Acids Bases and Salts Exe-3(B) Concise Class-10 ICSE Chemistry Selina Solutions Chapter-3. We Provide Step by Step Answer of Exe-3(B) Questions of Exercise-3 for ICSE Class-10. The given Solutions is according to the Latest editions. Visit official Website CISCE for detail information about ICSE Board Class-10.

Acids Bases and Salts Exe-3(B) Concise Class-10 ICSE Chemistry Selina Solutions Chapter-3

Board	ICSE
Book / Publication	Concise / Selina
Subject	Chemistry
Class	10th
Writer	Dr SP Singh
Chapter-3	Acids Bases and Salts
Topics	Exe-3(B)
Edition	2025-2026

Exe-3(B) Questions on Acids Bases and Salts

Page-56

Que-1: Define the following and give two examples in each case:

(a) a normal salt, (b) an acid salt, (c) a mixed salt.

Ans: (a) A normal salt:
Normal salts are the salts formed by the complete replacement of the ionizable hydrogen atoms of an acid by a metallic or an ammonium ion.
(b) An acidic salt:
Acid salts are formed by the partial replacement of the ionizable hydrogen atoms of a polybasic acid by a metal or an ammonium ion.
(c) A mixed salt:
Mixed salts are those salts that contain more than one basic or acid radical.
Examples:
(a) A Normal salt: Na₂SO₄ , NaCl
(b) An acid salt: NaHSO₄ , Na₂HPO₄
(c) A mixed salt: NaKCO₃ , CaOCl₂

Que-2: Answer the following questions related to salts and their preparations:

(a) What is a salt?
(b) What kind of salt is prepared by precipitation?
(c) Name a salt prepared by the direct combination. Write an equation for the reaction that takes place in preparing the salt you have named.
(d) Name the procedure used to prepare a sodium salt such as sodium sulphate.

Ans: 
(a) Salt is a compound formed by the partial or total replacement of the ionizable hydrogen atoms of an acid by a metallic ion or an ammonium ion.
(b) An insoluble salt can be prepared by precipitation.
(c) A salt prepared by direct combination is Iron(III) chloride.
Reaction:
2Fe +3Cl₂ 2FeCl₃
(d) By neutralizing sodium carbonate or sodium hydroxide with dilute sulphuric acid:
Na₂CO₃ + H₂SO₄ → Na₂SO₄ + H₂O + CO₂
2 NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

Que-3: Explain the following method with example

(a) Direct combination
(b) Displacement method
(c) Double Decomposition (precipitation)
(d) neutralisation of insoluble salt
(e) Neutralisation of alkali (titration)

Ans: 
(a) Direct combination
A reaction in which two or more substances combine. together to form a single substance is called a combination reaction
Fe + S —–FeS
(b) Displacement method
Reactions in which the more reactive element displaces the less reactive element from its compound are called displacement reactions.
For example:
Zinc displaces copper in copper sulphate to form zinc sulphate.
Zn_(s)   +     CuSO_{4 (aq)}           →               ZnSO_{4 (aq)}   +       Cu_(s)
Zinc      Copper sulphate                      Zinc sulphate        Copper
(c) Double Decomposition (precipitation)
Reactions in which ions of the reactants exchange places to form two new compounds, are called double displacement reactions.
For example:
Sodium hydroxide reacts with hydrochloric acid to form sodium chloride and water.
NaOH_(aq)      +         HCl_(aq)        →     NaCl_(aq)         +        H₂O_(l)
(d) neutralisation of insoluble salt

1. An insoluble salt can be prepared by a precipitation method through a double decomposition reaction.
2. In this method two aqueous solutions of two different soluble salts are mixed together to form the insoluble salt. The insoluble salt is formed as a precipitate and can be obtained by filtration.
3. (a) The first solution must have a soluble salt which contains the cation of the insoluble salt.
   (b) The second solution must have a soluble salt which contains the anion of the insoluble salt.

