Preparation Of Salts

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Apuntes de la lección

Naming Salts

A salt is formed when the hydrogen atom in an acid is replaced by a metal or ammonium ion.
The name of a salt has two parts: first from the metal/metal oxide/carbonate, second from the acid.
Hydrochloric acid produces chlorides; sulfuric acid produces sulfates; nitric acid produces nitrates.
Example: sodium hydroxide + hydrochloric acid → sodium chloride.

Method A1: Excess Metal

Used for metals that react with dilute acids (e.g., Mg + H₂SO₄).
Add dilute acid to a beaker, then add metal in small pieces until no more reacts (metal in excess).
Filter to remove excess metal; heat the filtrate gently until concentrated.
Leave to crystallise, decant excess liquid, dry crystals with filter paper.
Example: Mg(s) + H₂SO₄(aq) → MgSO₄(aq) + H₂(g).

Preparing a soluble salt by the excess solid method

Method A2: Excess Insoluble Base

Used for insoluble bases such as metal oxides (e.g., CuO).
Warm dilute acid gently, add insoluble base slowly while stirring until no more reacts (base in excess).
Filter to remove excess base; heat filtrate until concentrated.
Crystallise, decant, and dry crystals.
Example: CuO(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l).

Preparing a soluble salt by the excess solid method

Method A3: Excess Insoluble Carbonate

Used for insoluble metal carbonates (e.g., CaCO₃).
Warm dilute acid, add carbonate slowly until no more reacts (carbonate in excess).
Filter, heat filtrate, crystallise, and dry.
Example: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l).

Preparing a soluble salt by the excess solid method

Method B: Titration (Soluble Alkali)

Used for soluble bases like NaOH.
Pipette alkali into conical flask, add indicator (e.g., phenolphthalein).
Add acid from burette until colour change (end point); record volume.
Repeat without indicator using same volume of acid.
Heat neutral solution to concentrate, crystallise, and dry.
Example: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l).

Preparing a soluble salt by titration

Preparing Insoluble Salts (Precipitation)

Extended tier only: use precipitation reaction between two soluble reactants.
Mix aqueous solutions of two soluble salts; insoluble salt forms as precipitate.
Filter to collect precipitate, wash with distilled water, dry in warm oven.
Example: Pb(NO₃)₂(aq) + K₂SO₄(aq) → PbSO₄(s) + 2KNO₃(aq).

Preparing an insoluble salt by precipitation

Hydrated & Anhydrous Salts

Hydrated salts contain water within their crystal structure (e.g., blue CuSO₄·5H₂O).
Anhydrous salts contain no water (e.g., white CuSO₄).
Heating hydrated copper(II) sulfate removes water, turning it white (dehydration).
Adding water to anhydrous copper(II) sulfate reverses the reaction, turning it blue.
Equation: hydrated CuSO₄ ⇌ anhydrous CuSO₄ + water.

Dehydration of hydrated copper(II) sulfate

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Preguntas de práctica

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1.Which method is used to prepare a soluble salt when the base is soluble (an alkali)?
Easy
- AExcess metal method
- BExcess insoluble base method
- CExcess insoluble carbonate method
- DTitration method
2.What is the name of the salt formed when zinc oxide reacts with sulfuric acid?
Easy
3.Complete the sentence about naming salts.
Easy
The name of a salt has two parts: the first part comes from the ____ or metal oxide or metal carbonate, and the second part comes from the ____.
4.A salt is a compound formed when the hydrogen atom in an acid is replaced by a metal or ammonium ion.
Easy
True or false?
5.In the preparation of magnesium sulfate crystals, if 0.24 g of magnesium reacts completely with excess sulfuric acid, calculate the maximum mass of magnesium sulfate (MgSO4) that can be obtained. (Ar: Mg=24, S=32, O=16)
Hard
- A2.2
- B1.2
- C3.2
- D0.2
6.Arrange the following steps in the correct order for preparing a soluble salt using the excess insoluble base method.
Medium
- Filter the mixture to remove excess base
- Heat the filtrate to concentrate the solution
- Add the insoluble base to warm dilute acid while stirring
- Leave the concentrated solution to crystallize
7.Match each acid to the salt it produces.
Easy
- Hydrochloric acid
- Sulfuric acid
- Nitric acid
- Sulfate
- Chloride
- Nitrate
8.Which of the following is the correct equation for the preparation of calcium chloride using excess calcium carbonate?
Medium
- ACaCO3 + 2HCl → CaCl2 + CO2 + H2O
- BCaCO3 + HCl → CaCl2 + CO2 + H2O
- CCaCO3 + 2HCl → CaCl2 + H2 + CO2
- DCaCO3 + HCl → CaCl2 + H2O + CO

