C7.3 - Reaction profiles

Question 1

You can find out more about what is happening in a particular reaction by what?

Answer 1

You can find out more about what is happening in a particular reaction by looking at its reaction profile

Question 2

Reaction profiles are diagrams that show what?

Answer 2

Reaction profiles are diagrams that show the relative amounts of energy contained in the:

1. Reactants
2. Products

Question 3

Reaction profiles are diagrams that show the relative amounts of energy contained in the reactants and the products, measured in kilojoules per mole (kJ/mol).
A curved line, drawn from reactants to products, shows what?

Answer 3

A curved line, drawn from reactants to products, shows the course of the reaction

Question 4

Reaction profiles are diagrams that show the relative amounts of energy contained in the reactants and the products, measured in kilojoules per mole (kJ/mol).
A curved line, drawn from reactants to products, shows the course of the reaction.
What does the difference in energy between the reactants and the peak of the curve indicate?

Answer 4

The difference in energy between the:
1. Reactants
2. Peak of the curve
indicates the energy input required for the reaction to take place, the activation energy

Question 5

In the reaction profile for an exothermic reaction, where are the products?

Answer 5

In the reaction profile for an exothermic reaction, the products are at a lower energy level than the reactants

Question 6

In the reaction profile for an exothermic reaction, the products are at a lower energy level than the reactants.
What does this mean?

Answer 6

This means that when the reactants form the products, energy is transferred to the surroundings

Question 7

What is the difference between the energy levels of the reactants and the products?

Answer 7

The difference between the energy levels of the:
1. Reactants
2. Products
is the energy change during the reaction

Question 8

The difference between the energy levels of the reactants and the products is the energy change during the reaction, measured in kJ/mol.
What happens to an amount of energy equal to the difference in energy between the products and the reactants?

Answer 8

An amount of energy equal to the difference in energy between the:
1. Products
2. Reactants
is transferred to the surroundings

Question 9

The difference between the energy levels of the reactants and the products is the energy change during the reaction, measured in kJ/mol.
An amount of energy equal to the difference in energy between the products and the reactants is transferred to the surroundings.
Therefore, what happens in an exothermic reaction?

Answer 9

In an exothermic reaction, the surroundings:

1. Get hotter
2. Their temperature rises

Question 10

In the reaction profile for an endothermic reaction, where are the products?

Answer 10

In the reaction profile for an endothermic reaction, the products are at a higher energy level than the reactants

Question 11

In the reaction profile for an endothermic reaction, the products are at a higher energy level than the reactants.
What happens as the reactants react to form products?

Answer 11

As the reactants react to form products, energy is transferred from the surroundings to the reaction mixture

Question 12

In the reaction profile for an endothermic reaction, the products are at a higher energy level than the reactants.
As the reactants react to form products, energy is transferred from the surroundings to the reaction mixture.
What happens?

Answer 12

The:

1. Surroundings get colder
2. Temperature of the surroundings decreases

Question 13

What is there before colliding particles of reactants have sufficient energy to cause a reaction?

Answer 13

There is a minimum amount of energy needed before colliding particles of reactants have sufficient energy to cause a reaction

Question 14

There is a minimum amount of energy needed before colliding particles of reactants have sufficient energy to cause a reaction.
What is this energy needed to start a reaction called?

Answer 14

This energy needed to start a reaction is called the activation energy

Question 15

Activation energy

Answer 15

Activation energy is the minimum amount of energy needed for a reaction to take place

Question 16

Activation energy is shown on what?

Answer 16

Activation energy is shown on reaction profiles

Question 17

There is a minimum amount of energy needed before colliding particles of reactants have sufficient energy to cause a reaction.
What happens if colliding particles of reactants collide with less energy than the activation energy?

Answer 17

If colliding particles of reactants collide with less energy than the activation energy, they will just bounce off each other

Question 18

What happens as a chemical reaction takes place?

Answer 18

As a chemical reaction takes place:

1. First, the chemical bonds between the atoms or ions in the reactants are broken
2. Then new chemical bonds are formed to make the products

Question 19

What has to be supplied to break chemical bonds?

Answer 19

Energy has to be supplied to break chemical bonds

Question 20

Energy has to be supplied to break chemical bonds.

What does this mean?

Answer 20

This means that bond breaking is an endothermic process

Question 21

What happens when new bonds are formed?

Answer 21

When new bonds are formed, energy is transferred to the surroundings

Question 22

Hydrogen and oxygen react to make what?

Answer 22

1. Hydrogen
2. Oxygen
   react to make water

Question 23

Hydrogen and oxygen react to make water.

What has to be happen, so that bonds between oxygen atoms and hydrogen atoms in water can be formed?

Answer 23

So that bonds between oxygen atoms and hydrogen atoms in water can be formed, the bonds between:
1. Hydrogen atoms
2. Oxygen atoms
have to be broken

Question 24

In reality, what do the 2 processes of bond breaking and bond making do?

Answer 24

In reality, the 2 processes of bond breaking and bond making do not happen in sequence

Question 25

In reality, the 2 processes of bond breaking and bond making do not happen in sequence
All the bonds do not break and then all the new bonds form.
The bond breaking and making processes happen at the same time.
However, comparing the energy required to break the bonds with the energy released when the new bonds form gives what?

Answer 25

Comparing the energy required to break the bonds with the energy released when the new bonds form gives a good guide to the overall energy change

Question 26

Comparing the energy required to break the bonds with the energy released when the new bonds form gives a good guide to the overall energy change.
What does this allow you to do?

Answer 26

This allows you to decide if a reaction will be:
1. Exothermic
Or,
2. Endothermic

Question 27

BB

RR

Answer 27

Breaking bonds aBsorbs energy

FoRming bonds Releases energy

Question 28

Reaction profiles are diagrams that show the relative amounts of energy contained in the reactants and the products, measured in what?

Answer 28

Reaction profiles are diagrams that show the relative amounts of energy contained in the:
1. Reactants
2. Products
,measured in kilojoules per mole (kJ/mol)

Question 29

The difference between the energy levels of the reactants and the products is the energy change during the reaction, measured in what?

Answer 29

The difference between the energy levels of the:
1. Reactants
2. Products
is the energy change during the reaction, measured in kJ/mol

Question 30

In the reaction profile for an endothermic reaction, the products are at a higher energy level than the reactants.
As the reactants react to form products, energy is transferred from the surroundings to the reaction mixture.
The surroundings get colder and the temperature of the surroundings decreases, because what?

Answer 30

The:
1. Surroundings get colder
2. Temperature of the surroundings decreases
,because energy is taken in during the reaction

Question 31

Energy has to be supplied to break chemical bonds.

This means that breaking bonds is an endothermic process, because what?

Answer 31

This means that breaking bonds is an endothermic process, because energy is taken in from the surroundings

Question 32

When new bonds are formed, energy is transferred to the surroundings, so what?

Answer 32

When new bonds are formed, energy is transferred to the surroundings, so bond making is an exothermic process

Question 33

In reality, the 2 processes of bond breaking and bond making do not happen in sequence.
All the bonds do not what and then all the new bonds do what?

Answer 33

1. All the bonds do not break

2. Then all the new bonds form

Question 34

In reality, the 2 processes of bond breaking and bond making do not happen in sequence.
All the bonds do not break and then all the new bonds form.
The bond breaking and bond making processes happen at what?

Answer 34

The bond:
1. Breaking
2. Making
processes happen at the same time