Preparation Of Salts

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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.
Example: Replacing H in HCl with K gives KCl (potassium chloride).
The name of a salt has two parts: first part from the metal/metal oxide/carbonate, second part from the acid.
Hydrochloric acid produces chlorides; sulfuric acid produces sulfates; nitric acid produces nitrates.

Solubility Rules

All sodium, potassium, and ammonium salts are soluble.
All nitrates are soluble.
Most chlorides are soluble except silver chloride and lead(II) chloride.
Most sulfates are soluble except barium sulfate, calcium sulfate, and lead(II) sulfate.
Most carbonates are insoluble except those of sodium, potassium, and ammonium.
Most hydroxides are insoluble except those of sodium, potassium, and ammonium (calcium hydroxide is sparingly soluble).

Solubility of common salts

Preparing Soluble Salts – Method A (Excess Solid)

Use excess solid reactant (metal, insoluble base, or insoluble carbonate) with dilute acid.
Add solid until no more reacts, indicating excess.
Filter to remove unreacted solid; the filtrate is the salt solution.
Evaporate the filtrate gently until saturated (test with cold glass rod – crystals form).
Crystallise by leaving in a warm place, then decant excess liquid and dry crystals with filter paper.
Example (metal): Mg + H₂SO₄ → MgSO₄ + H₂.
Example (insoluble base): CuO + H₂SO₄ → CuSO₄ + H₂O.
Example (insoluble carbonate): CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O.

Preparing a soluble salt by the excess solid method

Preparing Soluble Salts – Method B (Titration)

Use titration when the base is soluble (alkali).
Pipette a known volume of alkali into a conical flask, add a few drops of indicator (e.g., phenolphthalein).
Fill a burette with acid, add slowly while swirling until the indicator changes colour (end point).
Repeat without indicator using the same volumes to obtain a neutral solution.
Evaporate, crystallise, decant, and dry the crystals as in Method A.
Example: NaOH + HCl → NaCl + H₂O.

Preparing a soluble salt by titration

Preparing Insoluble Salts (Extended Tier)

Insoluble salts are prepared by precipitation.
Mix aqueous solutions of two soluble salts that react to form the insoluble salt (precipitate).
Filter to collect the precipitate.
Wash the precipitate with distilled water to remove soluble impurities.
Dry the solid (e.g., in a 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 of crystallisation within their structure (e.g., CuSO₄·5H₂O, blue).
Anhydrous salts contain no water (e.g., CuSO₄, white).
Heating a hydrated salt drives off water of crystallisation, forming the anhydrous salt.
Adding water to an anhydrous salt rehydrates it (reversible reaction).
Water of crystallisation is shown in the formula with a dot: e.g., CoCl₂·6H₂O.

Dehydration of hydrated copper(II) sulfate

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Übungsfragen

Gratis-Vorschau — 8 von 45 Fragen. Registriere dich, um alle zu sehen.

1.When solid sodium chloride is mixed with water, sodium chloride solution forms. What name is given to the process of mixing a solid with water to form a solution?
Easy
- ACrystallising
- BDiluting
- CDissolving
- DMelting
2.Which salt is insoluble in water?
Easy
- ASodium chloride
- BPotassium nitrate
- CSilver chloride
- DAmmonium sulfate
3.A student reacts excess iron powder with sulfuric acid to prepare iron(II) sulfate. How would the student know when all the sulfuric acid has reacted?
Medium
- ANo more gas is produced and the mixture becomes neutral
- BThe solution turns blue
- CThe iron powder dissolves completely
- DA precipitate forms
4.Lead(II) sulfate is prepared by mixing aqueous lead(II) nitrate and aqueous potassium sulfate. What is the state symbol for lead(II) sulfate in the equation?
Easy
- A(aq)
- B(s)
- C(l)
- D(g)
5.What is the name of the salt formed when magnesium oxide reacts with sulfuric acid?
Easy
- AMagnesium sulfate
- BMagnesium sulfide
- CMagnesium sulfite
- DMagnesium oxide
6.In the preparation of a soluble salt using an excess solid method, what is the purpose of adding the solid in excess?
Medium
- ATo increase the rate of reaction
- BTo ensure all the acid reacts
- CTo produce more salt crystals
- DTo make the solution saturated
7.Which method should be used to prepare a soluble salt from a soluble base (alkali) and an acid?
Medium
- AExcess metal method
- BExcess insoluble base method
- CTitration method
- DPrecipitation method
8.Hydrated copper(II) sulfate is blue. When heated, it turns white. What is the white substance?
Easy
- AAnhydrous copper(II) sulfate
- BHydrated copper(II) sulfate
- CCopper(II) oxide
- DCopper metal