(e) Neutralisation of alkali (titration)
The concentration of an acid or alkali can be calculated by carrying out an experiment called a titration.
Materials: The apparatus needed includes:

• a pipette to accurately measure a certain volume of acid or alkali
• a pipette filler to use the pipette safely
• a conical flask to contain the liquid from the pipette
• a burette to add small, measured volumes of one reactant to the other reactant in the conical flask

Apparatus needed to carry out a titration

Method:

This is an outline method for carrying out a titration in which an acid is added to alkali.

1. Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask.
2. Add a few drops of indicator and put the conical flask on a white tile.
3. Fill the burette with acid and note the starting volume.
4. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
5. Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading.
6. Repeat steps 1 to 5 until you get concordant readings (see explanation below).

The same method works for adding an alkali to an acid – just swap around the liquids that go into the conical flask and burette.

Que-4: How would you prepare :

(a) Copper sulphate crystals from mixture of charcoal and black copper oxide,
(b) Zinc sulphate crystals from Zinc dust (powered Zinc and Zinc oxide)
(c) sodium hydrogen carbonate crystals
(d) Calcium sulphate from calcium carbonate

Ans: 
(a) Copper sulphate crystals from a mixture of charcoal and black copper oxide:
The carbon in the charcoal reduces the black copper oxide to reddish-brown copper. The lid must not be removed until the crucible is cool or the hot copper will be re-oxidized by air.
Take dilute sulphuric acid in a beaker and heat it on wire gauze. Add cupric oxide in small quantities at a time, with stirring till no more of it dissolves and the excess compound settles to the bottom.
Filter it hot and collect the filtrate in a china dish. Evaporate the filtrate by heating to the point of crystallization and then allow it to cool and collect the crystals of copper sulphate pentahydrate.
Reaction: CuO + H₂SO₄ CuSO₄ + H₂O
CuSO₄ + 5H₂O CuSO_4. 5H₂O
(b) Zinc sulphate crystals from Zinc dust:
Take dilute sulphuric acid in a beaker and heat it on wire gauze. Add some granulated zinc pieces with constant stirring. Add till the Zinc settles at the base of the beaker. Effervescences take place because of the liberation of hydrogen gas. When effervescence stops, it indicates that all the acid has been used up. The excess of zinc is filtered off. Collect the solution in a china dish and evaporate the solution to get crystals. Filter, wash them with water and dry them between the folds of paper. The white needle crystals are of hydrated Zinc sulphate.
Reaction: Zn + H₂SO₄ ZnSO₄ + H₂
ZnSO₄ +7 H₂O ZnSO_4. 7 H₂O
(c) Lead sulphate from metallic lead:
Metallic lead is converted to lead oxide by oxidation. Then lead sulphate is prepared from insoluble lead oxide, by first converting it into soluble lead nitrate. Then the lead nitrate solution is treated with sulphuric acid to obtain white ppt. of Lead sulphate.
Reaction:
PbO +2HNO₃ Pb(NO₃)₂ + H₂O
Pb(NO₃)₂ + H₂SO₄ PbSO₄ + 2HNO₃
(d)Sodium hydrogen carbonate crystals:
Dissolve 5 grams of anhydrous sodium carbonate in about 25 ml of distilled water in a flask. Cool the solution by keeping the flask in a freezing mixture. Pass carbon dioxide gas in the solution. Crystals of sodium bicarbonate will precipitate out after some time. Filter the crystals and dry it in folds of filter paper.
Reaction: Na₂CO₃ + CO₂ + H₂O 2NaHCO₃

Que-5: The following is the list of methods for the preparation of salts.

