Chapter 10.1 - Reaction rates and equilibrium

Question 1

Define the rate of reaction

Answer 1

The change in concentration of a reactant or a product in a given time

Question 2

What is the equation used to calculate the rate of reaction?

Answer 2

rate = change in concentration / time
unit = mol dm⁻³ s⁻¹

Question 3

Why is the rate of a reaction the fastest at the start of the reaction?

Answer 3

Each reactant is at its highest concentration

Question 4

Why does the rate of reaction slow down as the reaction proceeds?

Answer 4

The reactants are being used up and their concentrations decrease

Question 5

What happens once one of the reactants has been completely used up?

Answer 5

The concentration stops changing and the rate of reaction is zero

Question 6

What are the four factors that affect the rate of a chemical reaction?

Answer 6

1. Concentration or pressure when reactants are gases
2. Temperature
3. Use of a catalyst
4. Surface area of solid reactants

Question 7

What is meant by the collision theory?

Answer 7

Two reacting particles must collide for a reaction to occur, and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction

Question 8

How does increasing the concentration affect the rate of reaction?

Answer 8

• An increase in concentration increases the number of particles in the same volume
• The particles are closer together and collide more frequently
• In a given period, there will be more effective collisions(correct orientation and sufficient energy) and an increased rate of reaction

Question 9

How does increasing the pressure of a gas affect the rate of reaction?

Answer 9

• The concentration of the gas molecules increases as the same number of gas molecules occupy a smaller volume due to the increased pressure
• The gas molecules are closer together and collide more frequently, leading to more effective collisions in the same time

Question 10

What are the two methods for following the progress of a reaction?

Answer 10

1. Monitoring the removal of reactant (decrease conc)
2. Following the formation of a product (increase conc)

Question 11

What are the two methods for determining the rate of reaction of gases?

Answer 11

1. Monitoring the volume of gas produced at regular time intervals using gas collection
2. Monitoring the loss of mass of reactants using a balance

Question 12

How would you calculate the rate of reaction with a graph of volume produced against time?

Answer 12

The gradient, change in y / change in x

Question 12

Describe the process on measuring the rate of the decomposition of hydrogen peroxide

Answer 12

1. Hydrogen peroxide is added to the conical flask and the bung is replaced
2. The initial volume of gas in the measuring cylinder is recorded
3. Manganese dioxide catalyst is then quickly added to the conical flask and the bung is replaced
4. A stop clock is started
5. The volumes of gas produced in the measuring cylinder is recorded at regular intervals until the reaction is complete
6. The reaction is complete when no more gas is produced