Booklet 6 - Rates Of Reaction

Question 1

What is the rate of a chemical?

Answer 1

Tells you how fast reactants turn into products

Question 2

What two ways can we measure the rate of a chemical reaction?

Answer 2

1) . Measuring how quickly the reactants are used up

2) . Measure how quickly a product is made

Question 3

Whats the equation for the mean rate of a reaction (reactant)?

Answer 3

Quantity of reactant used ➗ time taken

Question 4

Whats the equation for the mean rate of a reaction (product)?

Answer 4

Quantity of product formed ➗ time taken

Question 5

What two descriptions can be made from seeing the rate of a reaction on a graph?

Answer 5

1) . The steeper the line the faster the rate
2) . As reactants are used up the concentration of these reactant particles decreases, there are few available then, so the rate decreases and eventually the gradient becomes zero ie a horizontal line

Question 6

What is the collision theory?

Answer 6

Explains how various factors affect rates of reaction

Question 7

What does the collision theory suggest?

Answer 7

That chemical reactions only occur when reacting particles collide with each other and with sufficient energy

Question 8

What is the minimum amount of energy particles require called?

Answer 8

The minimum amount of energy that particles must have to react is called the activation energy

Question 9

How does temperature affect rate?

Answer 9

Increasing the temperature increases the speed of the reacting particles so that they collide more & more energetically. The activation energy is overcome more often and the rate increases

Question 10

How does concentration affect rate?

Answer 10

Increasing concentration of reactants in solutions or increasing the pressure of reacting gases also increase the frequency of collisions as they’re now closer together, and so increase the rate

Question 11

How does surface area affect rate?

Answer 11

Large pieces of solid have a small area relative to their volume ie their inner surfaces aren’t exposed & are not available to react. Therefore, fewer collisions occur and the reaction is slower

Question 12

How can you increase the SA to increase the rate?

Answer 12

Breaking the solid into smaller pieces increases the S.A to volume ratio, so for the same volume of the solid, the particles around it will have more area to work on, increasing the frequency of collisions and therefore increasing rate.

Question 13

What are catalysts?

Answer 13

Catalysts change the rate of reaction but are not used up during the reaction.
- Different catalysts are required for different reactions

Question 14

How do catalysts affect rate?

Answer 14

They increase the rate of reaction by providing a different pathway for the reaction, that has a lower activation energy

Question 15

What’s a reversible reaction?

Answer 15

In some chemical reactions, the products of the reaction can react to produce the original reactants

Question 16

How is a reversible reaction represented?

Answer 16

A + B -> C + D

Question 17

What two things could a reversible reaction show?

Answer 17

If a reversible reaction is exothermic in one direction, and endothermic in the opposite direction. The same amount of energy is transferred in each case

Question 18

When is equilibrium reached?

Answer 18

When a reversible reaction occurs in a apparatus or closed system, nothing can escape or be added, equilibrium is reached when the forward and reverse reactions occur at exactly the same rate

Question 19

What do the relative amounts of all the reactants and products at equilibrium depend on?

Answer 19

The conditions of the reaction

Question 20

What happens when a change is made to a system that has reached equilibrium?

Answer 20

If a change is made to any of the conditions, then the system responds to counteract the change

Question 21

What idea can we use to predict the effects of changing conditions on system at equilibrium?

Answer 21

Le Chatelie’s Principle

Question 22

What is the effect of changing concentration?

Answer 22

If the concentration of one of the reactants or products is changed, the system is no longer at equilibrium and the concentrations of all the substances will change until equilibrium is reached again

Question 23

What happens if the concentration of reactant is increased?

Answer 23

More products will be formed until equilibrium is reached again

Question 24

What happens if the concentration of reactant is decreased?

Answer 24

More reactants will react until equilibrium is reached again

Question 25

If the temperature of a system at equilibrium is increased what two things happen?

Answer 25

1) . The relative amount of products at equilibrium increases for an endothermic reactions
2) . The relative amount of products at equilibrium decreases for an exothermic reactions

Question 26

If the temperature of a system at equilibrium is decreased what two things could happen?

Answer 26

1) . The relative amount of products at equilibrium decreased for an endothermic reactions
2) . The relative amount of products at equilibrium increases for an exothermic reactions

Question 27

What does an increase in pressure do to the equilibrium?

Answer 27

Causes the equilibrium position to shift towards the side with the smaller number of molecules as shown by the symbol equation for that reaction

Question 28

What does a decrease in pressure do to the equilibrium?

Answer 28

Causes the equilibrium position to shift towards the side with the larger number of molecules as shown by the symbol equation for that reaction