A-Direct combination of two elements.
B-reaction of dilute acid with a metal.
C-reaction of dilute acid with an insoluble base.
D-Titration of dilute acid with a solution of soluble base.
E- reaction of two solutions of salts to form a precipitate.
Choose from the above list A to E , the best method of preparing the following salts by giving a suitable equation in each case:

1. Anhydrous ferric chloride,
2. Lead chloride,
3. Sodium sulphate,
4. Copper sulphate.

Ans: 
1. Anhydrous ferric chloride — A. (Direct combination of two elements)
2Fe + 3Cl₂ ⟶ 2FeCl₃
2. Lead chloride — E. (Reaction of two solutions of salts to form a precipitate)
Pb(NO₃)₂ + 2NaCl ⟶ PbCl₂ + 2NaNO₃
3. Sodium sulphate — D. (Titration of dilute acid with a solution of soluble base)
2NaOH + H₂SO₄ ⟶ Na₂SO₄ + 2H₂O
4. Copper sulphate — C. (reaction of a dilute acid with an insoluble base)
Cu(OH)₂ + H₂SO₄ ⟶ CuSO₄ + 2H₂O

Que-6: Name:

(a) A chloride which is insoluble in cold water but dissolves in hot water,
(b) A chloride which is insoluble,
(c) Two sulphates which are insoluble,
(d) A basic salt,
(e) An acidic salt,
(f) A mixed salt,
(g) A complex salt,
(h) A double salt,
(i) a salts whose solubility increases with temperature,
(j) A salt whose solubility decreases with temperature.

Ans: 
(a) Lead chloride
(b) Silver chloride
(c) Barium sulphate and lead sulphate
(d) Basic lead chloride
(e) Sodium hydrogen sulphate
(f) Sodium potassium carbonate
(g) Sodium argentocyanide
(h) Potash alum
(i) Potassium bromide and potassium chloride
(j) Calcium sulphate

Que-7: Fill in the blanks with suitable words:

An acid is a compound which when dissolved in water forms hydronium ions as the only …………… ions. A base is a compound which is soluble in water and contains …………….. ions. A base reacts with an acid to form a …………….. and water only. This type of reaction is known as …………….

Ans: An acid is a compound which when dissolved in water forms hydronium ions as the only positively charged ions. A base is a compound which is soluble in water and contains hydroxide ions. A base reacts with an acid to form a salt and water only. This type of reaction is known as neutralisation.

Que-8: What would you observe when:

(a) Blue litmus is introduced into a solution of hydrogen chloride gas.
(b) Red litmus paper is introduced into a solution of ammonia in water
(c) Red litmus paper is introduced in Caustic soda solution?

Ans: 
(a) Blue litmus will turn into red which will indicate the solution to be acidic.
(b) No change will be observed.
(c) Red litmus will turn into blue will indicate the solution to be basic.

Que-9: Explain why:

(a) It is necessary to find out the ratio of reactants required in the preparation of sodium sulphate.
(b) Fused calcium chloride is used in the preparation of FeCl₃.
(c) Anhydrous FeCl₃ cannot be prepared by heating hydrated iron (III) chloride.

Ans: 
(a) Since sodium hydroxide and sulphuric acid are both soluble, an excess of either of them cannot be removed by filtration. Therefore it is necessary to find out on small scale, the ratio of solutions of the two reactants.
(b) As iron chloride is highly deliquescent, so it is kept dry with the help of fused calcium chloride.
(c) On heating the hydrate, HCl acid is released and basic salt (FeOCl) or ferric oxide remains. Hence, anhydrous ferric chloride cannot be prepared by heating the hydrate.

Column A	Column B
Zinc sulphate	Precipitation
Ferrous sulphide	Oxidation
Barium sulphate	Displacement
Ferric sulphate	Neutralisation
Sodium sulphate	Synthesis.

