at absolute zero is 0 while W=1
provides a baseline/refrence for entropy

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6
Q

microstates

A

unique distribution of particles among energy levels

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7
Q

how does entropy affect spontaneity?

A

S<0 less spontaneous

more spread out means its more spontaneous

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8
Q

what factors affect reaction rates?

A
  • physical state of reactant
  • concentration of reactants
  • temperature
  • presence of a catalyst
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9
Q

enthalpy

A

change in heat

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10
Q

three types of motion

A

translational, vibrational, rotational

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11
Q

how does temperature influence spontaneity?

A

higher temperature means increase in collisions, therefore higher spontaneity

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12
Q

integrated rate law

A

change in concentration of a reactant with time

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13
Q

units for 0th order

A

M/s

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14
Q

units for 1st order

A

1/s

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15
Q

units 2nd order

A

1/Ms

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16
Q

activation energy

A

minimum energy needed to break bonds in reactants and form bonds in the products

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17
Q

transition state/activation complex

A

high energy transition state

peak

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18
Q

reaction mechanisms

A

set of steps that describe how a reaction occurs at the molecular level

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19
Q

rate-determining step

A

slowest step in the reaction

20
Q

homogeneous catalyst

A

catalyst in the same phase as the reactants

21
Q

heterogeneous catalyst

A

catalyst in a different phase from the reactants

22
Q

catalysts

A

not consumed, speeds up reaction, lowers activation energy

23
Q

what must happen for a reaction to occur?

A
  1. molecules must collide
  2. must exceed the threshold energy
  3. must collide with proper orientation
24
Q

how does a lower energy affect a spontaneous reaction?

A

makes it more stable

25
Q

what is energy distribution affected by?

A

molecular motion and volume

26
Q

energy state/level

A

allowed value of energy

27
Q

w

A

number of microstates

28
Q

is motion a type of kinetic energy?

A

yea

29
Q

what increases with temperature?

A

motion

30
Q

how do exothermic reactions affect their surroundings?

A

have the possibility to increase the entropy of their surroundings

31
Q

what is the energy change of a reversible process?

A

no net flow of energy between the system and the surroundings

32
Q

what does the entropy change experienced by the surroundings of a chemical thermodynamic system depend on?

A

whether the process is exothermic or endothermic

33
Q

what remains constant with Gibbs free energy?

A

temp and pressure

34
Q

if something is spontaneous what is the change in G of the system equal to?

A

less than 0

35
Q

what does a reaction rate depend on?

A

concentration

36
Q

what happens to the reaction rate as the concentration decreases?

A

the reaction rate decreases

37
Q

how are exponents in a rate law determined?

A

experimentation only

38
Q

does the rate constant depend on the concentration of the reactants?

A

nah

39
Q

what controls the reaction rate in a pseudo-first-order reaction?

A

concentration of the limiting reactant

40
Q

pseudo-first-order

A

all reactants but one are present at such high concentrations that they don’t decrease significantly during the reaction

41
Q

zero order

A

rate of reaction is independent of concentration

42
Q

3rd order units

A

1/M2s

43
Q

rate law for 0 order

A

rate=k

44
Q

which order has 1/something

A

second order

45
Q

how does a larger value of W affect entropy?

A

more entropy!!

Chem 106 (13 decks)

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