M3 - Rates of reaction

Question 1

What 2 parts make up collision theory?

Answer 1

1.Particles must collide with sufficient energy
2. They must collide with the correct orientation

Particles must collide in correct orientation

Question 2

How does a homogeneous catalyst interact with the reactants?

Answer 2

Forms an intermediate

This intermediate breaks down to give the product and regenerates the catalyst

Question 3

Which factors can change the rate of a chemical reaction?

Answer 3

Concentration
Temperature
Use of a catalyst
Surface area of solid reactants

Question 4

Define rate of reaction

Answer 4

The change in concentration of a reactant or a product per unit time OR
Rate = Concentration of reactant (or product) / Time

Question 5

What are the main features of Boltzmann distribution?

Answer 5

No molecules have zero energy
Area under the curve is equal to the number of molecules
No maximum energy

Question 6

What is a homogeneous catalyst?

Answer 6

Has the same physical state as the reactants.

Question 7

What is a heterogeneous catalyst?

Answer 7

Catalysis of a reaction in which the catalyst has a different physical state from the reactants (1)

Question 8

What is the rule of thumb for reaction rate and increasing temperature?

Answer 8

A 10C increase in temperature doubles the rate.

Question 9

What are the two methods of determining reaction rate, when a gas is produced?

Answer 9

Monitoring the volume of gas produced

Monitoring the loss of mass of reactants

Question 10

What does a catalyst do?

Answer 10

A substance that changes the rate of a chemical reaction by providing an alternative ath with a lower activation energy without undergoing any permanent change itself.

Question 11

How does a Boltzmann distribution show the effect of a catalyst?

Answer 11

Activation energy with a catalyst is lower than normal activation energy.
Therefore a greater proportion of molecules exceed the new lower activation energy.

Question 12

Explain why increasing concentration/pressure has its effect on reaction rate

Answer 12

Concentration increases
More particles per unit volume
More frequent collisions
More successful collisions
Rate increases

Question 13

What is a heterogeneous catalyst?

Answer 13

Has a different physical state from the reactants.

Question 14

How does a heterogeneous catalyst interact with the reactants?

Answer 14

Usually solids in contact with gaseous reactants or reactants in solution.
Reactants are adsorbed onto the surface, where the reaction takes place.
After the reaction, the products leave the surface by desorption.

Question 15

Answer 15

A

Question 16

What effect does increasing concentration/pressure have on reaction rate?

Answer 16

increasing concentration and pressure Reaction rate increases

Question 17

How does a Boltzmann distribution curve change when temperature is increased?

Answer 17

The peak is lower and shifted to the right

A greater proportion of molecules can overcome the activation energy

Question 18

Answer 18

C

Question 19

What effect does increasing temperature have on reaction rate?

Answer 19

Reaction rate increases with greater temprature

Question 20

What are the benefits of using a catalyst?

Answer 20

Lowers activation energy
Less electricity used
Product made faster and cuts costs and increases profit
Less fossil fuels used cuts emissions of carbon dioxide

Question 21

Explain why increasing temperature has its effect on reaction rate

Answer 21

with higher temperature
Particles have more energy
Higher speed
Collide more frequently
More successful collisions
Rate increases

Question 22

What are the units of rate of reaction?

Answer 22

mol dm-3s-1 or cm3s-1 or gs-1

Question 23

Give two examples of homogeneous catalysts

Answer 23

Sulphuric acid in the production of esters

Chlorine radicals in ozone depletion

Question 24

What is a homogeneous catalyst?

Answer 24

Catalysis of a reaction in which the catalyst and the reactants are in the same physical state (1)

Question 25

What are the main properties of a catalyst?

Answer 25

Not used up in the reaction.
May react with a reactant to form an intermediate or provide a surface for the reaction to take place.
The catalyst is regenerated at the end of the reaction.

Question 26

Give examples of heterogeneous catalysts

Answer 26

Iron in making ammonia
Platinum or rhodium in reforming
Nickel in hydrogenation of alkenes
Vanadium oxide in making sulphur trioxide

Question 27

Answer 27

D

Question 28

How can progress of a chemical reaction be followed?

Answer 28

Monitoring the removal of a reactant.

Following the formation of a product.