Section 1

Question 1

Why is controlling the rate of reaction in industrial processes important?

Answer 1

• if the reaction is too slow it takes too long so profit is lowered or the process is not economically viable
• if the process is too quick then there is a risk of thermal explosion

Question 2

What are five factors affecting the rate of reaction?

Answer 2

• concentration
• pressure
• particle size
• temperature
• catalyst

Question 3

How does increasing concentration affect the rate of reaction?

Answer 3

It increases the rate of reaction

Question 4

How does increasing pressure affect the pressure of a gaseous reaction?

Answer 4

It increases the rate of reaction

Question 5

How does decreasing the particle size affect the rate of reaction?

Answer 5

It increases rate of reaction (more surface area)

Question 6

How does increasing temperature affect the rate of reaction?

Answer 6

It increases the rate of reaction

Question 7

What does adding a catalyst do to the rate of reaction?

Answer 7

It increases the rate of reaction

Question 8

What are the two features necessary of reactants for collision theory?

Answer 8

• reactants must collide with each other in the correct orientation
• the collision must have sufficient energy

Question 9

Use collision theory to describe how concentration affects rate of reaction

Answer 9

A more concentrated acid has more particles so allows more collisions between acid and solid. More of these collisions will have sufficient energy and correct orientation for a reaction to occur and since the number of effective collisions increases the rate of reactions increases

Question 10

Use collision theory to describe how pressure affects rate of reaction

Answer 10

The higher the pressure in a gaseous reaction the closer together the particles, which leads to an increase in the number of collisions between reactants molecules. This increases the number of collisions with sufficient energy and correct orientation, so increases the rate of reaction

Question 11

Use collision theory to describe how particle size affects rate of reaction

Answer 11

Since particles can only collide with solid on the surface, more surface area in contact with the acid means more collisions per second. More of these collisions will have sufficient energy and in the correct orientation, so smaller particles increases the rate of reaction

Question 12

Use collision theory to describe how temperature affects rate of reaction

Answer 12

Acid particles in a higher temperature beaker are moving faster which leads to an increase in number of collisions with sufficient energy and in the correct orientation which increases the rate of reaction

Question 13

What does increasing the temperature by 10 degrees celcius do to the reaction rate?

Answer 13

It approximately doubles the rate of reaction

Question 14

How do you calculate the relative rate and what are the units?

Answer 14

1/time

s-1

Question 15

What is enthalpy change?

Answer 15

The energy difference between the reactants and the products

Question 16

How do you calculate enthalpy change?

Answer 16

Energy of products - energy of reactants

Question 17

What is an exothermic reaction?

Answer 17

A reaction that releases heat to the surroundings (feels hot)

Question 18

What is an endothermic reaction?

Answer 18

A reaction that takes in heat from the surroundings (feels cold)

Question 19

What is the delta H for an endothermic reaction?

Answer 19

Positive

Question 20

What type of diagram is used to show enthalpy change and what is it called?

Answer 20

Potential energy against reaction progress

Potential energy diagram or reaction profile

Question 21

What is the delta H of an ectothermic reaction?

Answer 21

Negative

Question 22

Describe the diagram used to show enthalpy change for an exothermic reaction

Answer 22

Reactants higher energy than products (both straight lines)

Line increases then decreases

Question 23

Describe the diagram used to show enthalpy change for an endothermic reaction

Answer 23

Reactants lower energy than products (both straight lines)

Like increases then decreases

Question 24

What is the activation energy of a reaction?

Answer 24

The minimum kinetic energy required by colliding particles before a reaction will occur
or:
The minimum energy required by colliding particles to form an activated complex

Question 25

How do you calculate the activation energy of a reaction?

Answer 25

Potential energy of the activated complex - Potential energy of the reactants

Question 26

What is the process from the reactants to the products?

Answer 26

The reactants collide and join together to form an activated complex and then this decomposes to form the products

Question 27

What is the activated complex?

Answer 27

An unstable arrangement of atoms formed at the maximum of the potential energy barrier during a reaction

Question 28

What is a catalyst?

Answer 28

A substance that increases the rate of a reaction but can be recovered unchanged at the end of a reaction

Question 29

What do catalysts provide?

Answer 29

An alternative reaction pathway that has a lower activation energy

Question 30

How do catalysts work?

Answer 30

By reducing the activation energy the catalyst allows more reactant molecules to have an energy greater than the activation energy so increases rate of reaction

Question 31

What is the difference in activation energy between catalysed and non-catalysed reaction?

Answer 31

Activation energy is lower in catalysed reactions than non-catalysed reactions

Question 32

What is the difference in enthalpy change between catalysed and non-catalysed reactions?

Answer 32

Enthalpy change stays the same

Question 33

What is temperature?

Answer 33

A measure of the average kinetic energy of the particles of a substance

Question 34

What type of diagram can be used to show the energy of particles when measuring temperature?

Answer 34

An energy distribution diagram

Question 35

What does the area under the energy distribution distribution diagram represent?

Answer 35

The number of particles

Question 36

How do you find the number of particles with greater than the activation energy?

Answer 36

The area under the curve beyond Ea

Question 37

Describe the number of particles with greater than the activation energy in hot samples compared to cold

Answer 37

The number of particles with greater than the activation energy in a hot sample is greater than in a cold sample

Question 38

Is the rate of reaction faster in hot or cold samples?

Answer 38

Hot

Question 39

When a catalyst is used is the number of particles with greater than the activation energy more or less?

Answer 39

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