Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Chemistry > Kinetics > Flashcards

Kinetics Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

What is collision theory?

A

The idea that particles need to collide in the right direction and collide with energy that is at least equal to the activation energy in order to react.

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

……… ……….. distribution

A

Maxwell-Boltzmann

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

Why does the Maxwell Boltzman Distribution graph start at (0,0)?

A

Because no molecules have 0 energy

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

Most probable energy,…..

A

Mean energy, activation energy

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

What does increasing the concentration of reactants do to the rate of reaction?

A

Speeds up the rate of the reaction

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

Why does increasing the concentration of reactants in a solution increase the rate of reaction?

A

Because when you increase the concentration of reactants in a solution, there’ll be more particles in a given volume of the solution, so the particles will collide more frequently. If there are more collisions, they’ll have more chances to react

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

What does increasing the pressure do to the rate of reaction?

A

Increasing the pressure speeds up the rate of the reaction, if any of your reactants are gases

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

Why does increasing the pressure speed up the rate of reaction?

A

Because at higher pressures, there’s more particles in a given volume of gas and this increaes the frequency of successful collisions

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

What do catalysts speed up the rate of reaction?

A

Because they lower the activation energy by providing an alternate reaction pathway. Lowering the activation energy ensures that more particles will have enough energy to reach

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

What will molecules with energy greater than the activation energy do?

A

Collide with enough energy to result in a reaction

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

What 5 things impact the rate of reaction?

A
  • Concentration
  • Temperature
  • Pressure
  • Surface area
  • Catalysts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why does increasing the temperature increase the rate of reaction ?

A

Because particles gain more kinetic energy and so move around faster. This results in more frequent successful collisions occurring between particles with a high enough activation energy.

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

What does the area under the curve represent?

A

The total number of molecules, the area under thr curve will always remain the same

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

What happens to the Maxwell Boltzmann distribution curve when you increase the temperature?

A

It becomes lower and shifts to the right because a greater proportion of molecules have energy greater than or equal to the activation energy.

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

Do increasing the concentration and pressure change the shape of the Maxwell Boltzmann distribution curve?

A

No, only the temperature does

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

Why does increasing the surface area increase the rate of reaction?

A

Because this increases the number of exposed reactant particles and so there’s more frequent and successful collisions that occur

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

What happens to the position of activation energy on a Maxwell Boltzmann distribution curve when you use a catalysts?

A

Although the curve will be unchanged in shape, the position of the activation energy will shift to the left so that a greater proportion of molecules will have sufficient energy in order to react

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

Draw graphs of amount of reactant or product against time to work out the gradient which is equivalent to….

A

The rate of reaction

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

Gradient=

A

Change in y/ Change in x

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the gradient at time=0 called?

A

Thr initial rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What can the units for rate of reaction be?

A

Cm³ min-¹ OR cm³ sec-¹

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How can you work out the initial rate of reaction?

A

By calculating the gradient at time=0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Most rate of reaction graphs are volume or concentration against time. T/F?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What equation do you use to work out rates of reaction from experimental data?

A

Rate of reaction= amount of reaction used or amount of product formed/ time taken

25
Q

Is a catalyst unchanged at the end of a reaction?

A

Yes. The catalyst remains unchanged

26
Q

What are heterogeneous catalysts?

A

Catalysts that are in a different phase or state to the species in a reaction

27
Q

What’s an example of a heterogeneous catalyst in use?

A

The gases passed over a solid iron catalyst in the Haber Process

28
Q

How do solid heterogeneous catalysts work?

A
  • Reactant molecules arrive at the surface and bond with the solid catalyst. This is called adsorption.
  • The bonds between the reactant’s atoms are weakness and break up. This firms radicals, which get together to make new molecules
  • The new molecules are then detached from the catalyst. This js called desorption
29
Q

What is a homogeneous catalyst?

A

Catalysts that are in the same physical state to the reactants. Usually a homogeneous catalyst is an aqueous catalyst for a reaction between 2 aqueous solutions

29
Q

Why do loads of industries rely on catalysts?

A

Because they lower production costs as they give more product in a shorter amount of time

30
Q

Why is an iron catalyst used in the production of ammonia?

A

Because if it wasn’t for the catalyst, the temperature would have to be raised significantly in order for the reaction to happen quickly enough. This would be very expensive.

