Reaction Rates

Question 1

What is the activation energy?

Answer 1

The minimum energy required for the reaction to occur

Question 2

Collision theory states that a reaction will not take place between two particles unless they…

Answer 2

• Collide in the correct orientation
• Collide with at least a certain minimum amount of kinetic energy

Question 3

What is rate of reaction?

Answer 3

Change in concentration divided by time

Question 4

What 4 factors can increase the frequency of collisions between particles?

Answer 4

Concentration, pressure, surface area, temperature

Question 5

What effect does increasing concentration of reagents in a solution have on the reaction rate?

Answer 5

Increases the number of reactant particles in a given volume, and so increases the frequency of collisions between molecules, therefore more frequent successful collisions

Question 6

What effect does increasing pressure have on the reaction rate?

Answer 6

More particles in a given volume, therefore more frequent successful collisions

Question 7

What effect does increasing the surface area of solid particles have on the reaction rate?

Answer 7

Increases the number of reactant particles available for collision, and so increases the frequency of successful collisions

Question 8

What effect does increasing the temperature have on the reaction rate?

Answer 8

Always increases the rate of reaction. Particles have more energy at a higher temperature. This leads to more particles with energy greater than the activation energy therefore more frequent successful collisions

Question 9

What are three ways you can measure reaction rates?

Answer 9

1. Collection of gas from a reaction using a gas syringe
2. Collection of gas from a reaction using a measuring cylinder
3. Mass of reaction recorded to record mass lost over a time period

Question 10

What are five important points about the Maxwell-Boltzmann Distribution Curve?

Answer 10

1. There are no particles with zero energy: graph starts at the origin
2. The curve does not touch the x-axis at higher energy, because there will always be some molecules with very high energies
3. The area under the curve is equal to the total number of molecules in the system
4. It is labelled energy on the x-axis and number of molecules on the y-axis
5. The peak of the curve indicates the most probable energy

Question 11

What is a catalyst?

Answer 11

A substance that increases the rate of reaction but itself is unchanged at the end of a reaction

Question 12

How does a catalyst work?

Answer 12

Providing an alternative route which has a lower activation energy

Question 13

Give and explain the two types of catalysts

Answer 13

Heterogeneous catalysts - Catalysts which are in a different phase to the reactants
Homogeneous catalysts - Catalysts which are in the same phase as the reactants

Question 14

Why is use of catalysts in industrial processes beneficial to the environment?

Answer 14

Lower the energy demand for a reaction, can be done at lower temperatures and results in reduces CO2 emissions due to less fossil fuels being burned