Collision Theory - Rates of Reaction (1.1)

Question 1

What is thermodynamics based on?

Answer 1

Energy changes in a reaction

Is the reaction energetically favourable? - will it be possible?

Question 2

What is kinetics based on?

Answer 2

Speed of a reaction

How quickly do we make products or reach equilibrium?

Question 3

What does the collision theory state?

Answer 3

A reaction between particles will only take place if:

1. The particles collide
2. They collide w/ sufficient energy (activation energy - Ea)
3. Collide with the correct orientation

Question 4

In an energy profile, which section is labelled as the Ea?

Answer 4

From reactants to the peak of the curve

Question 5

What is the x-axis of an energy profile?

Answer 5

Reaction coordinate

Question 6

What is the y-axis of an energy profile?

Answer 6

Enthalpy

Question 7

In an energy profile, which section is labelled as ΔH?

Answer 7

The difference in enthalpy between reactants & products

Question 8

In an energy profile, what is the peak of the curve?

Answer 8

The transition state (energy maximum)

Question 9

In an exothermic reaction, do the reactants have lower/higher enthalpy than products?

Answer 9

In an exothermic reaction, the reactants have a higher enthalpy than the products

Question 10

In an endothermic reaction, do the reactants have lower/higher enthalpy than products?

Answer 10

In an endothermic reaction, reactants have a lower enthalpy than products

Question 11

Name 4 factors that increase the probability of collision

Answer 11

• Increase concentration
• Increase pressure
• Increase surface area
• Stir the solution

Question 12

Give the x-axis of a Maxwell-Boltzmann distribution graph

Answer 12

Energy

Question 13

Give the y-axis of a Maxwell-Boltzmann distribution graph

Answer 13

Number of particles

Question 14

Describe the shape of the Maxwell-Boltzmann distribution graph

Answer 14

Starts from 0 (as 0 particles have some energy) and there is a curve than goes down (like mountain peak) & begins to plateau towards the end (but never reaches 0)

Question 15

Where is the Ea on the Maxwell-Boltzmann distribution graph?

Answer 15

The shaded area near the start of the plateau which represents the particles enough energy to react

Question 16

Name the way to increase the energy of each particle

Answer 16

Increase temperature

Question 17

How does increasing the temperature the reaction affect the rate?

Answer 17

Increases the rate of the reaction as:

• Heating a reaction will give the particles more kinetic energy so they will move faster & collide more frequently
• The greatest effect is increasing the average energy of the particles
• More particles have E>Ea (sufficient energy)

Question 18

How does increasing the temperature affect the Maxwell-Boltzmann distribution graph?

Answer 18

• It shifts the curve to the right
• Flattens the peak (the avg. particle has more energy)
• The plateau is higher (more particles have E>Ea)

Question 19

How do you decrease the amount of energy required for the reaction?

Answer 19

Add a catalyst

Question 20

Give the definition of a catalyst

Answer 20

A substance that can speed up the rate of reaction without being used up itself

Question 21

How does a catalyst increase the rate of reaction?

Answer 21

A catalyst provides an alternative route for the reaction w/ a lower Ea (catalyst does not lower the Ea)

Question 22

How does adding a catalyst affect the energy profile?

Answer 22

It lowers the peak of the curve

Question 23

How does a catalyst affect the Ea on the Maxwell-Boltzmann distribution graph?

Answer 23

The Ea is lower, so the shaded area is increased - more particles have E>Ea