Más preguntas

9.State one reason why an indicator is used in the titration method for preparing soluble salts.
Easy
10.When preparing an insoluble salt by precipitation, both reactants must be insoluble in water.
Medium
True or false?
11.Complete the sentence about hydrated and anhydrous salts.
Easy
Hydrated copper(II) sulfate is ____ in colour, while anhydrous copper(II) sulfate is ____.
12.Give the chemical equation for the dehydration of hydrated copper(II) sulfate. Use state symbols.
Medium
13.What is the name of the salt formed when calcium carbonate reacts with hydrochloric acid?
Easy
- Acalcium chloride
- Bcalcium sulfate
- Ccalcium nitrate
- Dcalcium carbonate
14.Which method should be used to prepare a soluble salt when the base is insoluble?
Easy
- Aexcess solid method
- Btitration method
- Cprecipitation method
- Ddistillation method
15.In the preparation of copper(II) sulfate crystals from copper(II) oxide and sulfuric acid, why is excess copper(II) oxide added?
Medium
- Ato ensure all the acid reacts
- Bto speed up the reaction
- Cto make the solution more concentrated
- Dto prevent the salt from decomposing
16.Anhydrous copper(II) sulfate is blue.
Easy
True or false?
17.Which of the following is a hydrated salt?
Easy
- ACuSO4·5H2O
- BNaCl
- CCaCO3
- DPbSO4
18.Which of the following are steps in the preparation of an insoluble salt by precipitation? (Select all that apply)
Medium
- AMix aqueous solutions of two soluble salts
- BTitrate acid with alkali using an indicator
- CFilter to remove the precipitate
- DWash the precipitate with distilled water
- EHeat the solution to crystallize
19.Arrange the following steps in the correct order for preparing a soluble salt by the excess solid method (using an insoluble base).
Medium
- Filter the mixture to remove excess solid.
- Add the insoluble base to warm dilute acid until no more reacts.
- Heat the filtrate gently to concentrate the solution.
- Leave the concentrated solution to crystallize.
20.Which method should be used to prepare a soluble salt when the base is soluble (an alkali)?
Easy
- AExcess metal method
- BExcess insoluble base method
- CTitration method
- DPrecipitation method
21.A student prepares a sample of zinc sulfate by reacting zinc oxide with dilute sulfuric acid. After filtering the excess zinc oxide, the student heats the filtrate until it is concentrated and then leaves it to crystallise. The crystals obtained are hydrated. What is the formula of the hydrated zinc sulfate?
Medium
- AZnSO₄
- BZnSO₄·H₂O
- CZnSO₄·7H₂O
- DZnSO₄·5H₂O
22.In an experiment to prepare a soluble salt by the excess solid method, a student adds excess copper(II) oxide to warm dilute sulfuric acid. After filtering, the filtrate is heated to concentrate the solution. The student then leaves the solution to crystallise. Which statement explains why the solution must be concentrated before crystallisation?
Medium
- ATo remove all water so that anhydrous crystals form
- BTo increase the concentration of copper(II) sulfate so that crystals form on cooling
- CTo decompose any excess copper(II) oxide
- DTo increase the rate of filtration
23.Which of the following are suitable methods for preparing a soluble salt? (Select all that apply)
Medium
- AReacting an acid with an excess of an insoluble metal oxide
- BReacting an acid with an excess of a metal carbonate
- CReacting an acid with an alkali using titration
- DReacting an acid with an excess of a soluble metal
- EReacting two soluble salts to form a precipitate
24.Match each acid to the type of salt it produces.
Easy
- Hydrochloric acid
- Sulfuric acid
- Nitric acid
