OZ4: Rates of Reaction Flashcards

1
Q

What is meant by the “rate of reaction”?

A

How quickly reactants are converted into products

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

Give the formula for calculating the rate of reaction.

A

Change in property/time taken

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

Give 5 ways change in property can be measured to determine rate of reaction.

A
  • Chemical analysis
  • Volume of gases
  • Mass changes
  • PH measurement
  • Calorimetery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why is it important for scientists to measure rates of reactions?

A
  • A reaction occurring too quickly can be dangerous

- A reaction occurring too slowly is impractical because it ties up equipment and people, which costs money

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

Give an example in which the volume of a gas is measured to determine rate of reaction.

A
  • Reaction between calcium carbonate and HCl produces CO2

- Gas is collected in a measuring cylinder

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

Give an example in which mass change is measured to determine rate of reaction.

A
  • Reaction between calcium carbonate and HCl produces CO2

- Mass lost of calcium carbonate can be recorded against time

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

Give an example in PH is measured to determine rate of reaction.

A
  • Reaction between calcium carbonate and HCl produces CO2

- HCl concentration falls so the PH of the reaction mixture also falls

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

What does a calorimeter do?

A

Measures change in a reaction’s colour

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

Give an example where calorimetery is used to determine rate of reaction.

A
  • When zinc reacts with copper (II) sulphate, the blue coloration of copper sulphate decreases
  • Measure the rate of this colour decreasing against time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Explain how chemical analysis can determine the rate of reaction.

A
  • Involves taking samples of the reaction mixture at regular intervals
  • Stopping reaction in a sample (quenching) before analysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Give an example in which chemical analysis is used to determine rate of reaction.

A
  • Iodine and propanone react in the presence of an acid catalyst
  • The sample is extracted and quenched by adding sodium hydrogen carbonate, neutralising the acid
  • Amount of iodine remaining is determined by titration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do you plot a graph for the rate of reaction?

A
  • Time is plotted on the x axis

- Change in property is plotted on the y axis

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

Give the conditions for a successful collision.

A
  • Must collide in the right direction
  • Must collide with correct orientation
  • Must collide with the minimum amount of Kinetic energy required
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are liquid and gas particles always doing?

A

Always moving and colliding

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

Why is initial reaction the fastest?

A
  • As the reaction continue, the concentration of reactants decreases
  • Less frequent collisions between reactant particles
  • Decreased rate of reaction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does an increased rate of reaction mean in terms of collisions?

A

Increase in collisions in a given time between reacting particles

17
Q

Define “activation energy”

A

The minimum amount of kinetic energy required by a pair of colliding particles before a reaction occurs

18
Q

What is activation energy needed for?

A

To make or break bonds

19
Q

What happens at the highest point of an enthalpy profile diagram?

A

Transition state:

  • Old bonds stretch and break
  • New bonds form
20
Q

In an exothermic enthalpy profile are the reactants higher up or lower down than the products?

21
Q

In an endothermic enthalpy profile are the reactants higher up or lower down than the products?

22
Q

What does a Maxwell-Boltzmann Distribution graph show?

A

The distribution of different kinetic energies in a gas

23
Q

What does the area under a Maxwell-Boltzmann Distribution graph represent?

A

The number of molecules

24
Q

Are there more particles on the left or the right side of a Maxwell-Boltzmann Distribution graph?

A

On the right side

25
Where on a Maxwell-Boltzmann Distribution graph is the max number of particles with a specific energy?
In the middle on the highest peak on the graph
26
Where on a Maxwell-Boltzmann Distribution graph is the average energy shown?
In between the middle and Ea on the graph
27
What factors influence rate of reaction?
- Temperature - Radiation intensity - Concentration/pressure - Catalyst - Particle size
28
How does increased temperature increase rate of reaction?
- Increased temperature, means particles on average have more kinetic energy and will move faster - A greater proportion of molecules will have the activation energy and will react - So there will be a higher frequency of collisions which involve energy equal to activation energy - So there will be more successful collisions in a given time (e.g per second)
29
How does increased temperature change a Maxwell-Boltzmann Distribution graph?
- The peak of the curve is lower - Graph is shifted to the right - But same total area under the graph
30
Why is the peak of the curve shifted lower?
To balance out other areas of the graph increasing so there is a same total area under the graph
31
What happens to the most probable and average energy when temperature increases?
They also increase
32
How does the amount of particles with the greater than/same energy as activation energy?
More particles
33
How does increased concentration/pressure increase rate of reaction?
- Particles are closer together on average - More particles per cm^3 - So they collide more often, leading to more successful collisions per second
34
How does increased concentration/pressure change a Maxwell-Boltzmann Distribution graph?
- Area under the graph is bigger because they are more molecules - So same shape of graph but the curve is higher up
35
How does particle size increase rate of reaction?
- Powder is better than a lump | - Because there is a greater surface area making collisions more likely
36
How does a catalyst increase rate of reaction?(2)
- Provides an alternative pathway for a reaction | - with a lower activation energy
37
How does using a catalyst change a Maxwell-Boltzmann Distribution graph?
- Put the Ea line further up the graph | - Because at any given temperature, a larger proportion of particles collide successfully