A salt is a compound formed when the hydrogen in an acid is replaced by a metal ion. For example, replacing H in HCl with sodium gives sodium chloride (NaCl).

In preparing a soluble salt using an insoluble base, the base is added in ______ to ensure all the acid has reacted. The excess base is then removed by ______ .

In preparing a soluble salt using an insoluble base, the base is added in excess to ensure all the acid has reacted. The excess base is then removed by filtration .

Why is the salt solution heated when preparing a soluble salt using an insoluble base?

The solution is heated to evaporate water and produce a saturated solution, from which the salt crystallises on cooling. Saturation is tested by dipping a cold glass rod into the solution and checking whether crystals form on it.

When preparing a soluble salt by acid-alkali titration, the titration is first carried out ______ an indicator. The experiment is then repeated using the same volumes ______ an indicator.

When preparing a soluble salt by acid-alkali titration, the titration is first carried out with an indicator. The experiment is then repeated using the same volumes without an indicator.

True or False? When preparing a soluble salt using the titration method, the indicator should be left in the final solution.

False. The indicator must be omitted from the final mixture because it would contaminate the salt crystals. The exact volumes needed are determined in a first titration run that uses the indicator.

When copper(II) oxide reacts with dilute sulfuric acid, the salt ______ (CuSO 4 ) is formed along with ______ .

When copper(II) oxide reacts with dilute sulfuric acid, the salt copper(II) sulfate (CuSO 4 ) is formed along with water .

What is a precipitation reaction ?

A precipitation reaction is one in which two soluble reactants are mixed and an insoluble product (the precipitate) forms. It is used to prepare insoluble salts.

To prepare an insoluble salt, two soluble salts are dissolved in water and ______ together. The insoluble salt forms as a ______ which is then collected by filtration.

To prepare an insoluble salt, two soluble salts are dissolved in water and mixed together. The insoluble salt forms as a precipitate which is then collected by filtration.

What is the purpose of washing the precipitate with distilled water during the preparation of an insoluble salt?

Washing with distilled water removes traces of the other soluble salts that were present in the reaction mixture, giving a purer product.

In the preparation of lead(II) sulfate, lead(II) nitrate is mixed with potassium sulfate solution. The lead(II) sulfate forms as an insoluble ______ which is separated by ______ .

In the preparation of lead(II) sulfate, lead(II) nitrate is mixed with potassium sulfate solution. The lead(II) sulfate forms as an insoluble precipitate which is separated by filtration .

True or False? An insoluble salt can be prepared by adding an insoluble reactant to an acid.

False. Insoluble salts are prepared by precipitation: mixing two soluble solutions to form the insoluble salt. The insoluble solid is then filtered off.

Which families of salts are always soluble, with no exceptions?

All nitrates are soluble. All sodium , potassium and ammonium salts are also soluble. Neither rule has any exceptions.

Chlorides are soluble, except those of ______ and ______ , which are insoluble.

Chlorides are soluble, except those of lead and silver , which are insoluble.

Which common sulfates are insoluble?

Barium sulfate, lead(II) sulfate and calcium sulfate are insoluble. All other common sulfates are soluble.

Carbonates are generally insoluble, except the carbonates of ______ , ______ , and ______ , which are soluble.

Carbonates are generally insoluble, except the carbonates of sodium , potassium and ammonium , which are soluble.

True or False? All hydroxides are insoluble.

False. Sodium, potassium and ammonium hydroxides are soluble. Calcium hydroxide is only partially soluble. All other common hydroxides are insoluble.

To decide whether to prepare a salt by precipitation, first determine whether the salt is ______ . If it is, precipitation is the correct method: mix two ______ solutions to form it.

To decide whether to prepare a salt by precipitation, first determine whether the salt is insoluble . If it is, precipitation is the correct method: mix two soluble solutions to form it.

What is a hydrated salt ?

A hydrated salt is a salt that contains water molecules within its crystal structure. The water, called water of crystallisation, affects the salt's colour and shape.

Hydrated copper(II) sulfate (CuSO 4 ·5H 2 O) is ______ in colour. When heated, it loses water of crystallisation to form ______ copper(II) sulfate, which is white.

Hydrated copper(II) sulfate (CuSO 4 ·5H 2 O) is blue in colour. When heated, it loses water of crystallisation to form anhydrous copper(II) sulfate, which is white.

What is water of crystallisation ?

Water of crystallisation is water incorporated into the crystal structure of a salt during crystallisation. It is shown in the formula by a dot, e.g. CuSO 4 ·5H 2 O contains 5 moles of water per mole of salt.

Why does anhydrous copper(II) sulfate (CuSO 4 ) turn blue when water is added?

Adding water converts the anhydrous salt to its hydrated form (CuSO 4 ·5H 2 O), which is blue. This reaction is reversible: heating the hydrated salt drives off the water and regenerates the white anhydrous form.

In the formula for a hydrated salt, water of crystallisation is separated from the main formula by a ______ . For example, CoCl 2 ·6H 2 O shows there are ______ moles of water per mole of cobalt(II) chloride.

In the formula for a hydrated salt, water of crystallisation is separated from the main formula by a dot . For example, CoCl 2 ·6H 2 O shows there are 6 moles of water per mole of cobalt(II) chloride.

True or False? Heating hydrated copper(II) sulfate and then adding water returns it to its original blue form.

True. The dehydration of hydrated copper(II) sulfate is a reversible reaction: CuSO 4 ·5H 2 O ⇌ CuSO 4 + 5H 2 O. Heating drives the forward reaction. Adding water reverses it.

