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

What two factors determine which method is used to prepare a soluble salt?

The method depends on the solubility of the salt and whether the base is soluble (an alkali) or insoluble . Soluble bases require titration; insoluble reactants use the excess solid method.

When preparing a soluble salt using excess insoluble base , the unreacted solid is removed by .......... and the salt is obtained by crystallisation .

When preparing a soluble salt using excess insoluble base , the unreacted solid is removed by filtration and the salt is obtained by crystallisation .

True or False? Titration is used to prepare a soluble salt from a soluble alkali because excess alkali cannot be removed by filtration.

True. Since alkalis are soluble, any excess would remain in the salt solution and could not be filtered off. Titration finds the exact volume of acid needed to neutralise the alkali, so no excess remains.

In a titration to prepare a pure soluble salt, why is the final titration repeated without indicator?

The indicator is omitted in the final titration so that it does not contaminate the pure salt solution. The volume of acid needed is already known from the first titration, so no indicator is required.

To prepare copper(II) sulfate, .......... acid is warmed and excess .......... is added until no more dissolves, then the mixture is filtered.

To prepare copper(II) sulfate, sulfuric acid is warmed and excess copper(II) oxide is added until no more dissolves, then the mixture is filtered.

How is the name of the salt produced in a reaction determined?

The first part of the salt name comes from the metal (or metal oxide/carbonate) and the second part comes from the acid . For example, hydrochloric acid always gives salts ending in chloride .

True or False? When using excess metal to prepare a salt, the excess metal is removed by evaporation.

False. Excess metal is a solid and is removed by filtration . Evaporation is used afterwards to concentrate the salt solution before crystallisation.

Describe how to check that a salt solution is saturated and ready to crystallise.

Dip a cold glass rod into the hot solution. If crystals form on the rod, the solution is saturated and ready to be left to crystallise .

What is a precipitation reaction ? (Extended Tier Only)

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

Why must both reactants be soluble when preparing an insoluble salt by precipitation? (Extended Tier Only)

Both reactants must be soluble so they can mix freely in solution, allowing the ions to collide and react. If either reactant were insoluble, the ions could not come into contact to form the precipitate .

To prepare an insoluble salt, two .......... solutions are mixed, and the precipitate is collected by .......... . (Extended Tier Only)

To prepare an insoluble salt, two soluble solutions are mixed, and the precipitate is collected by filtration .

True or False? After filtering an insoluble salt, it should be washed with distilled water before drying. (Extended Tier Only)

True. Washing with distilled water removes traces of the other soluble salts from the reaction. This ensures the final product is pure.

Write a word equation for the preparation of lead(II) sulfate by precipitation. (Extended Tier Only)

lead(II) nitrate + potassium sulfate → lead(II) sulfate + potassium nitrate Lead(II) sulfate is the insoluble precipitate that forms when these two soluble solutions are mixed.

Steps for preparing an insoluble salt: Mix two .......... aqueous solutions. Filter to collect the precipitate . Wash with .......... water. Dry the solid. (Extended Tier Only)

Steps for preparing an insoluble salt: Mix two soluble aqueous solutions. Filter to collect the precipitate . Wash with distilled water. Dry the solid.

Why is the precipitation method used to prepare insoluble salts rather than the excess solid or titration method? (Extended Tier Only)

The excess solid and titration methods produce salts in solution, which can only be recovered if the salt is soluble . An insoluble salt would simply settle out as a solid, so mixing two soluble solutions to form the insoluble precipitate directly is more practical.

True or False? The solid formed in a precipitation reaction is called the filtrate. (Extended Tier Only)

False. The insoluble solid formed is called the precipitate . The filtrate is the liquid that passes through the filter paper.

IGCSEScienceCambridge (CIE)Combined ScienceChemistryFlashcards7. Acids, Bases & SaltsPreparation of Salts

Preparation of Salts (Cambridge (CIE) IGCSE Combined Science: Chemistry): Flashcards

Exam code: 0653

1/17

0Still learning

Know0

FrontPreparing Soluble Salts
What is a salt?

Was this flashcard helpful?

