Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Physical Chemistry > Reaction Rate, Reaction Order & Rate constant > Flashcards

Reaction Rate, Reaction Order & Rate constant Flashcards

1
Q

What do reaction mechanisms consist of?

A

A series of elementary reaction steps that make up the overall reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the rate of reaction expressed as?

A

A change of the concentration of a given reactant (or product) as a function of time:

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What factors influence the rate of reaction?

A
  1. Concentration of reactants
  2. Temperature and pressure of the
  3. Solvent (polarity, ionic strength)
  4. Surface area of a solid reactant
  5. Action of catalysts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the rate law?

A

Relation between rate reaction and the reactant concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the rate constant dependent on?

A

Independent of concentrations but depends on T or P. Units depends on the overall order of the reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the rate law of a zero-order reaction?

A

Reaction proceeds at constant arte and is independent of the reaction concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the units of k for a zero-order reaction?

A

Concentration.time-1

mol.L-1.s-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is half-life?

A

The half (t1/2) of a reaction is the time taken for the concentration of reactant to fall to half of its original value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the shell-life (t0.9 or t10%)?

A

Is the length of time the product may safety be stored on the dispensary shelf before significant decomposition occur. It is the time taken for decomposition of 10% of the active drug to occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the rate law of a first order reaction?

A

Rate depends on the concentration of one reactant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the unit of a first- order reaction?

A

Units of k: time-1

s-1 (or similar)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the plot of the logarithms of the concentration of the analyse (as ordinate) against time (as abscess) for a zero and first order reaction?

A

Linear with a gradient of -k

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the rate constant in a second-order type I reaction?

A

Rate depend on the product of two concentration terms which refer to same reactant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are units of k for a second order type I reaction?

A

Concentration-1.time-1

L.mol-1.s-1 (or similar)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the plot of the inverse of the concentration of the analyse (as ordinate) against time (as abscess) for a second order type I reaction?

A

Linear with a gradient of k

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the rate law for a second order reaction type II?

A

Rate depends on the product of two concentration terms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is Pseudo first order?

A

Rate depends on the concentration of one reactant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the units for a second order reaction?

A

Units of k: time-1

Ex: s-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the units of Ea?

A

J.mol-1 (R= 8.31 J.K-1)

20
Q

What are the units of T?

21
Q

What are the units of A?

A

Units of the rate constant

22
Q

What is happens to the half-life for n=0?

A

It increases with increasing concentration

23
Q

What happens to the half-life for n=1?

A

It does not change with change in concentration

24
Q

What happens to the half-life for n=2?

A

Decreases with increasing concentration

25
What must reactant molecules do in order to react?
Must collide with the appropriate orientation and with a minimum energy
26
What is activation energy?
Minimum energy needed for the reaction to occur. Ea comes from the thermal excitation of molecules
27
What does a large Ea mean?
Strong T dependence and a slow reaction
28
What does a small Ea mean?
Weak T dependence and a fast reaction
29
What is a catalyst?
Speeds up a reaction by providing an alternate reaction mechanism with a lower energy of activation compare to the unanalysed pathway
30
How is the rate changed?
By lowering Ea
31
What can enzymes do to a reaction rate?
Increase the A factor | Decrease the energy of activation. Increase the reaction rate without increasing the temperature
32
What mechanism describes the behaviour of many enzymes?
Michaelis-Mennen mechanism
33
What is Km?
A constant. It is the concentration of substrate [S] required to reach half-maximal velocity (Vmax/2). Under true conditions it is the estimate of the dissociation constant of the ES complex
34
What does a small Km mean?
Tight binding between E and S
35
What does a large Km mean?
Weak binding between E and S
36
What is Vmax?
A constant. Is the theoretical maximal rate of the reaction but it is never achieved in reality. Vmax is asymptotically approached as substrate is increased.
37
What would need to be required to reach Vmax?
All enzymes molecules to be tightly bound with substrate
38
What is kcat?
Turnover number. It is the number of substrate molecules converted to product per unit of time and per enzyme molecule (when E is saturated with S). It a measure of the catalytic activity of the enzyme
39
What is kcat/Km?
The catalytic efficiency. It is an estimate of "how perfect" the enzyme is. It is used to rank enzymes
40
What does a big kcat/Km mean?
That an substrate binds tightly to E (small Km), with a fast reaction of ES complex.
41
What is reversible competitive inhibition?
The substrate and the inhibitor are chemically similar. S and I compete for binding to the same active site: S and I cannot bind to the enzyme at the same time
42
What can overcome reversible competitive inhibition?
Increasing [S]
43
What happens to the constants in reversible competitive inhibition?
``` Maximum velocity (Vmax) unchanged Km is increased ```
44
What is non competitive inhibition?
When the substrate and the inhibitor are not similar. I does not bind to the active site of the enzyme. I binds equally well to both free E and the enzyme-substrate complex. Increasing [S] cannot overcome inhibition
45
What happens to the constants in reversible non competitive inhibition?
Km unchanged | Vmax is decreased

Physical Chemistry (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions