Kinetics 2

Question 1

What does the rate equation describe?

Answer 1

How the rate of reaction at a particular temperature depends on the concentration of the species involved

Question 2

What is the rate of equation?

Answer 2

rate = k [A]* [B]*

Question 3

Define autocatalysis

Answer 3

When a catalyst appears in the rate equation

Question 4

What is an order?

Answer 4

The degree of effect to which change in a reactant has on rate

Question 5

What does order zero mean?

Answer 5

A change in the concentration of the reactant has no effect on the rate

Question 6

What does order one mean?

Answer 6

A change in the concentration of the reactant is directly proportional to change in the rate

Question 7

What does order two mean?

Answer 7

A change in the concentration of the reactant is proportional to change in rate squared

Question 8

How do the orders appear in the rate equation?

Answer 8

Order zero: does not appear
Order one: [A]
Order two: [B]2

Question 9

What is the overall order of a reaction?

Answer 9

Sum of all the orders of the species involved in a reaction

Question 10

How do you determine k from the rate equation?

Answer 10

1. Determine the order of the reactants
2. construct the rate equation
3. rearrange for k
   rate/[a][B]
4. determine units for k
5. calculate value for k

Question 11

Define rate of reaction

Answer 11

Change in concentration per unit time

Question 12

What is the rate determining step?

Answer 12

The slowest step in a mechanism for a reaction

Question 13

Are species involved only after the rate determining step in the rate equation?

Answer 13

No

Question 14

What are the two rules involving the rate equation and the rate determining step?

Answer 14

-only species involved up and to including the RDS appear in the rate equation

• must be enough of each species to fulfil the rate equation
• –> ie: if rate=k[W]2[X] = all reactants up to RDS must have 2x W per X

Question 15

What is the arrhenius equation?

word

Answer 15

The link between the rate constant, activation energy and temperature

Question 16

What is the arrhenius equation?

Actual equation

Answer 16

k = Ae ^-Ea/RT

Question 17

Arrhenius equation: what is the exponential and what does it represent

Answer 17

e ^-Ea/RT

The fraction of collisions with enough energy to react

Question 18

What is the logarithmic form of the arrhenius equation?

Answer 18

ln(K) = -Ea/RT + ln(A)

Question 19

Why is the logarithmic form of the arrheius equation used?

Answer 19

It is easier to use the arrhenius equation when you take (natural) logs of both sides to the base e

Question 20

What does the logarithmic form of the arrhenius equation equate to?
hint: graphs

Answer 20

Equates to the equation of a straight line graph
ln(K) = -Ea/R x 1/t + ln(A)
Y = m x + c

Question 21

What is the effect of increasing the activation energy on the arrhenius equation and therefore rate of reaction?

Answer 21

1. The fraction is larger and more negative
2. t/4 the value of the exponential is smaller
3. t/4 k is smaller
4. t/4 decreased rate of reaction

Question 22

What is the effect of increasing the temperature on the arrhenius equation and therefore rate of reaction?

Answer 22

1. The fraction is smaller and less negative
2. t/4 the value of the exponential is bigger
3. t/4 k is bigger
4. t/4 increased rate of reaction

Question 23

Arrhenius equation with Ea as the subject

Answer 23

Ea = (ln(A)-ln(K)) (R x T)

Question 24

Arrhenius equation with T as the subject

Answer 24

T = Ea/ R x (lnA-lnK)

Question 25

Arrhenius equation with A as the subject

Answer 25

A = K/ e^ -(Ea/RT)

Question 26

What is the effect of concentration of a solution on. rate?

Answer 26

The higher the conc, the faster the reaction (unless zero order)

Question 27

Why does rate increase with conc of reactants?

Answer 27

The particles are closer together and so there are more frequent collisions

Question 28

What is the effect of surface area of a solid on rate?

Answer 28

The greater surface area, the faster the reaction

Question 29

Why does rate increase with surface area?

Answer 29

There are more particles exposed at the surface that can be collided with, and so there are more frequent successful collisions

Question 30

What is the effect of pressure of gases (reactants) on rate?

Answer 30

The higher the pressure, the faster the reaction (unless zero order)

Question 31

Why does rate increase with pressure of reactant gases?

Answer 31

The particles are closer together and so there are more frequent successful collisions

Question 32

What is the effect of temperature on rate?

Answer 32

The higher the temperature, the faster the reaction

Question 33

Why does rate increase with temperature?

3

Answer 33

Particles have more energy and so a greater proportion of the collisions are successful.

The particles also move faster and so collsions are more frequent.

Therefore, more frequent successful collisions

Question 34

What is the effect of a catalyst on rate?

Answer 34

A catalyst increases the rate of a reaction but is not used up

Question 35

Why does rate increase with a catalyst added?

Answer 35

It provides an alternative route/mechanism with a lower activation energy and therefore a greater proportion of the collisions are successful