10.1 Reaction rates

Question 1

What is the rate of reaction?

Answer 1

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

Question 2

What is the equation for rate of reaction?

Answer 2

change in concentration / time

Question 3

What is the units for rate?

Answer 3

mol dm-3 s-1

Question 4

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

Answer 4

Each reactant is at its highest concentration.

Question 5

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

Answer 5

The reactants are being used up and their concentrations decrease.

Question 6

What happens to the rate of reaction when one of the reactants is used up in the reaction?

Answer 6

The rate of reaction is zero.

Question 7

What is collision theory?

Answer 7

It states that two reacting particles must collide for a reaction to occur

Question 8

What conditions make a collision effective?

Answer 8

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

Question 9

How does increasing the concentration affect the rate of reaction?

Answer 9

An increase in concentration means there is an increase in the number of particles in the same volume.
Particles are closer together so collide more frequently.
Therefore there will be more effective collisions and so an increased rate of reaction.

Question 10

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

Answer 10

When a gas is compressed into a smaller volume the pressure of gas is increased and the rate of reaction increases.
The concentration of the gas molecules increases as there is the same number of gas molecules occupy a smaller volume.
The gas molecules are closer together and so collide more frequently, leading to more effective collisions at the same time.