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CHEM114 > lecture 7 thermo > Flashcards

lecture 7 thermo Flashcards

1
Q

Thermodynamics tells us what?

A

Whether a reaction can occur spontaneously or not

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2
Q

True or False? Thermodynamics tells us how fast spontaneous reactions will occur

A

False

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3
Q

Chemical kinetics is the study of what?

A

Reaction rates

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4
Q

Why is having info about rates of reactions important?

A

For reasons such as knowing the effects of pollutants on the environment, the ripening rates of fruits, and the degrations rates of food and pharmaceuticals ect

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5
Q

Measuring reaction rates can give information about what?

A

Reaction mechanisms aka the sequence of steps that give the overall reaction

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6
Q

Knowledge and understanding of reaction mechanisms is important why?

A

For the understanding of treatment of disease, industrial processes, and reactions in the atmosphere (climate change) e.c.t

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7
Q

True or False? A reaction involving more than two species is highly unlikely to occur in a single step

A

True

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8
Q

True or False? Reactions between two species will always occur in a single step

A

False, they may not always

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9
Q

Reaction mechanisms are what?

A

The sequence of elementary steps by which the overall reaction occurs.

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10
Q

What is an elementary step?

A

A single step

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11
Q

What is the slow step of a multi-step reaction?

A

The rate determining step which controls the overall reaction rate.

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12
Q

Rates of a chemical reaction are always what?

A

Positive

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13
Q

Rate can be measured by what?

A
  1. Rate of appearance of a product = delta conc of product / delta time
  2. Rate of appearance of reactant = delta conc of reactant / delta time
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14
Q

True or False? The rates of appearance of products and dissapearance of reactants are related.

A

True

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15
Q

The rates of most reactions are found to depend on what?

A

The concentration of the reactants

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16
Q

The higher the conc of reactants in a reaction what?

A

The higher the frequency of successful collisions therefore the higher the reaction rate.

17
Q

What do rate equations (rate laws) give?

A

The relationship between the conc of reactants and the rate of the reaction

18
Q

What does k stand for?

A

Rate constant (or rate coefficient)

19
Q

What is the generic reaction for rate equations?

A

aA + bB > xX + yY
Rate = k[A]m[B]n
M does not necessarily = A and n does not necessarily = B

20
Q

k depends on what?

A

T so is calculated for a particular T

21
Q

The larger k is, is the reaction faster or slower?

A

The reaction is faster

22
Q

The powers m and n in the rate equation give what?

A

The order with respect to that reactant

23
Q

What does 0 order mean?

A

This means a reactant doesn’t appear in the rate law

24
Q

How do you calculate the total reaction order?

A

m + n

25
Q

Any number to the power of 0 = what?

A

1

26
Q

For k (rate constant) what is the order for A and B and what is the overall reaction order.

A

Order in A = 0
Order in B = 0
Overall order = 0

27
Q

For k[A] (rate constant) what is the order for A and B and what is the overall reaction order.

A

Order in A = 1
Order in B = 0
Overall order = 1

28
Q

For k[A][B] (rate constant) what is the order for A and B and what is the overall reaction order.

A

Order in A = 1
Order in B = 1
Overall order = 2

29
Q

For k[A]2[B] (rate constant) what is the order for A and B and what is the overall reaction order.

A

Order in A = 2
Order in B = 1
Overall order = 3

30
Q

What does the reaction order determine?

A

The units of the rate constant (k)

31
Q

What are the units for a second order reaction?

A

L mol-1 s-1

32
Q

What are the units for a zero order reaction?

A

mol L-1 s-1

33
Q

What are the units for a first order reaction?

A

s-1

34
Q

What are the units for a third order reaction?

A

L2 mol 2- s-1

CHEM114 (16 decks)

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