- Chloride
- Sulfate
- Nitrate
25.Arrange the following steps in the correct order for preparing a soluble salt by the excess insoluble base method.
Medium
- Heat the filtrate to concentrate the solution
- Add the insoluble base to warm acid until no more reacts
- Filter the mixture to remove excess base
- Leave the concentrated solution to crystallise
26.A student prepares calcium chloride by reacting excess calcium carbonate with dilute hydrochloric acid. After filtering, the filtrate is heated to dryness. The residue is found to be calcium chloride but it is not pure. What is the most likely impurity?
Medium
- ACalcium carbonate
- BCalcium hydroxide
- CCalcium oxide
- DHydrochloric acid
27.In the preparation of copper(II) sulfate crystals from copper(II) oxide and sulfuric acid, after filtering the excess copper(II) oxide, the filtrate is heated gently until it is concentrated. How can you test that the solution is saturated?
Medium
- ADip a cold glass rod into the solution and see if crystals form on the end.
- BAdd more copper(II) oxide and see if it dissolves.
- CHeat the solution until it boils vigorously.
- DMeasure the pH of the solution with indicator paper.
28.When preparing an insoluble salt by precipitation, both reactants must be soluble in water.
Easy
True or false?
29.What is the first part of a salt's name derived from?
Easy
- AThe acid used
- BThe metal, metal oxide or metal carbonate used
- CThe colour of the salt
- DThe solubility of the salt
30.Anhydrous copper(II) sulfate is white. What colour is hydrated copper(II) sulfate?
Easy
- AWhite
- BBlue
- CGreen
- DColourless
31.In a titration to prepare a soluble salt, why is the titration repeated without indicator?
Medium
- ATo obtain a larger volume of salt solution
- BTo avoid contamination by the indicator
- CTo check the accuracy of the burette
- DTo speed up the reaction
32.Hydrated copper(II) sulfate is blue and anhydrous copper(II) sulfate is white.
Easy
True or false?
33.Arrange the following steps in the correct order for preparing a soluble salt by the titration method.
Medium
- Add indicator to alkali
- Titrate with acid until colour change
- Repeat without indicator
- Heat neutral solution to crystallise
34.In the preparation of an insoluble salt by precipitation, both reactants must be soluble in water.
Easy
True or false?
35.Arrange the following steps in the correct order for preparing an insoluble salt by precipitation.
Medium
- Mix solutions of two soluble salts
- Filter to collect precipitate
- Wash precipitate with distilled water
- Dry the precipitate
36.Which of the following statements about preparing copper(II) sulfate crystals from copper(II) oxide and sulfuric acid are correct? (Select all that apply)
Medium
- AExcess copper(II) oxide is added to ensure all acid reacts
- BThe mixture is filtered to remove excess copper(II) oxide
- CThe filtrate is heated to dryness to obtain crystals
- DThe crystals are dried using filter paper
37.A student prepares a sample of zinc sulfate by reacting zinc oxide with dilute sulfuric acid. After filtering the excess zinc oxide, the student heats the filtrate until it becomes concentrated. Which statement about this process is correct?
Medium
- AThe reaction produces hydrogen gas.
- BExcess zinc oxide is added to ensure all acid is used up.
- CThe filtrate is heated to dryness to obtain crystals directly.
- DZinc oxide is soluble in water.
38.Which statement about the preparation of an insoluble salt by precipitation is correct?
Medium
- ABoth reactants must be insoluble in water.
- BThe precipitate is obtained by evaporating the mixture.