Mehr Fragen

9.Which of the following is an insoluble salt?
Easy
- ASodium carbonate
- BPotassium chloride
- CBarium sulfate
- DAmmonium nitrate
10.In the preparation of copper(II) sulfate crystals, copper(II) oxide is added to warm dilute sulfuric acid. After filtering, the filtrate is heated until concentrated. How can you test if the solution is saturated?
Medium
- ADip a cold glass rod into the solution and see if crystals form
- BMeasure the pH of the solution
- CAdd more copper(II) oxide and see if it dissolves
- DWeigh the solution
11.Which of the following is the correct method to obtain pure dry lead(II) sulfate from a mixture of lead(II) sulfate and water?
Medium
- AEvaporate the water to dryness
- BFilter, wash the residue with distilled water, and dry
- CDecant the liquid and heat the residue
- DCrystallise by cooling
12.What is the formula of hydrated copper(II) sulfate?
Easy
- ACuSO4
- BCuSO4·5H2O
- CCuSO4·H2O
- DCuSO4·10H2O
13.A student prepares magnesium sulfate crystals by reacting excess magnesium oxide with warm dilute sulfuric acid. After filtering, the filtrate is heated until a drop placed on a cold glass rod forms crystals. The solution is then left to crystallise. Which step is used to check that the solution is saturated?
Medium
- AHeating the solution until it boils
- BDipping a cold glass rod into the solution and looking for crystals
- CAdding a few drops of indicator
- DMeasuring the pH of the solution
14.A student prepares lead(II) sulfate by mixing aqueous lead(II) nitrate and aqueous potassium sulfate. The precipitate is filtered, washed with distilled water, and dried. Why is the precipitate washed with distilled water?
Medium
- ATo remove any soluble impurities such as potassium nitrate
- BTo dissolve the lead(II) sulfate
- CTo prevent the lead(II) sulfate from decomposing
- DTo increase the yield of lead(II) sulfate
15.A student uses titration to prepare sodium chloride crystals from sodium hydroxide and hydrochloric acid. Which piece of apparatus is used to measure the volume of acid added during the titration?
Easy
- APipette
- BBurette
- CMeasuring cylinder
- DConical flask
16.Hydrated copper(II) sulfate is heated until it turns white. The white solid is then left exposed to air and slowly turns blue again. Which statement explains this observation?
Medium
- AThe white solid absorbs water from the air to reform hydrated copper(II) sulfate
- BThe white solid reacts with oxygen in the air to form hydrated copper(II) sulfate
- CThe white solid decomposes to copper oxide and then rehydrates
- DThe white solid is anhydrous and remains white indefinitely
17.What is the name of the salt formed when zinc oxide reacts with sulfuric acid?
Easy
- AZinc sulfate
- BZinc sulfide
- CZinc sulfite
- DZinc oxide sulfate
18.Which method should be used to prepare a pure sample of calcium chloride from calcium carbonate and dilute hydrochloric acid?
Medium
- ATitration using an indicator
- BAdding excess calcium carbonate to the acid, filtering, then crystallising
- CMixing aqueous solutions of two soluble salts and filtering
- DHeating the mixture to dryness
19.A student prepares a sample of potassium nitrate by neutralising nitric acid with potassium hydroxide solution. The pH is measured after each addition of KOH. The results show a sharp pH change from 2.7 to 11.0 between 24.5 cm³ and 25.5 cm³ of KOH added. What is the approximate volume of KOH needed to neutralise the acid?
Hard
- A24.5 cm³
- B25.0 cm³
- C25.5 cm³
- D30.0 cm³
20.In the preparation of copper(II) sulfate crystals, copper(II) oxide is added to warm dilute sulfuric acid until no more dissolves. After filtering, the filtrate is heated gently to concentrate it. Why must the solution not be heated to dryness?
Medium
- AThe salt would decompose
- BThe salt would become anhydrous and lose water of crystallisation
- CThe salt would react with the air
- DThe salt would not crystallise properly
21.A student prepares magnesium sulfate crystals by reacting excess magnesium with dilute sulfuric acid. After the reaction stops, the mixture is filtered. The filtrate is then heated until a small sample forms crystals on a cold glass rod. What is the purpose of this test?
Medium
- ATo check that all the acid has reacted
- BTo check that the solution is saturated
- CTo check that the magnesium is in excess
- DTo check that the crystals are dry
22.Which of the following is a hydrated salt?
Easy
- ACuSO₄
- BCuSO₄·5H₂O
- CNaCl
- DKNO₃
23.A student prepares lead(II) sulfate by mixing aqueous lead(II) nitrate and aqueous potassium sulfate. The mixture is filtered, and the residue is washed with distilled water and dried. What is the purpose of filtration?
Medium
- ATo separate the soluble lead(II) sulfate from the solution
- BTo separate the insoluble lead(II) sulfate from the solution
- CTo remove the potassium nitrate from the mixture
- DTo collect the potassium sulfate
