Ib Chemistry Chapter 6

Front 1

1. What is chemical kinetics?

Back 1

The study of factors affecting the rate of a chemical reaction

Front 2

2. Define rate of a chemical reaction

Back 2

Increase in concentration of one of products/time or decrease in concentration of one of reactions/time

Front 3

3. What is the unit for rate of reaction?

Back 3

Mol/dm3/s

Front 4

4. What four factors can be measured to find the change in concentration?

Back 4

Mass/volume changes, absorption using a spectrometer, electrical conductivity and pH changes

Front 5

5.

Front 6

6. What does a Maxwell-Boltzmann curve show?

Back 6

The distribution of kinetic energies

Front 7

7. How does the curve change as temperature rises

Back 7

There are more particles with the activation energy and the average temp is greater

Front 8

8. What are the 3 conditions needed for a reaction?

Back 8

Particles must collide, they must collide with the appropriate geometry and they must collide with sufficient energy

Front 9

9. How does temp affect the rate of reaction?

Back 9

As temp goes up, so does number of particles possessing activation energy -> more successful collisions. Increase in 10 deg doubles rate of reaction

Front 10

10. How does SA affect the rate of reaction?

Back 10

Larger SA increases rate of reaction

Front 11

11. How does concentration affect the rate of reaction?

Back 11

Higher concentration means more collisions per second. As reaction happens, concentration decreases so reaction slows

Front 12

12. How does the use of a catalyst affect the rate of reaction?

Back 12

Bring the reactive parts of reactant particles in close contact. More of the reactants will possess the lower activation energy, so rate of reaction increases

Front 13

13. What is the rate of reaction proportional to?

Back 13

Concentration of both reactants, each raised to a power

Front 14

14. What is the expression for the rate of reaction?

Back 14

Rate = k[A]x[B]y

Front 15

15. What is k?

Back 15

The constant of proportionality or rate constant

Front 16

16. What is x?

Back 16

The order of reaction with respect to A

Front 17

17. What is y?

Back 17

The order of reaction with respect to B

Front 18

18. What is the overall order of the reaction?

Back 18

x+y

Front 19

19. What do the units of the rate depend on?

Back 19

The overall order of the reaction

Front 20

20. What are the units in the first order?

Back 20

Rate = k[A]  K = rate/[A]  (mol/dm3/s) / mol/dm3 = s-1

Front 21

21. What are the units for the second order?

Back 21

Rate = k[A]2 or k=[A][B]  k = rate/[A]2  units = dm3 mol-1 s-1

Front 22

22. What are the units for the third order?

Back 22

Rate = k[A]2[B] or rate = k[A][B]2  k = rate /[A]2[B] = dm6mol-2s-1

Front 23

24. What does k[A] denote?

Back 23

The rate of change of concentration of A

Front 24

25. How else can k[A] be written?

Back 24

(d[A])/dt

Front 25

26. What is the integrated form of the rate equation?

Back 25

kt = ln [A0] - ln[A] where [A0] = the initial concentration and [A] is the concentration at time t

Front 26

27. Define half-life

Back 26

the time taken for the concentration of a reactant to fall to half its original value

Front 27

28. Define the integrated expression at time t1/2

Back 27

kt1/2 = ln[A]0 – ln1/2[A]0 = ln2, and since ln2 = 0.693, t1/2 = 0.693/k

Front 28

29. First order reactions have a constant half-life

Front 29

30. What is the rate-determining step?

Back 29

The slowest step of a reaction which determines the rate of the whole reaction

Front 30

31. What is a unimolecular process?

Back 30

When a single species breaks down into two or more products

Front 31

32. What is a bimolecular process?

Back 31

When two species can collide and interact

Front 32

33. What is an activated complex?

Back 32

A mixture of an association of the reacting particles in which bonds are in the process of being broken and formed

Front 33

34. What does an activated complex do?

Back 33

It either breaks down to form the products or reverts back to the original reactants

Front 34

35. What is the molecularity of a reaction?

Back 34

The number of species taking part in any step in the reaction

Front 35

36. What does molecularity refer to in most cases?

Back 35

The rate-determining step

Front 36

37. What is the molecularity of the reaction between 2NO(g) + 2H2 (g) N2 (g) + 2H2O(g)?

Back 36

2, as the 2 reacting species are involved in the rate determining step

Front 37

38. When is the rate constant?

Back 37

If the temperature remains constant

Front 38

39. What happens to the rate constant if the temp increases?

Back 38

The rate constant increases

Front 39

40. What is the Arrhenius equation?

Back 39

k = Ae( - Ea/RT)

Front 40

41. What does the Arrhenius equation show?

Back 40

The relationship between the rate constant and the temperature

Front 41

42. What is E¬a?

Back 41

Activation energy

Front 42

43. What is R?

Back 42

The gas constant

Front 43

44. What is A?

Back 43

The frequency factor

Front 44

45. What does A indicate?

Back 44

The frequency of collisions with the correct orientation for the reaction

Front 45

46. What is the equation in its logarithmic form?

Back 45

Ln(k) = (-Ea/RT) + ln(A)

Front 46

47. What can the equation be used to determine?

Back 46

The frequency factor and the activation energy for the reaction