- CThe precipitate is washed with distilled water to remove impurities.
- DThe reaction is an example of neutralisation.
39.A student uses a titration to prepare sodium chloride from sodium hydroxide and hydrochloric acid. 25.0 cm³ of 0.50 mol/dm³ sodium hydroxide requires 25.0 cm³ of 0.50 mol/dm³ hydrochloric acid for neutralisation. What is the concentration of the sodium chloride solution formed, assuming the total volume is 50.0 cm³?
Hard
- A0.25 mol/dm³
- B0.50 mol/dm³
- C1.00 mol/dm³
- D0.125 mol/dm³
40.In the preparation of copper(II) sulfate crystals from copper(II) oxide and dilute sulfuric acid, why is excess copper(II) oxide added?
Easy
- ATo ensure all the acid reacts
- BTo speed up the reaction
- CTo make the solution more concentrated
- DTo prevent the formation of copper(II) sulfate
41.Which of the following is the correct name for the salt formed when zinc oxide reacts with nitric acid?
Easy
- AZinc nitrate
- BZinc nitride
- CZinc nitrite
- DZinc nitrogenate
42.Which of the following methods can be used to prepare a soluble salt? (Select all that apply)
Medium
- AAdding excess metal to dilute acid
- BMixing two soluble salt solutions that form a precipitate
- CAdding excess insoluble base to warm dilute acid
- DTitrating an alkali with an acid using an indicator
- EHeating a hydrated salt to drive off water
43.Match each acid to the name of the salt it produces.
Easy
- Hydrochloric acid
- Sulfuric acid
- Nitric acid
- Chloride
- Sulfate
- Nitrate
44.What is the name of the salt formed when zinc oxide reacts with nitric acid?
Easy
- AZinc nitrate
- BZinc nitrite
- CZinc nitride
- DZinc chloride
45.What is the colour of anhydrous copper(II) sulfate?
Easy
- ABlue
- BWhite
- CGreen
- DBlack
46.Calculate the maximum mass of magnesium sulfate (MgSO4) that can be obtained from 0.24 g of magnesium (Mg). [Ar: Mg = 24, S = 32, O = 16]
Hard
47.Calculate the mass of anhydrous copper(II) sulfate (CuSO₄) that can be obtained by heating 25.0 g of hydrated copper(II) sulfate (CuSO₄·5H₂O). [Ar: H=1, O=16, S=32, Cu=63.5]
Hard
48.Complete the sentence.
Easy
When preparing a soluble salt using the titration method, an ____ is added to the alkali to determine when the acid and alkali have exactly reacted.
49.Why is it necessary to repeat the titration without indicator when preparing a soluble salt by titration?
Medium
50.In a titration to prepare sodium chloride, 25.0 cm³ of 0.50 mol/dm³ sodium hydroxide requires 25.0 cm³ of 0.50 mol/dm³ hydrochloric acid for neutralisation. Calculate the mass of sodium chloride produced. [Ar: Na=23, Cl=35.5]
Medium
51.Describe how you would prepare a pure, dry sample of lead(II) sulfate from lead(II) nitrate and potassium sulfate.
Medium
52.Explain why excess copper(II) oxide is added to sulfuric acid when preparing copper(II) sulfate crystals.
Medium
53.Explain how you would prepare a pure, dry sample of lead(II) sulfate from lead(II) nitrate and potassium sulfate.
Medium
54.Calculate the maximum mass of magnesium sulfate (MgSO4) that can be obtained from 0.24 g of magnesium (Mg). [Ar: Mg = 24, S = 32, O = 16]
Medium
- A2.2 g
- B0.2 g
- C3.2 g
- D1.2 g
55.Calculate the mass of anhydrous copper(II) sulfate (CuSO₄) that can be obtained by heating 25.0 g of hydrated copper(II) sulfate (CuSO₄·5H₂O). [Ar: H=1, O=16, S=32, Cu=63.5]
Medium
- A16 g
- B18 g
- C15 g
- D17 g
56.In a titration to prepare sodium chloride, 25.0 cm³ of 0.50 mol/dm³ sodium hydroxide requires 25.0 cm³ of 0.50 mol/dm³ hydrochloric acid for neutralisation. Calculate the mass of sodium chloride produced. [Ar: Na=23, Cl=35.5]
Medium
- A2.731 g
- B-0.269 g
- C0.731 g
- D1.731 g

