# data[].attributes.body
Reversible Reactions

# data[].attributes.attachment_link.readable_text
In some chemical reactions, the of the reaction can react together to produce the original . These reactions are called . They can be represented in the following way:

The symbol ⇌ has two half arrowheads, one pointing in each direction. It is used in equations that show reversible reactions:

the forward reaction is the one that goes to the right

the backward reaction is the one that goes to the left

The reaction mixture may contain reactants and products, and their proportions may be changed by altering the reaction conditions.

Ammonium chloride

Ammonium chloride is a white solid. It breaks down when heated, forming ammonia and hydrogen chloride. When these two gases are cool enough, they react together to form ammonium chloride again.

This reversible reaction can be modelled as:

ammonium chloride ⇌ ammonia + hydrogen chloride

Energy changes in reversible reactions

If a reaction is in one direction, it will be in the other direction. The same amount of energy is transferred in both the forwards and reverse reaction.

Copper sulfate

Blue copper sulfate is described as . The copper in its structure are surrounded by water . This water is driven off when blue hydrated copper sulfate is heated, leaving white copper sulfate. This reaction is reversible:

hydrated copper sulfate ⇌ anhydrous copper sulfate + water

The forward reaction is endothermic and the reverse reaction is exothermic.

Dynamic equilibrium

When a reversible reaction happens in a closed container, it reaches a dynamic . At equilibrium:

the forward and backward reactions are still happening

the forward and backward reactions have the same rate of reaction

the of all the reacting substances remain constant

# data[].attributes.attachment_link.title
Reversible reactions - Reversible reactions - AQA - GCSE Chemistry (Single Science) Revision - AQA - BBC Bitesize

# data[].attributes.attachment_link.description
In some chemical reactions, the of the reaction can react together to produce the original . These reactions are called . They can be represented in the following way: The symbol ⇌ has two half arrowheads, one pointing in each direction.

# data[].attributes.body
Sample Exam Questions

# data[].attributes.attachment_link.readable_text
Multiple choice questions appear throughout both exam papers, and at both foundation tier and higher tier. Multiple choice questions are usually asked as questions, often starting with 'what is...' or 'why...'.

You have three or four options to choose from in a multiple choice question. You must choose the number of options asked for in the question by placing ticks in boxes. Most multiple choice questions require just one tick, but a few ask for two ticks. You will not get a mark if you leave all the boxes blank, or if you put a tick in more than the required number of boxes.

Multiple choice questions often have two answers that could, at first glance, be correct. It is important to check all the answers before deciding which box to tick. It is also important to check that your chosen statement answers the question - some questions might include an option that is a correct statement, but that does not answer the question.

Sample question 1 - Foundation

The diagram shows a gas syringe during an investigation to measure the rate of a chemical reaction.

What is the volume of the gas in the syringe?
This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

Sample question 2 - Foundation

The diagram shows the apparatus that a student used to investigate the reaction between marble chips and hydrochloric acid.
This question is AQA material which is reproduced by permission of AQA.

Sample question 4 - Higher

What is the surface area to volume ratio of a cube which has a length of 1 mm?
This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

# data[].attributes.attachment_link.title
Multiple choice questions - Sample exam questions - AQA - GCSE Chemistry (Single Science) Revision - AQA - BBC Bitesize

# data[].attributes.attachment_link.description
Multiple choice questions appear throughout both exam papers, and at both foundation tier and higher tier. Multiple choice questions are usually asked as questions, often starting with 'what is...' or 'why...'. You have three or four options to choose from in a multiple choice question.

# data[].attributes.body
Reversible Reactions

# data[].attributes.attachment_link.readable_text
In some chemical reactions, the of the reaction can react together to produce the original . These reactions are called . They can be represented in the following way:

The symbol ⇌ has two half arrowheads, one pointing in each direction. It is used in equations that show reversible reactions:

the forward reaction is the one that goes to the right

the backward reaction is the one that goes to the left

The reaction mixture may contain reactants and products, and their proportions may be changed by altering the reaction conditions.

Ammonium chloride

Ammonium chloride is a white solid. It breaks down when heated, forming ammonia and hydrogen chloride. When these two gases are cool enough, they react together to form ammonium chloride again.

This reversible reaction can be modelled as:

ammonium chloride ⇌ ammonia + hydrogen chloride

Energy changes in reversible reactions

If a reaction is in one direction, it will be in the other direction. The same amount of energy is transferred in both the forwards and reverse reaction.

Copper sulfate

Blue copper sulfate is described as . The copper in its structure are surrounded by water . This water is driven off when blue hydrated copper sulfate is heated, leaving white copper sulfate. This reaction is reversible:

hydrated copper sulfate ⇌ anhydrous copper sulfate + water

The forward reaction is endothermic and the reverse reaction is exothermic.

Dynamic equilibrium

When a reversible reaction happens in a closed container, it reaches a dynamic . At equilibrium:

the forward and backward reactions are still happening

the forward and backward reactions have the same rate of reaction

the of all the reacting substances remain constant

# data[].attributes.attachment_link.title
Reversible reactions - Reversible reactions - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

# data[].attributes.attachment_link.description
In some chemical reactions, the of the reaction can react together to produce the original . These reactions are called . They can be represented in the following way: The symbol ⇌ has two half arrowheads, one pointing in each direction.

# data[].attributes.body
Sample Exam Questions

# data[].attributes.attachment_link.readable_text
Multiple choice questions appear throughout both exam papers, and at both foundation tier and higher tier. Multiple choice questions are usually asked as questions, often starting with 'what is...' or 'why...'.

You have three or four options to choose from in a multiple choice question. You must choose the number of options asked for in the question by placing ticks in boxes. Most multiple choice questions require just one tick, but a few ask for two ticks. You will not get a mark if you leave all the boxes blank, or if you put a tick in more than the required number of boxes.

Multiple choice questions often have two answers that could, at first glance, be correct. It is important to check all the answers before deciding which box to tick. It is also important to check that your chosen statement answers the question - some questions might include an option that is a correct statement, but that does not answer the question.

Sample question 1 - Foundation

The diagram shows a gas syringe during an investigation to measure the rate of a chemical reaction.

What is the volume of the gas in the syringe?
This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

Sample question 2 - Foundation

The diagram shows the apparatus that a student used to investigate the reaction between marble chips and hydrochloric acid.
This question is AQA material which is reproduced by permission of AQA.

Sample question 4 - Higher

What is the surface area to volume ratio of a cube which has a length of 1 mm?
This question has been written by a Bitesize consultant as a suggestion to the type of question that may appear in an exam paper.

# data[].attributes.attachment_link.title
The rate and extent of chemical change - Multiple choice questions - Sample exam questions - The rate and extent of chemical change - AQA - GCSE Combined Science Revision - AQA Trilogy - BBC Bitesize

# data[].attributes.attachment_link.description
Multiple choice questions appear throughout both exam papers, and at both foundation tier and higher tier. Multiple choice questions are usually asked as questions, often starting with 'what is...' or 'why...'. You have three or four options to choose from in a multiple choice question.