Ans:
Zinc Sulphate — Displacement
Zn + H₂SO₄ ⟶ ZnSO₄ + H₂
Ferrous sulphide — Synthesis
Fe + S ⟶ FeS
Barium sulphate — Precipitation
Na₂SO₄ + BaCl₂ ⟶ BaSO₄ ↓ + 2NaCl
Ferric Sulphate — Displacement
Fe + H₂SO₄ ⟶ FeSO₄ + H₂
Sodium sulphate — Neutralisation
2NaOH + H₂SO₄ ⟶ Na₂SO₄ + 2H₂O

Que-11:

(a) Give the pH value of pure water. Does it change if common salt is added to it?
(b) Classify the following solutions as acids, bases or salts. Ammonium hydroxide, barium chloride, sodium chloride, sodium hydroxide, H₂SO₄ and HNO₃

Ans:
(a) pH of pure water is 7 at 25^oC. No, the pH does not change when common salt is added.
(b) Acids: H₂SO₄ and HNO₃
Bases: Ammonium hydroxide and sodium hydroxide.
Salts: Barium chloride and sodium chloride.

Que-12: Complete the following table and write one equation for each to justify the statement:

Reactants	Products	Method
Soluble base + Acid (dil)	Salt + water	Neutralisation Titration
Metal + Non-metal	Salt (soluble/insoluble)	……………
Insoluble base +	Salt (soluble) + water	…………….
Active metal + Acid (dil)	………… + …………	…………….
Soluble salt solution (A) +	Precipitated salt +	…………….
Soluble salt solution (B)	Soluble salt	…………….
Carbonate/ bicarbonate + Acid (dil)	Salt + ………. + …………	Decomposition of carbonate
Chlorides/nitrates + Acid (conc)	…………. + …………	Decomposition of chlorides and nitrates

Ans: Completed table along with the equations is given below:

Reactants	Products	Method
Soluble base + Acid (dil)	Salt + water	Neutralisation Titration
Metal + Non-metal	Salt (soluble/insoluble)	Direct Combination
Insoluble base +	Salt (soluble) + water	…………….
Active metal + Acid (dil)	Salt + Hydrogen	Displacement
Soluble salt solution (A) + Soluble salt solution (B)	Precipitated salt + Soluble salt	Precipitation
Carbonate /bicarbonate + Acid (dil)	Salt + Water+ Carbon dioxide	Decomposition of carbonate
Chlorides/nitrates + Acid (conc)	Acid salt + HCl/HNO3	Decomposition of chlorides and nitrates

 

Que-13: Write the balanced equation for the preparation of the following salts in the laboratory:

(a) A soluble sulphate by the action of an acid on an insoluble base,
(b) An insoluble salt by the action of an acid on another salt,
(c) An insoluble base by the action of a soluble base on a soluble salt
(d) A soluble sulphate by the action of an acid on a metal.

Ans:
(a) CuO + H₂SO₄ ⟶ CuSO₄ + H₂O
(b) AgNO₃ + HCl ⟶ AgCl ↓ + HNO₃
(c) FeCl₃ + 3NaOH [base] ⟶ 3NaCl + Fe(OH)₃ ↓
(d) Zn + H₂SO₄ ⟶ ZnSO₄ + H₂↑

Que-14: You are provided with the following chemicals:

NaOH,Na₂CO₃,H₂O,Zn(OH)₂,CO₂,HCl,Fe,H₂SO₄,Cl₂,Zn
Using suitable chemicals from the given list only, state briefly how you would prepare:
(a) Iron(III) chloride,
(b) Sodium sulphate,
(c) Sodium zincate,
(d) Iron(II) sulphate,
(e) Sodium chloride.

Ans: (a) Iron (III) Chloride: By synthesis i.e., direct combination of elements.
2Fe + 3Cl₂ ⟶ 2FeCl₂
(b) Sodium sulphate: By neutralisation of an alkali (caustic soda) with acid (dilute sulphuric acid)
2NaOH + H₂SO₄ ⟶ Na₂SO₄ + 2H₂O
(c) Sodium zincate: By the action of metals with alkalis
Zn + 2NaOH ⟶ Na₂ZnO₂ + H₂
(d) Iron (II) sulphate: Method of Simple Displacement by the action of dilute acid (H₂SO₄) on an active metal (iron).
Fe + H₂SO₄ (dil.) ⟶ FeSO₄ + H₂
(e) Sodium chloride: By the neutralisation reaction of strong acid (HCl) with strong base (NaOH) also known as titration NaOH + HCl ⟶ NaCl + H₂O

Que-15: For each of the salt: A, B, C and D, suggest a suitable method of its preparation.

