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DCC: CHE 122 - Gen Chem II > Chapter 13: Chemical Kinetics > Flashcards

Chapter 13: Chemical Kinetics Flashcards

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1
Q

What is chemical kinetics?

A

It is the study of how fast reactions happen and the rate of chance of the reactions.

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2
Q

What do catalytic converters do? What does this require?

A

They accelerate the rates of chemical reactions that turn NO and other pollutants into nonpolluting products. This requires an understanding of chemical kinetics.

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3
Q

What does the rate of a reaction depend on?

A
  1. The physical state of the reactant
  2. The concentration of the reactants
  3. The temperature
  4. A catalyst
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4
Q

How does the physical state of the reaction affect the rate?

A

Kinetic energy increases from solid to gas
Solid: slow b/c not much KE,

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5
Q

How does the concentration affect the rate of the reaction?

A

It depends on the order of the reaction with respect to each reactant.

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6
Q

How is the order of the reaction discovered?

A

Experimentally not mathematically.

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7
Q

What is the relative rate? How is it written?

A

It is how reactants and products change with respect to each other and to time
“How do these reactions relate”
A[X]/At
All parts equal each other. Reactants are negative, products are positive. Coefficients are noted as a denominator.

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8
Q

What are the units of a reaction rate?

A

Molarity/seconds

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9
Q

What is a first order reaction?

A

A rate that depends linearly on only one reactant concentration (ie double concentration double rate)

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10
Q

What is a second order reaction?

A

Reaction proceeds at a rate proportional to the square of the concentration of one reactant (ie if you double the concentration the rate quadruples)

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11
Q

What is a third order reaction?

A

The minimum number of molecules necessary for the reaction to take place is three

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12
Q

What is a zero order reaction?

A

A reaction where the rate does not vary with an increase or a decrease in the concentration of the reactants.

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13
Q

How do you use experimental results to determine the order of the reaction with respect to a certain reactant?

A

Select two experiments in which the concentration of the reactant in question changes while the other reactant remains the same.

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14
Q

What are the units for a zero order reaction?

A

M/s

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15
Q

What are the units for a first order reaction?

A

1/s

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16
Q

What are the units for a second order reaction?

A

1/Ms

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17
Q

What are the units for a third order reaction?

A

1/M^2 s

18
Q

What is the use of integrated rate laws?

A

To determine the reaction rate at anytime using only one experiment. (Calculus is used to create integrated rate law)

19
Q

What is the rate law, integrated rate law, and half-life expression of a zero order reaction?
What is the y vs x and slope of the integrated rate law?

A

Rate = k
[X] = -kt + [X]0
t1/2 = [X]0/2k

[X] vs t m= -k

20
Q

What is the rate law, integrated rate law, and half-life expression of a first order reaction?
What is the y vs x and slope of the integrated rate law?

A

Rate = k[X]
ln[X] = -kt + ln[X]0
t1/2 = 0.693/k

ln[X] vs t m=-k

21
Q

What is the rate law, integrated rate law, and half-life expression of a second order reaction?
What is the y vs x and slope of the integrated rate law?

A

Rate = k[X]^2
1/[X] = kt + 1/[X]0
t1/2 = 1/k[X]0

1/[X] vs t m = k

22
Q

What affects the rate constant k?

A

k is not affected by concentration
k is affected by temperature

23
Q

Why does temperature affect the rate of a reaction?

A

Increased temperature increases Kinetic energy which increases the movement of the molecules and therefore the molecular collisions that break old bonds and build new bonds

24
Q

What is activation energy?

A

Activation energy is the minimum energy of a molecular collision required to break reactants and build products.

25
Q

What does the Arrhenius equation do?

A

It incorporated the factors of temperature and activation energy into the constant k.

26
Q

What is the activation energy with respect to a reaction coordination diagram?

A

Activation energy = highest point on the diagram - the initial energy of the reactants.

27
Q

What is the relationship between temperature and rate?

A

This relationship is not linear. It is exponential: k = Ae ^ -Ea/RT

28
Q

What is A in the Arrhenius equation?

A

A is the collisions frequency factor, that is, the number of successful collisions. Reactants must be in the correct orientation to react.

29
Q

What is R and T in the Arrhenius equation?

A

R is the gas law constant and T is temperature in Kelvin

30
Q

What makes the relationship between temperature and rate linear?

A

ln k = -Ea/R (1/T) + ln A

31
Q

What happens in the reaction when an increase in temperature increases the rate of the reaction?

A

The fraction of collisions with total kinetic energy greater than Ea increases.

32
Q

What is a transition state?

A

It is a species (or state) corresponding to an energy maximum on a reaction energy diagram

33
Q

How do we determine with elementary step is the slowest?

A

Write the rate law of each step and the slowest will match the overall rate law.

34
Q

What are the aspects of a coordinate diagram?

A

Activation energy: highest point - initial energy of the system (reactants)
Activated complex (high energy transition state): highest point: old bonds breaking new bonds form

35
Q

What is the point of reaction mechanisms?

A

Reaction mechanisms tell exactly what is happening in the reaction, that is, what molecules are colliding in what orientation. They can be used to determine a rate of reaction and the rate law, but this must match experimentally determined

36
Q

What is the relationship between the activation energy and the constant.

A

Low activation energy means a large constant meaning a fast reaction.

37
Q

Can the Arrhenius equation be used to determine a temperature?

A

Yes, if you have a final and initial constant and an initial temperature you can determine a final temperature

38
Q

What is a reaction mechanism?

A

It is a set of steps at a molecular level (it is broken into elementary steps). Could be bimolecular (two molecules as reactants) or unimolecular (one molecule as reactant)

39
Q

What are intermediate molecules?

A

Molecules produced in one step and used up in another

40
Q

What is the rate-determining step?

A

It is the slowest step that determines how fast a reaction will occur. This is important for organic chemistry

DCC: CHE 122 - Gen Chem II (8 decks)

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