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Rate Equations PHYSICAL Flashcards

1
Q

What does rate of reaction refer to?

A

Change in amount or concentration of reactant or product per unit time

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2
Q

How can rate of reaction be found?

A

Measuring decrease in concentration of reactant over time
Measuring increase in concentration of product over time

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3
Q

What are the units for rate of reaction?

A

mol dm⁻³ s⁻¹

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4
Q

What is the general equation for rate of reaction?

A

k [A]ᵐ [B]ⁿ

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5
Q

What are [A] and [B] in the general equation for rate of reaction?

A

Concentrations of reactants

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6
Q

What are m and n in the general equation for rate of reaction?

A

Orders of reaction

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7
Q

What orders do reactant concentrations have?

A

0, 1 or 2

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8
Q

What does the order of reactant concentrations depend on?

A

Effect on rate of reaction

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9
Q

Why are products not involved in rate equation?

A

No effect on rate of reaction

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10
Q

How is order determined?

A

Experimentally

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11
Q

When would a catalyst appear in a rate equation?

A

Measurable and quanitifiable effect on rate of reaction
Homogeneous catalyst
Chemical appears in rate equation not as reactant

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12
Q

What does the order of reactant represent?

A

How concentration of reactant affects rate of reaction

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13
Q

What is meant when the order of a reactant is 0?

A

No effect on rate of reaction

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14
Q

What is meant when the order of a reactant is 1?

A

Rate is directly proportional to concentration of reactant

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15
Q

What is meant when the order of a reactant is 2?

A

Rate is directly proportional to square of concentration of reactant

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16
Q

Which orders are included in rate equations?

A

1 and 2

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17
Q

What is the overall order of reaction?

A

Sum of powers of reactants in rate equation

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18
Q

What is meant by half-life?

A

The time taken for concentration of a limiting reactant to become half of its initial value

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19
Q

What is the relationship between concentration of reactant and time for zero-order?

A

Concentration of reactant is inversely proportional to time
Concentration of reactant decreases as time increases

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20
Q

What does a concentration-time graph for a zero-order reaction look like?

A

Straight line going diagonally down

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21
Q

What is the relationship between concentration of reactant and time for first-order?

A

Concentration of reactant decreases with time

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22
Q

What does a concentration-time graph for a first-order reaction look like?

A

Curve going downwards
Eventually plateaus

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23
Q

What is the relationship between concentration of reactant and time for second-order?

A

Concentration of reactant decreases more steeply with time

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24
Q

What does a concentration-time graph for a second-order reaction look like?

A

Curve going more steeply downwards
Plateaus sooner

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25
How does concentration affect rate in a zero-order reaction?
No affect Remains constant
26
What does a rate-concentration graph for a zero-order reaction look like?
Horizontal line
27
How does concentration affect rate in a first-order reaction?
Rate is directly proportional to concentration of reactant Increase by same factor
28
What does a rate-concentration graph for a first-order reaction look like?
Straight diagonal line
29
How does concentration affect rate in a second-order reaction?
Rate is directly proportional to square of concentration of reactant Increase by factor squared
30
What does a rate-concentration graph for a second-order reaction look like?
Curved line upwards
31
What is the rate equation for zero-order reactant?
rate = k
32
What is the rate equation for first-order reactant?
rate = k [A]
33
What is the rate equation for first-order reactant?
rate = k [A]²
34
Which reactant does half-life refer to?
Limiting reactant
35
What is the relationship between half-life and time for a zero-order reaction?
Successive half-lives decrease with time Takes less time for concentration of reactant to halve as progresses
36
What is the relationship between half-life and time for a first-order reaction?
Remains constant throughout reaction Takes same time for concentration of reactant to halve as progresses
37
What is the relationship between half-life and time for a second-order reaction?
Half-life increases with time Takes more time for concentration of reactant to halve as progresses
38
What does k represent in rate equation?
Rate constant
39
How can the rate equation be derived for a reaction?
Determine all orders individually Identify two experimenets where concentration of reactant changes and others remain constant Repeat for all reactants and find order with respect to all reactants
40
How is rate constant (k) calculated?
Using initial rates and rate equation
41
What is the equation for rate constant?
k = rate / [A]ᵐ[B]ⁿ
42
How are the units for rate constant determined?
Replace values in equations with units Combine or cancel units as required
43
How does k remain constant?
Concentration of reactants only factor changed
44
Describe the change to rate and rate constant when reaction happens at higher temperature.
Greater proportion of molecules possess activation energy Rate and rate constant directly proportional to amount of molecules Rate of reaction increases Rate constant increases
45
What equation shows the relationship between rate constant, temperature and activation energy?
k = Ae⁻ᴱᵃ/ᴿᵀ
46
What does k stand for in k = Ae⁻ᴱᵃ/ᴿᵀ?
Rate constant
47
What does A stand for in k = Ae⁻ᴱᵃ/ᴿᵀ?
Arrhenius constant
48
What does Ea stand for in k = Ae⁻ᴱᵃ/ᴿᵀ?
Activation energy
49
What does R stand for in k = Ae⁻ᴱᵃ/ᴿᵀ?
Gas constant
50
What does T stand for in k = Ae⁻ᴱᵃ/ᴿᵀ?
Temperature
51
What does e stand for in k = Ae⁻ᴱᵃ/ᴿᵀ?
Mathematical constant
52
What is Ea measured in in k = Ae⁻ᴱᵃ/ᴿᵀ?
J mol⁻¹
53
What is R measured in in k = Ae⁻ᴱᵃ/ᴿᵀ?
8.31 J K⁻¹ mol⁻¹
54
What is T measured in in k = Ae⁻ᴱᵃ/ᴿᵀ?
Kelvin
55
What are considered constants in k = Ae⁻ᴱᵃ/ᴿᵀ?
A, e, Ea and R
56
Why is A considered a constant in k = Ae⁻ᴱᵃ/ᴿᵀ?
Varies only a little with temperature
57
What is k = Ae⁻ᴱᵃ/ᴿᵀ known as?
Arrhenius equation
58
What is the arrhenius equation rearranged to?
In k = In A - Ea/RT
59
How does the arrhenius equation show the effect of increased temperature on rate of reaction?
Greater value of In k Greater value of k Increase in k means increase in rate of reaction
60
How does the arrhenius equation show the effect of increased activation energy on rate constant?
Lower proportion of molecules possess activation energy Rate of reaction decreases Value of k decreases
61
What graph can be plotted to calculate Ea?
In k against 1/T
62
How is the arrhenius equation written in the form of y = mx + c?
In k = -Ea/R 1/T + In A
63
What is the gradient in In k = -Ea/R 1/T + In A?
-Ea/R
64
What is the y intercept in In k = -Ea/R 1/T + In A?
In A
65
Why is the initial rate of a reaction used?
Exact concentrations of reactants is known
66
How is initial rate determined from experiments?
Experiments planned so result determines order for each reactant Concentration-time graph drawn for each experiment Initial rate calculated for each graph
67
How is initial rate calculated from graph?
Tangent drawn at t = 0 and gradient calculated
68
Why is there a rate determining step?
A chemical reaction can only go as fast as slowest part of reaction
69
What is a unimolecular reaction?
One species involved in rate-determining step
70
What is a bimolecular reaction?
Two species involved in rate-determining step
71
What does it mean when reactant appears in rate-determining step?
Concentration of reactant will appear in rate equation too
72
What are classed as catalysts in rate equations?
Reactants that appear in rate equation but not in chemical reaction equation
73
What is an intermediate?
Combination of two species formed in rate-determining step

Save My Exams - Chem (23 decks)

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