3.2.2: Reaction rates Flashcards

1
Q

What is the equation used to calculate rate?

A

Rate = change in concentration / time

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

What is the unit for rate of reaction?

A

mol dm-3 s-1

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

What must particles do in order to react?

A

Collide with sufficient energy (activation energy) and the correct orientation

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

Do most collisions result in a reaction?

A

no

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

What are the factors that affect rate of reaction?

A
● Temperature
● Pressure
● Concentration
● Surface area
● Catalyst
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the effect of increasing temperature on rate of reaction and why?

A

Increasing temperature → increased rate of reaction
Much higher proportion of particles have energy greater than the activation energy → many more successful collisions per second →increased rate

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

What is the effect of increasing concentration/pressure on rate of reaction and why?

A

Increased concentration/pressure → increased rate of reaction
There are more particles in a given volume → more frequent successful collisions → increased rate

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

What are the variables in an experiment that can be monitored to calculate the rate of reaction?

A

● Concentration of reactant or product
● Gas volume of products
● Mass of substances formed

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

How to calculate rate from a concentration time graph?

A

Draw a tangent
Work out the gradient of the tangent using the equation
Gradient = change in y / change in x

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

What is a catalyst?

A

A substance which increases the rate of reaction but is not used up in the reaction

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

How do catalysts work and how do they increase the rate of reaction?

A

They provide an alternate reaction pathway (with a lower activation energy)
Due to lower activation energy, more particles have energy > activation energy, so more frequent successful collisions, so increased reaction rate

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

What does homogeneous catalyst mean?

A

A catalyst that is in the same phase as the reactants.

Eg. liquid catalyst mixed with liquid reactants

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

What does heterogeneous catalyst mean?

A

Catalyst used in the reaction is in
different phase to the reactants
Eg. gaseous reactants passed over solid
catalyst

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

What are catalytic convertors?

A

They are present in vehicles to reduce toxic emission and prevent photochemical smog

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

Define activation energy

A

The minimum energy that particles must

collide with for a reaction to occur

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

Name some important features of Boltzmann distribution (5 marks)

A

● Area under the curve = total number of molecules
● Area under the curve does not change when conditions alter
● The curve starts at the origin
● Curve does not touch or cross the energy axis
● Only the molecules with energy greater than activation energy can react

17
Q

What are the axis in a Boltzmann distribution?

A

X axis - energy
Y axis - number of molecules with a
given energy