Tarjetas

What is a salt?

A salt is a compound formed when the hydrogen atom in an acid is replaced by a metal or ammonium ion.

How is a salt named?

The first part comes from the metal, metal oxide, or metal carbonate used; the second part comes from the acid.

What are the two main methods for preparing soluble salts?

Method A: using excess solid reactant (metal, insoluble base, or insoluble carbonate). Method B: using an alkali by titration.

When is Method A (excess solid) used for preparing a soluble salt?

Method A is used when the reactant is a solid in excess; unreacted solid is removed by filtration, then the salt is crystallised.

Describe the steps for preparing a soluble salt using excess metal (Method A1).

Add dilute acid to a beaker, add metal in small pieces while stirring until no more reacts, filter to remove excess metal, heat filtrate to concentrate, leave to crystallise, decant excess liquid, dry crystals with filter paper.

Give an example reaction for preparing a soluble salt using excess metal.

Magnesium + sulfuric acid → magnesium sulfate + hydrogen: Mg(s) + H₂SO₄(aq) → MgSO₄(aq) + H₂(g).

Describe the steps for preparing a soluble salt using excess insoluble base (Method A2).

Warm dilute acid gently, add insoluble base slowly while stirring until no more reacts, filter to remove excess base, heat filtrate to concentrate, leave to crystallise, decant excess liquid, dry crystals with filter paper.

Give an example reaction for preparing a soluble salt using excess insoluble base.

Copper(II) oxide + sulfuric acid → copper(II) sulfate + water: CuO(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l).

Describe the steps for preparing a soluble salt using excess insoluble carbonate (Method A3).

Warm dilute acid gently, add insoluble carbonate slowly while stirring until no more reacts, filter to remove excess carbonate, heat filtrate to concentrate, leave to crystallise, decant excess liquid, dry crystals with filter paper.

Give an example reaction for preparing a soluble salt using excess insoluble carbonate.

Calcium carbonate + hydrochloric acid → calcium chloride + carbon dioxide + water: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l).

When is Method B (titration) used for preparing a soluble salt?

Method B is used when the base is soluble (alkali), e.g., sodium hydroxide.

Describe the steps for preparing a soluble salt by titration (Method B).

Place alkali in conical flask with indicator, fill burette with acid, add acid slowly until indicator changes colour, repeat without indicator using same volume, heat neutral solution to concentrate, leave to crystallise, decant excess liquid, dry crystals.

Give an example reaction for preparing a soluble salt by titration.

Sodium hydroxide + hydrochloric acid → sodium chloride + water: NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l).

How do you check if a solution is saturated during crystallisation?

Dip a cold glass rod into the solution; if crystals form on the end, the solution is saturated.

How are insoluble salts prepared?

Insoluble salts are prepared by precipitation: mix aqueous solutions of two soluble salts, filter to obtain the precipitate, wash with distilled water, and dry.

What conditions are needed for preparing an insoluble salt by precipitation?

The solid salt (precipitate) must be insoluble in water, and the reactants must be soluble.

Give an example of preparing an insoluble salt by precipitation.

Lead(II) nitrate + potassium sulfate → lead(II) sulfate + potassium nitrate: Pb(NO₃)₂(aq) + K₂SO₄(aq) → PbSO₄(s) + 2KNO₃(aq).

What is a hydrated salt?

A hydrated salt is a salt that contains water within its crystal structure.

What is an anhydrous salt?

An anhydrous salt is a salt that contains no water in its structure.

Describe the colour change when hydrated copper(II) sulfate is heated.

Hydrated copper(II) sulfate is blue; upon heating it loses water and becomes white anhydrous copper(II) sulfate.

How can anhydrous copper(II) sulfate be converted back to hydrated copper(II) sulfate?

By adding water to anhydrous copper(II) sulfate, it rehydrates and turns blue again.

Write the reversible equation for the hydration/dehydration of copper(II) sulfate.

Hydrated copper(II) sulfate ⇌ anhydrous copper(II) sulfate + water.

What is the purpose of filtering in Method A?

To remove the excess solid reactant (metal, base, or carbonate) that did not react.

Why is the solution heated gently during crystallisation?

To concentrate the solution by evaporating some water, so that crystals form upon cooling.

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