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chem110 > Block 3: Kinetics > Flashcards

Block 3: Kinetics Flashcards

1
Q

What is the rate of a chemical reaction?

A

The change in concentration per unit time (usually mol L-1 s-1)

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2
Q

What is the rate of a reaction equation?

A

Rate = - 1/a x (delta [A]/ delta t)

A= reactant a

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3
Q

What factors affect the rate of reaction?

A
  • the nature of the reaction (eg metallic sodium reacts with O2 to form oxide fast, iron= slowly, gold= not at all)
  • concentration of reactants
  • the temperature
  • physical state of reactants (eg powder = larger surface area= fast)
  • presence of catalysts
  • action of light
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4
Q

How is the instantaneous rate of many reactors related to the concentration of reactants?

A

By a rate law

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5
Q

What is a first order reaction and what does it mean?

A

The rate is directly proportional to the concentration of the reactant; if the concentration is doubled, the rate doubles

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6
Q

What is a second order reaction and what does it mean?

A

The rate is proportional to the square of the concentration; if the concentration of the reactant is doubled, the rate increases by a factor of 4

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7
Q

Equation for first order reaction?

A

Rate {proportional to} [A]

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8
Q

Equation for a second order reaction?

A

Rate {proportional to} [A]^2

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9
Q

What is a zero order reaction?

A

Where rate is independent of concentration

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10
Q

What is a third order reaction?

A

Where rate is proportional to the cube of a concentration

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11
Q

What is an instantaneous rate?

A

Rate at a particular time during the course of reaction and is the same as the slope

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12
Q

What happens to the rate if you have more than one reactant concentration?

A

It’s proportional to both;

Rate {proportional to} [A] x [B]

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13
Q

What is the proportionality constant? What, therefore, is the reaction?

A

The rate constant, or “k”

Therefore; rate = k [A] x [B]

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14
Q

What’s the initial rate?

A

The change in concentration

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15
Q

How do we work out the units?

A

By balancing the rate units/the concentration^2

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16
Q

What are the units of a first order rare constant?

A

S-1

17
Q

What’s the concentration of zero order rate reaction?

A

Mol L-1 s-1

18
Q

What happens as order increases?

A

Rates become slower

19
Q

How would you rearrange

Rate= k[A][B]^2 to find the k value?

A

K = rate / [A][B]^2

20
Q

What is an integrated first order rate law equation?

A

[R] = [R]oe^-kt

R= conc of reactant after time 
Ro= conc of reactant at start 
t= time in seconds
21
Q

What’s the integrated form of a second order reaction? (Reactants to products)

A

1/[R] = 1/[R]o + kt

22
Q

Does the first order plot of integrated law rate make a straight line?

A

Yes

23
Q

Does the second order graph of integrated law make a straight line?

A

No, it’s curved

24
Q

What is the half-life of a reactant?

A

The time it takes for a reaction to fall to half of its initial value, denoted by symbol t 1/2

25
Q

What does the half life depend on?

A

The order of the reaction

26
Q

First order half life law?

A

[R]/[R] = 1/2= e ^(kt 1/2)

Which goes to

T1/2 = ln2/k

27
Q

What’s the initial rate?

A

The change in concentration

28
Q

How do we work out the units?

A

By balancing the rate units/the concentration^2

29
Q

What are the units of a first order rare constant?

A

S-1

30
Q

What’s the concentration of zero order rate reaction?

A

Mol L-1 s-1

31
Q

What happens as order increases?

A

Rates become slower

32
Q

How would you rearrange

Rate= k[A][B]^2 to find the k value?

A

K = rate / [A][B]^2

33
Q

What is an integrated first order rate law equation?

A

[R] = [R]oe^-kt

R= conc of reactant after time 
Ro= conc of reactant at start 
t= time in seconds
34
Q

What’s the integrated form of a second order reaction? (Reactants to products)

A

1/[R] = 1/[R]o + kt

35
Q

Does the first order plot of integrated law rate make a straight line?

A

Yes

36
Q

Does the second order graph of integrated law make a straight line?

A

No, it’s curved

37
Q

What is the half-life of a reactant?

A

The time it takes for a reaction to fall to half of its initial value, denoted by symbol t 1/2

38
Q

What does the half life depend on?

A

The order of the reaction

39
Q

First order half life law?

A

[R]/[R] = 1/2= e ^(kt 1/2)

Which goes to

T1/2 = ln2/k

chem110 (6 decks)

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