24.A student prepares a solution of magnesium sulfate by reacting excess magnesium oxide with warm dilute sulfuric acid. After filtering, the filtrate is heated until it is concentrated. How can the student check that the solution is saturated?
Medium
- ADip a cold glass rod into the solution and see if crystals form on the end.
- BMeasure the temperature of the solution.
- CAdd a small amount of water and see if it dissolves.
- DTest the pH of the solution.
25.Which salt can be prepared by mixing two aqueous solutions and collecting the precipitate?
Medium
- ALead(II) sulfate
- BSodium chloride
- CPotassium nitrate
- DCopper(II) sulfate
26.A student adds excess zinc oxide to warm dilute nitric acid until no more reacts. After filtering, what is the name of the salt in the filtrate?
Medium
- AZinc nitrate
- BZinc nitrite
- CZinc nitride
- DZinc oxide
27.A student uses titration to prepare sodium chloride crystals from sodium hydroxide solution and hydrochloric acid. Which indicator is used to determine the end point?
Medium
- APhenolphthalein
- BMethyl orange
- CUniversal indicator
- DLitmus
28.A student wants to prepare pure dry crystals of hydrated copper(II) sulfate from copper(II) oxide and dilute sulfuric acid. Which method should be used?
Medium
- AAdd excess copper(II) oxide to warm acid, filter, then crystallise the filtrate.
- BAdd excess acid to copper(II) oxide, then evaporate to dryness.
- CMix copper(II) oxide and acid, then filter and wash the residue.
- DTitrate the acid with copper(II) oxide using an indicator.
29.Hydrated copper(II) sulfate is blue. When heated, it turns white. Which statement explains this change?
Medium
- AWater of crystallisation is lost, forming anhydrous copper(II) sulfate.
- BThe copper(II) ions are reduced to copper(I).
- CSulfur dioxide gas is released.
- DThe sulfate ions decompose to sulfur and oxygen.
30.In the preparation of copper(II) sulfate crystals, copper(II) oxide is added to warm dilute sulfuric acid until no more dissolves. After filtering, the filtrate is heated until concentrated and then left to cool. Why is the acid warmed before adding the oxide?
Easy
- Ato increase the rate of reaction
- Bto make the acid more concentrated
- Cto prevent the formation of hydrogen gas
- Dto ensure the oxide dissolves
31.A student plans to prepare pure dry crystals of hydrated magnesium sulfate, MgSO4·7H2O, from a solution of magnesium sulfate. Which sequence of steps is correct?
Medium
- Aheat to evaporate water until crystals form, then dry with filter paper
- Bheat to dryness, then add water
- Cfilter, then heat to evaporate all water
- Dleave to crystallise, then heat to remove water of crystallisation
32.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?
33.Which acid is used to prepare a salt ending in 'sulfate'?
Easy
- AHydrochloric acid
- BNitric acid
- CSulfuric acid
- DPhosphoric acid
34.Which of the following methods are used to prepare soluble salts? (Select all that apply.)
Medium
- AExcess solid reactant
- BPrecipitation
- CTitration with an alkali
- DFiltration only
35.All nitrates are soluble in water.
Easy
True or false?
36.What is the colour of hydrated copper(II) sulfate?
Easy
- AWhite
- BBlue
- CGreen
- DColourless
37.All sodium, potassium, and ammonium salts are soluble in water.
Easy
True or false?
38.Which method is used to prepare an insoluble salt?
Easy
- AExcess solid method
- BTitration
- CPrecipitation
- DCrystallisation
39.Silver chloride is soluble in water.
Easy
True or false?
40.Match each salt preparation method to the correct description.
Medium
- Excess metal method
- Excess insoluble base method
- Titration method
- Precipitation method
- Used for soluble bases like NaOH
- Produces an insoluble salt
- Used for metals that react with dilute acids
- Used for insoluble bases like metal oxides
41.Arrange the following steps in the correct order for preparing copper(II) sulfate crystals using the excess insoluble base method.
Medium
- Filter the mixture to remove excess copper(II) oxide
- Add copper(II) oxide to warm dilute sulfuric acid until no more reacts
- Heat the filtrate gently until concentrated
- Leave the concentrated solution to crystallize
- Dry the crystals with filter paper
42.Complete the sentence.
Easy
The name of a salt has two parts: the first part comes from the ____ , and the second part comes from the ____.
43.Complete the sentence about hydrated and anhydrous salts.
Easy
Hydrated copper(II) sulfate is ____. When heated, it turns ____ because water of crystallisation is removed.
44.A student prepares hydrated magnesium sulfate (MgSO₄·7H₂O) by crystallisation. If the student starts with 0.50 mol of magnesium sulfate, calculate the mass of hydrated crystals obtained. (Relative formula mass: MgSO₄·7H₂O = 246 g/mol)
Medium
45.A student prepares hydrated magnesium sulfate (MgSO₄·7H₂O) by crystallisation. If the student starts with 0.50 mol of magnesium sulfate, calculate the mass of hydrated crystals obtained. (Relative formula mass: MgSO₄·7H₂O = 246 g/mol)
Medium
- A111 g
- B147 g
- C135 g
- D123 g

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