10.1 Reaction rates

Question 1

What is the rate of a chemical reaction?

Answer 1

A measure of how fast a reactant is being used up or how fast a product is being formed

Question 2

Definition of rate of reaction

Answer 2

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

Question 3

What is the equation to calculate rate?

Answer 3

Question 4

When is rate of reaction fastest?

Answer 4

At the start of reaction, as each reactant is at its highest concentration. It slows down as the reaction proceeds because the reactants are being used up and their concentration decreases

Question 5

What are the factors that can change the rate of a chemical reaction?

Answer 5

Concentration (pressure for gases), temperature, use of a catalyst, surface area of solid reactants

Question 6

What is collision theory?

Answer 6

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 a reaction

Question 7

Why are some collisions effective and some ineffective?

Answer 7

-The particles must collide with the correct orientation
-The particles must have sufficient energy to overcome the activation energy barrier of a reaction

Question 8

How does increasing the concentration affect the rate of reaction?

Answer 8

When concentration of a reactant is increase, the rate of reaction increases. This is because an increase in concentration increases the number of particles in the same volume, the particles are closer together and collide more frequently, so there will be more effective collisions and an increased rate of reaction

Question 9

How does increasing the pressure affect the rate of reaction?

Answer 9

When the pressure of a gas increases, the rate of reaction increases. The concentration of the gas molecules increases as the same number of gas molecules occupy the same volume. The gas molecules are closer together and collide more frequently, leading to more effective collisions in the same time

Question 10

How can the progress of a chemical reaction be followed?

Answer 10

-Monitoring the removal (decrease in concentration) of a reactant
-Following the formation (increase in concentration) of a product

Question 11

If a reaction produces a gas how can you determine the rate of reaction?

Answer 11

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

Question 12

How do you measure rate of reaction from a graph?

Answer 12

Tangent is join at the point you want to measure (eg. t=0 for initial rate of reaction). The gradient of the tangent gibes the rate of reaction

Question 13

What is the apparatus used to measure the rate of a reaction in which a gas is produced?

Answer 13

or a gas syringe

Question 14

What are the steps for finding the rate of reaction for the decomposition of hydrogen peroxide

Answer 14

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, a stop clock is started
4. The volume of gas produced in the measuring cylinder is recorded at regular intervals until the reaction is complete
5. Reaction is complete when no more gas is produced
6. Graph plotted of total volume of gas produced against time