Also, it would reduce the amount of ammonia produced since the reaction is reversible, and exothermic in the direction of the ammonia production.

31
Q

What is the order of a reaction?

A

The power to which a concentration is raised to in the rate equation. It tells us how much the concentration of the substance affects the rate

32
Q

What is 0 order?

A

changes in concentration that have no effect on the rate i.e if [A] doubles and the rate doesnt change

32
Q

What is 1st order?

A

changes in concentration that have a proportional change on the rate i.e if [A] doubles and the rate subsequently doubles

33
Q

What is 2nd order?

A

changes in concentration that have a squared proportional change on the rate i.e if [A] doubles and the rate quadruples (2^2)

34
Q

What does the rate equation do??

A

It links rate with the concentration of substances

35
Q

What is the rate equation?

A

rate = k[A][B] (A and B will be raised to certain powers)

36
Q

What are the units of rate in the rate equation?

A

mol dm^-3 s^-1

37
Q

What are the units of concentration in the rate equation?

A

mol dm³

38
Q

How do you work out the units?

A

1) Add the powers

2) You multiply (mol dm-3 ) by the overall power

3) Divide (mol dm^-3 s^-1) by the concentration value

39
Q

the steeper the line….

A

the faster the rate of reaction

40
Q

why do many reactions slow down over time?

A

due to there being less reactant particles as time goes on and so
less frequent successful collisions between reactant particles.

41
Q

in some reactions, does a catalyst appear in the rate equation?

A

yes

42
Q

what is k?

A

the rate constant for a reaction

43
Q

what is the only thing that affects the value of k ?

A

temperature, as k increases with temperature

44
Q

If a reaction mechanism has a series of steps, then what is the rate of reaction dependant on?

A

the rate of slowest step

45
Q

what is the slowest step called?

A

the rate determining step (RDS)

46
Q

what does the Arrhenius equation show?

A

the link between the rate constant, activation energy and temperature.

47
Q

As the activation energy gets bigger, what happens to the rate constant ?

A

It gets smaller

48
Q

A large activation energy means a slow…….

A

Rate

49
Q

What happens when the temperature rises?

A

The rate constant increases as well

50
Q

What is a clock reaction an example of?

A

An initial rates method

51
Q

What do you measure in a clock reaction?

A

How the time taken for a set amount of product to form changes as you vary the concentration of one of the reactants .

52
Q

In the clock reaction, why will there be a sudden increase in the concentration of a certain product?

A

Because a limiting reactant will have been used up

53
Q

The quicker the clock reaction finsihes….

A

The faster the initial rate of the reaction

54
Q

when carrying out a clock reaction, what assumptions do you need to make?

A
  • That the concentration of each reactant doesn’t change significantly over the time period of your clock reaction.
  • That the temperature stays constant
  • That when the endpoint is seen, the reaction has not proceeded too far.
55
Q

What is the iodine clock reaction also known as?

A

the Harcourt-esson reaction

56
Q

In an iodine clock reaction, what reaction are you monitoring?

A

H20 + 2I- + 2H+-> 2H20 + I2

57
Q

How do you carry out the iodine clock reaction in the lab to find the order with respect to potassium iodide?

A

1) Rinse a clean pipette with sulfuric acid. Then, use the pipette to transfer a small amount of sulfuric acid of a known concentration to a clean beaker.

2) Using a clean pipette or measuring cylinder, add distilled water to the beaker containing the sulfuric acid.

3) Using a dropping pipette, add a few drops of starch to the same beaker.

4) Measure a known amount of potassium iodide solution of a known concentration using either a pipette or burette. Transfer this volume to the reaction vessel.

5) Add sodium thiosulfate to the reaction vessel. Swirl the contents of the beaker to ensure that all of the solutions are evenly mixed.

6) Transfer hydrogen peroxide solution to the reaction vessel, whilst stirring the vessel and starting a stopwatch.

7) Continue to stir and stop the stopwatch when the contents of the beaker turn from colourless to blue black. Record this time in a results table, along with the quantities of sulfuric acid, water, potassium iodide, and sodium thiosulfate solutions you used in that experiment.

8) Repeat the experiment, varying the volumes of potassium iodide solution.

9) Keep the volume of sulfuric acid, sodium thiosulfate, and hydrogen peroxide constant and use varying amounts of distilled water in each experiment so that the overall volume of the reaction mixture remains constant.

A-level Chemistry (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions