Reaction Rates and Equillibrium

Question 1

What is collision theory?

Answer 1

For particles to react with each other, they must collide.

Question 2

What is the rate of reaction?

Answer 2

The change of concentration / amount of a reactant / product per unit time.

Question 3

What must happen in order for a reaction to occur when two particles collide?

Answer 3

The particles must collide in the right direction and must have a minimum amount of kinetic energy.

Question 4

What is activation energy?

Answer 4

The minimum amount of energy required for a reaction to occur.

Question 5

What is a Maxwell Boltzmann distribution diagram?

Answer 5

A diagram that shows the energy in gas particles. Number of particles is on the Y, kinetic energy is on the X.

Question 6

What is the area under a Maxwell Boltzmann distribution diagram?

Answer 6

The total number of molecules.

Question 7

What is at the peak of a Maxwell Boltzmann distribution diagram?

Answer 7

The most likely energy of a particle.

Question 8

How does a higher temperature look on a Maxwell Boltzmann distribution diagram?

Answer 8

The peak is shifted down, the activation energy includes more particles and everything is shifted to the right.

Question 9

What five factors affect rate of reaction?

Answer 9

Temperature
Pressure
Concentration
Catalyst 
Surface Area

Question 10

Why does a higher temperature mean higher collision rates?

Answer 10

Higher temperatures cause particles to move faster causing them to be more likely to collide with each other.

Question 11

How does concentration / pressure affect rate of reaction?

Answer 11

The particles are forced closer together increasing the probability of particles colliding with each other and causing a reaction.

Question 12

How does a catalyst affect rate of reaction?

Answer 12

It increases rate of reaction by providing an alternative pathway that has a lower activation energy. The catalyst is chemically unchanged by the end of the reaction.

Question 13

What is a heterogeneous catalyst?

Answer 13

A catalyst that is in a different state of matter to the reactants. The reactants are usually reacting on the catalyst.

Question 14

What is a homogeneous catalyst?

Answer 14

A catalyst that is in the same physical state of matter to the reactants. They act as an intermediate. This means they get used up in the reaction to form the product but then get regenerated so that they never got used up.

Question 15

How does a catalyst look on a Maxwell Boltzmann distribution diagram?

Answer 15

The activation energy is moved to the left meaning more particles have the energy required to undergo reaction.

Question 16

What are the advantages of catalysts?

Answer 16

They lower the temperature of the reaction and speed up the reaction as well. This means less energy is required for the reaction and less money is spent on it making it better for the environment and more economically viable. It also means less fossil fuels burned which is good for reducing CO₂ emissions.

Question 17

What is a catalytic converter?

Answer 17

A mesh of catalysts in a car exhaust that help clean up car emissions.

Question 18

What could be a way to experimentally measure reaction rates of a precipitate forming?

Answer 18

Have a cross under a beaker and do the reaction in the beaker. Start a timer when the reaction begins and stop the timer when the cross disappears.

Question 19

What could be a way to experimentally measure reaction rates of mass being lost?

Answer 19

Place the beaker on a scale and do the reaction. The mass should decrease as mass is lost. When the reaction is done, stop the time and record the mass.

Question 20

What could be a way to experimentally measure reaction rates of gas being released?

Answer 20

Get a gas syringe and attach the input to the top of a beaker so all escaping gas goes into the syringe. Start the timer when the reaction begins and stop after a specific time. When you stop the timer, measure the amount of gas in the syringe.

Question 21

How do you get the rate of reaction from a graph?

Answer 21

Find the gradient. If it’s curved, find the tangent and then find the gradient.

Question 22

What are reversible reactions?

Answer 22

Reactions that can go forward and backwards.

Question 23

What is dynamic equilibrium?

Answer 23

Where the rate of the forwards reactions is equal to the rate of the backwards reaction in a closed system.

Question 24

What is Le Chatelier’s Principle?

Answer 24

When an external change is acted upon the system, the system tries to counteract that change.

Question 25

When we increase concentration of a chemical to one side of a dynamic equilibrium, what will happen to the other side?

Answer 25

Increasing concentration on one side will cause the system to make more product using that increased concentration. (This only works when both sides of the reaction are in the same state)

Question 26

What happens when we increase pressure in a dynamic equilibrium?

Answer 26

The equilibrium will favour the side with the fewest number of gas particles.

Question 27

What happens when we decrease pressure in a dynamic equilibrium?

Answer 27

The equilibrium will favour the side with the highest number of gas particles.

Question 28

What happens when we try to increase the temperature in a dynamic equilibrium?

Answer 28

The equilibrium will shift to the endothermic direction.

Question 29

What happens when we try to decrease the temperature in a dynamic equilibrium?

Answer 29

The equilibrium will shift to the exothermic direction.

Question 30

What happens when we add a catalyst to an equilibrium?

Answer 30

It increases the speed on both sides and doesn’t affect balance of the equilibrium.

Question 31

How do we calculate the equilibrium constant?

Answer 31

K𝒸 = Products / Reactants

e. g. 2A + B > 2C + D = [C]² x [D] / [A]² x [B]
* Square brackets show the concentration