A6 Kinetics II

Question 1

Define Rate of Reaction

Answer 1

Change in quantaties of reactants or products over time

Question 2

What does it mean if the reaction is 0th order with respect to a reactant

Answer 2

Changing the concentration will have no effect on rate

Question 3

What does it mean if the reaction is 1st order with respect to a reactant

Answer 3

Concentration is proportional to rate

Question 4

What does it mean if the reaction is 2nd order with respect to a reactant

Answer 4

Concentration is proportional to rate (^2)

Question 5

When given a table to determine the reaction order with respect to a reactant, what must always be included in the explaination of each reactant

Answer 5

• From experiment X to Y
• How the concentration of each reactant changes
• How the rate changes
• The reaction will be 0th/1st/2nd order with respect to the reactant

Question 6

What will always be included in the rate equation

Answer 6

Rate = k [reagents that are 1st or 2nd order]

Question 7

How are 0th order reactants included in rate equations

Answer 7

They are not

Question 8

How are 1st order reactants included in rate equations

Answer 8

To the power of 1 (by itself)

Question 9

How are 2nd order reactants included in rate equations

Answer 9

Squared

Question 10

Define Overall Order

Answer 10

Overall effect of the concentrations of all reactants on the rate of reaction

Question 11

How to determine the overall order of a reaction

Answer 11

The sum of the orders of the reactants

Question 12

How can the rate constant, K , be determined from a rate equation

Answer 12

Re-arrange so that K = rate / [reactants]

Question 13

What will the unit for rate always be

Answer 13

dm -3 mol s-1

Question 14

What will the unit for K always contain

Answer 14

s-1

Question 15

How should answers in kinetics always be written

Answer 15

dm then mol then s

Question 16

What does the red line represent on this concentration-time graph

Answer 16

A reactant that is first order

Question 17

What does the blue line represent on this concentration-time graph

Answer 17

A reactant that is 0tt order

Question 18

Describe the line on a concentration-time graph, that is 1st order

Answer 18

Line where consecutive half-lives are constant

Question 19

Describe the line on a concentration-time graph, that is 0th order

Answer 19

Straight line, with a constant negative gradient

Question 20

Define half-lives

Answer 20

Time taken for the concentration of a reactant to half

Question 21

On a concentration-time graph, what does it mean if a reactant has constant consecutive half-lives

Answer 21

The reaction is 1st order with respect to the reactant

Question 22

When can the value of K be determined from a concentration-time

Answer 22

When the reaction is first order with respect to the reactant

Question 23

What is the formula for K when calculating with a 1st order concentration-time graph

Answer 23

Question 24

What is an alternative to using the following formula to determine K on a 1st order concentration time graph

Answer 24

Drawing a tangent to the line at t=0s, and determining the gradient

Question 25

What does the blue line represent on this rate-concentration graph

Answer 25

A 0th order reactant

Question 26

What does the red line represent on this rate-concentration graph

Answer 26

A 1st order reactant

Question 27

What does the green line represent on this rate-concentration graph

Answer 27

A 2nd order reactant

Question 28

Describe a 1st order reactant on a rate-concentration graph

Answer 28

Line that goes through the origin, with a constant positive gradient

Question 29

Describe a 0th order reactant on a rate-concentration graph

Answer 29

A horizontal line, with a gradient of 0

Question 30

Describe a 2nd order reactant on a rate-concentration graph

Answer 30

A curve that has a gradient that gets more positive, as concentration increases

Question 31

When investigating initial rate, what should be ensured when the reaction is 0th order to a reactant

Answer 31

A large excess of it is used, to ensure that the concentration is constant throughout

Question 32

What must be ensured when investigating initial rate with reactants that are 0th order

Answer 32

A large excess of it is used, to ensure that the concentration is constant throughout

Question 33

Why is a large excess of a 0th order reactant used when determining initial rate experimentally

Answer 33

To ensure that the concentration is constant throughout

Question 34

When is colorimetry used experimentally in initial rates reactions

Answer 34

When one of the reactants is coloured (E.g iodine solution is orange)

Question 35

What is the trend with abosrbancy (measured with a colorimeter) when a reactant is coloured

Answer 35

Absorbancy decreases as concentration decreases

Question 36

Define rate-determining step

Answer 36

The slowest step of the reaction

Question 37

Of all the reactants in an equation, what reactants will the rate equation include

Answer 37

Only those from the rate-determining step

Question 38

How to tell that a mechanism is consistent with the rate equation

Answer 38

When all the mechanism steps (before and including the rate determining step) together give the reactants and products in the same stochiometric ratio as in the rate equation

Question 39

When all the mechanism steps (before and including the rate determining step) together give the reactants and products in the same stochiometric ratio as in the rate equation

Answer 39

The mechanism is consistent with the rate equation

Question 40

Why would a two-step mechanism be unlikely to occur in one step

Answer 40

* Stochiometry in the rate equation doesn't match stochiometry in overall equation * Successful collisions are unliekl with more than two particles

Question 41

For Arrhenius graph, how is the Ea determined

Answer 41

Question 42

Draw a Maxwell-Boltzmann graph, and show and explain how an increased temperature would affect this

Answer 42

* Increasing temperature means that there is a greater area under the curve above the activation energy * A greater number of molecules have energy greater than the activation energy

Question 43

Equation for determining activation energy from an Arrhenius graph

Answer 43

Question 44

Units for gradient on Arrhenius graph

Answer 44

K

Question 45

What does the y-intercept of an arrhenius graph represent

Answer 45

ln A

Question 46

How to determine A from an Arrhenius graph

Answer 46

e (to the power of intercept number)

Question 47

Equation for ln K of Arrhenius graph

Answer 47

Question 48

How to determine ln K from an Arrhenius graph

Answer 48

Question 49

Units for horizontal line of Arrhenius graph

Answer 49

K (-1)