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A-LEVEL CHEMISTRY > A6 Kinetics II > Flashcards

A6 Kinetics II Flashcards

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1
Q

Define Rate of Reaction

A

Change in quantaties of reactants or products over time

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2
Q

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

A

Changing the concentration will have no effect on rate

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3
Q

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

A

Concentration is proportional to rate

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4
Q

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

A

Concentration is proportional to rate (^2)

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5
Q

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

A
  • 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
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6
Q

What will always be included in the rate equation

A

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

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7
Q

How are 0th order reactants included in rate equations

A

They are not

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8
Q

How are 1st order reactants included in rate equations

A

To the power of 1 (by itself)

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9
Q

How are 2nd order reactants included in rate equations

A

Squared

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10
Q

Define Overall Order

A

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

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11
Q

How to determine the overall order of a reaction

A

The sum of the orders of the reactants

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12
Q

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

A

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

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13
Q

What will the unit for rate always be

A

dm -3 mol s-1

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14
Q

What will the unit for K always contain

A

s-1

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15
Q

How should answers in kinetics always be written

A

dm then mol then s

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16
Q

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

A

A reactant that is first order

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17
Q

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

A

A reactant that is 0tt order

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18
Q

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

A

Line where consecutive half-lives are constant

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19
Q

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

A

Straight line, with a constant negative gradient

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20
Q

Define half-lives

A

Time taken for the concentration of a reactant to half

21
Q

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

A

The reaction is 1st order with respect to the reactant

22
Q

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

A

When the reaction is first order with respect to the reactant

23
Q

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

A
24
Q

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

A

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

25
Q

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

A

A 0th order reactant

26
Q

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

A

A 1st order reactant

27
Q

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

A

A 2nd order reactant

28
Q

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

A

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

29
Q

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

A

A horizontal line, with a gradient of 0

30
Q

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

A

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

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

To ensure that the concentration is constant throughout

34
Q

When is colorimetry used experimentally in initial rates reactions

A

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

35
Q

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

A

Absorbancy decreases as concentration decreases

36
Q

Define rate-determining step

A

The slowest step of the reaction

37
Q

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

A

Only those from the rate-determining step

38
Q

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

A

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

39
Q

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

A

The mechanism is consistent with the rate equation

40
Q

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

A
  • Stochiometry in the rate equation doesn’t match stochiometry in overall equation
  • Successful collisions are unliekl with more than two particles
41
Q

For Arrhenius graph, how is the Ea determined

A
42
Q

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

A
  • 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
43
Q

Equation for determining activation energy from an Arrhenius graph

A
44
Q

Units for gradient on Arrhenius graph

A

K

45
Q

What does the y-intercept of an arrhenius graph represent

A

ln A

46
Q

How to determine A from an Arrhenius graph

A

e (to the power of intercept number)

47
Q

Equation for ln K of Arrhenius graph

A
48
Q

How to determine ln K from an Arrhenius graph

A
49
Q

Units for horizontal line of Arrhenius graph

A

K (-1)

A-LEVEL CHEMISTRY (11 decks)

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