Cards in this collection (17)

What is a salt?
A salt is a compound formed when the hydrogen atom(s) in an acid are replaced by a metal ion or ammonium ion. For example, replacing H in HCl with sodium gives sodium chloride (NaCl).
What two factors determine which method is used to prepare a soluble salt?
The method depends on the solubility of the salt and whether the base is soluble (an alkali) or insoluble. Soluble bases require titration; insoluble reactants use the excess solid method.
When preparing a soluble salt using excess insoluble base, the unreacted solid is removed by .......... and the salt is obtained by crystallisation.
When preparing a soluble salt using excess insoluble base, the unreacted solid is removed by filtration and the salt is obtained by crystallisation.
True or False?
Titration is used to prepare a soluble salt from a soluble alkali because excess alkali cannot be removed by filtration.
True.
Since alkalis are soluble, any excess would remain in the salt solution and could not be filtered off. Titration finds the exact volume of acid needed to neutralise the alkali, so no excess remains.
In a titration to prepare a pure soluble salt, why is the final titration repeated without indicator?
The indicator is omitted in the final titration so that it does not contaminate the pure salt solution. The volume of acid needed is already known from the first titration, so no indicator is required.
To prepare copper(II) sulfate, .......... acid is warmed and excess .......... is added until no more dissolves, then the mixture is filtered.
To prepare copper(II) sulfate, sulfuric acid is warmed and excess copper(II) oxide is added until no more dissolves, then the mixture is filtered.
How is the name of the salt produced in a reaction determined?
The first part of the salt name comes from the metal (or metal oxide/carbonate) and the second part comes from the acid. For example, hydrochloric acid always gives salts ending in chloride.
True or False?
When using excess metal to prepare a salt, the excess metal is removed by evaporation.
False.
Excess metal is a solid and is removed by filtration. Evaporation is used afterwards to concentrate the salt solution before crystallisation.
Describe how to check that a salt solution is saturated and ready to crystallise.
Dip a cold glass rod into the hot solution. If crystals form on the rod, the solution is saturated and ready to be left to crystallise.
What is a precipitation reaction? (Extended Tier Only)
A precipitation reaction is a reaction in which two soluble solutions are mixed and an insoluble solid (the precipitate) forms. It is used to prepare insoluble salts.
Why must both reactants be soluble when preparing an insoluble salt by precipitation? (Extended Tier Only)
Both reactants must be soluble so they can mix freely in solution, allowing the ions to collide and react. If either reactant were insoluble, the ions could not come into contact to form the precipitate.
To prepare an insoluble salt, two .......... solutions are mixed, and the precipitate is collected by .......... . (Extended Tier Only)
To prepare an insoluble salt, two soluble solutions are mixed, and the precipitate is collected by filtration.
True or False?
After filtering an insoluble salt, it should be washed with distilled water before drying. (Extended Tier Only)
True.
Washing with distilled water removes traces of the other soluble salts from the reaction. This ensures the final product is pure.
Write a word equation for the preparation of lead(II) sulfate by precipitation. (Extended Tier Only)
lead(II) nitrate + potassium sulfate → lead(II) sulfate + potassium nitrate
Lead(II) sulfate is the insoluble precipitate that forms when these two soluble solutions are mixed.
Steps for preparing an insoluble salt:
1. Mix two .......... aqueous solutions.
2. Filter to collect the precipitate.
3. Wash with .......... water.
4. Dry the solid. (Extended Tier Only)
Steps for preparing an insoluble salt:
1. Mix two soluble aqueous solutions.
2. Filter to collect the precipitate.
3. Wash with distilled water.
4. Dry the solid.
Why is the precipitation method used to prepare insoluble salts rather than the excess solid or titration method? (Extended Tier Only)
The excess solid and titration methods produce salts in solution, which can only be recovered if the salt is soluble. An insoluble salt would simply settle out as a solid, so mixing two soluble solutions to form the insoluble precipitate directly is more practical.
True or False?
The solid formed in a precipitation reaction is called the filtrate. (Extended Tier Only)
False.
The insoluble solid formed is called the precipitate. The filtrate is the liquid that passes through the filter paper.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:The Characteristic Properties of Acids & BasesNext:The Periodic Table & Trends