O LevelChemistryCambridge (CIE)Flashcards7. Acids, Bases & Salts7.3 Preparation of Salts

7.3 Preparation of Salts (Cambridge (CIE) O Level Chemistry): Flashcards

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FrontPreparing Soluble Salts
What is a salt?

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Cards in this collection (23)

What is a salt?
A salt is a compound formed when the hydrogen in an acid is replaced by a metal ion. For example, replacing H in HCl with sodium gives sodium chloride (NaCl).
In preparing a soluble salt using an insoluble base, the base is added in ______ to ensure all the acid has reacted. The excess base is then removed by ______.
In preparing a soluble salt using an insoluble base, the base is added in excess to ensure all the acid has reacted. The excess base is then removed by filtration.
Why is the salt solution heated when preparing a soluble salt using an insoluble base?
The solution is heated to evaporate water and produce a saturated solution, from which the salt crystallises on cooling. Saturation is tested by dipping a cold glass rod into the solution and checking whether crystals form on it.
When preparing a soluble salt by acid-alkali titration, the titration is first carried out ______ an indicator. The experiment is then repeated using the same volumes ______ an indicator.
When preparing a soluble salt by acid-alkali titration, the titration is first carried out with an indicator. The experiment is then repeated using the same volumes without an indicator.
True or False?
When preparing a soluble salt using the titration method, the indicator should be left in the final solution.
False.
The indicator must be omitted from the final mixture because it would contaminate the salt crystals. The exact volumes needed are determined in a first titration run that uses the indicator.
When copper(II) oxide reacts with dilute sulfuric acid, the salt ______ (CuSO₄) is formed along with ______.
When copper(II) oxide reacts with dilute sulfuric acid, the salt copper(II) sulfate (CuSO₄) is formed along with water.
What is a precipitation reaction?
A precipitation reaction is one in which two soluble reactants are mixed and an insoluble product (the precipitate) forms. It is used to prepare insoluble salts.
To prepare an insoluble salt, two soluble salts are dissolved in water and ______ together. The insoluble salt forms as a ______ which is then collected by filtration.
To prepare an insoluble salt, two soluble salts are dissolved in water and mixed together. The insoluble salt forms as a precipitate which is then collected by filtration.
What is the purpose of washing the precipitate with distilled water during the preparation of an insoluble salt?
Washing with distilled water removes traces of the other soluble salts that were present in the reaction mixture, giving a purer product.
In the preparation of lead(II) sulfate, lead(II) nitrate is mixed with potassium sulfate solution. The lead(II) sulfate forms as an insoluble ______ which is separated by ______.
In the preparation of lead(II) sulfate, lead(II) nitrate is mixed with potassium sulfate solution. The lead(II) sulfate forms as an insoluble precipitate which is separated by filtration.
True or False?
An insoluble salt can be prepared by adding an insoluble reactant to an acid.
False.
Insoluble salts are prepared by precipitation: mixing two soluble solutions to form the insoluble salt. The insoluble solid is then filtered off.
Which families of salts are always soluble, with no exceptions?
All nitrates are soluble.
All sodium, potassium and ammonium salts are also soluble.
Neither rule has any exceptions.
Chlorides are soluble, except those of ______ and ______, which are insoluble.
Chlorides are soluble, except those of lead and silver, which are insoluble.
Which common sulfates are insoluble?
Barium sulfate, lead(II) sulfate and calcium sulfate are insoluble. All other common sulfates are soluble.
Carbonates are generally insoluble, except the carbonates of ______, ______, and ______, which are soluble.
Carbonates are generally insoluble, except the carbonates of sodium, potassium and ammonium, which are soluble.
True or False?
All hydroxides are insoluble.
False.
Sodium, potassium and ammonium hydroxides are soluble. Calcium hydroxide is only partially soluble. All other common hydroxides are insoluble.
To decide whether to prepare a salt by precipitation, first determine whether the salt is ______. If it is, precipitation is the correct method: mix two ______ solutions to form it.
To decide whether to prepare a salt by precipitation, first determine whether the salt is insoluble. If it is, precipitation is the correct method: mix two soluble solutions to form it.
What is a hydrated salt?
A hydrated salt is a salt that contains water molecules within its crystal structure. The water, called water of crystallisation, affects the salt's colour and shape.
Hydrated copper(II) sulfate (CuSO₄·5H₂O) is ______ in colour. When heated, it loses water of crystallisation to form ______ copper(II) sulfate, which is white.
Hydrated copper(II) sulfate (CuSO₄·5H₂O) is blue in colour. When heated, it loses water of crystallisation to form anhydrous copper(II) sulfate, which is white.
What is water of crystallisation?
Water of crystallisation is water incorporated into the crystal structure of a salt during crystallisation. It is shown in the formula by a dot, e.g. CuSO₄·5H₂O contains 5 moles of water per mole of salt.
Why does anhydrous copper(II) sulfate (CuSO₄) turn blue when water is added?
Adding water converts the anhydrous salt to its hydrated form (CuSO₄·5H₂O), which is blue. This reaction is reversible: heating the hydrated salt drives off the water and regenerates the white anhydrous form.
In the formula for a hydrated salt, water of crystallisation is separated from the main formula by a ______. For example, CoCl₂·6H₂O shows there are ______ moles of water per mole of cobalt(II) chloride.
In the formula for a hydrated salt, water of crystallisation is separated from the main formula by a dot. For example, CoCl₂·6H₂O shows there are 6 moles of water per mole of cobalt(II) chloride.
True or False?
Heating hydrated copper(II) sulfate and then adding water returns it to its original blue form.
True.
The dehydration of hydrated copper(II) sulfate is a reversible reaction: CuSO₄·5H₂O ⇌ CuSO₄ + 5H₂O. Heating drives the forward reaction. Adding water reverses it.

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