(a) A is a sodium salt.
(b) B is an insoluble salt.
(c) C is a soluble salt of copper.
(d) D is a soluble salt of zinc.

Ans:
(a) By neutralisation:
NaOH + HCl → NaCl + H₂O
(b) By precipitation:
Pb(NO₃)₂ + 2NaCl → PbCl₂ + 2NaNO₃
(c) CuCO₃+ H₂SO₄→ CuSO₄ + H₂O + CO₂
(d) Simple displacement:
Zn + H₂SO₄→ ZnSO₄ + H₂

Que-16: Choosing only substances from the list given in the box below, write equations for the reactions which you would use in the laboratory to obtain:

(a) Sodium sulphate
(b) Copper sulphate
(c) Iron(II)sulphate
(d) Zinc carbonate

Dilute sulphuric acid	Copper	Copper carbonate
	Iron	Sodium carbonate
	Sodium
	Zinc

Ans:

(a) Na₂CO₃ + H₂SO₄ (dil.) ⟶ Na₂SO₄ + H₂O + CO₂↑
(b) CuCO₃ + H₂SO₄ (dil.) ⟶ CuSO₄ + H₂O + CO₂↑
(c) Fe + H₂SO₄ (dil.) ⟶ FeSO₄ + H₂↑
(d) Zn + H₂SO₄ (dil.) ⟶ ZnSO₄ + H₂↑
ZnSO₄ + Na₂CO₃ ⟶ ZnCO₃ + Na₂SO₄

Que-17: From the formula listed below, choose one, in each case, corresponding to the salt having the given description: AgCl, CuCO₃, CuSO₄.5H₂O, KNO₃, NaCl, NaHSO₄, Pb(NO₃)₂, ZnCO₃, ZnSO₄.7H₂O.

(a) an acid salt
(b) an insoluble chloride
(c) on treating with concentrated sulphuric acid, this salt changes from blue to white
(d) on heating, this salt changes from green to black
(e) this salt gives nitrogen dioxide on heating

Ans:
(a) NaHSO₄
(b) AgCl
(c) CuSO₄.5H₂O
(d) CuCO₃
(e) Pb(NO₃)₂

Que-18:

(a) Ca(H₂PO₄)₂is an example of a compound called _______ (acid salt/basic salt/normal salt).
(b) Write the balanced equation for the reaction of: A named acid and a named alkali.

Ans:
(a) acid salt
(b) NaOH+ HCl → NaCl + H₂O

Que-19: State the terms defined by the following sentences:

(a) A soluble base.
(b) The insoluble solid formed when two solutions are mixed together.
(c) An acidic solution in which there is only partial ionisation of the solute molecules.

Ans:
(a) Alkali
(b) Precipitate
(c) Weak acid

Que-20: Which of the following methods, A, B, C, D or E is generally used for preparing the chlorides listed below from (i) to (v). Answer by writing down the chloride and the letter pertaining to the corresponding method. Each letter is to be used only once.

A Action of an acid on a metal
B Action of an acid on an oxide or carbonate
C Direct combination
D Neutralisation of an alkali by an acid
E Precipitation (double decomposition)
(i) Copper (II) chloride
(ii) Iron (II) chloride
(iii). Iron (III) chloride
(iv) Lead (II) chloride
(v) Sodium chloride

Ans:
(i) Copper (II) chloride – B
(ii) Iron (II) chloride – A
(iii). Iron (III) chloride – C
(iv) Lead (II) chloride – E
(v) Sodium chloride – D

Que-21: From the list given below, which one is:

[SO₂, SiO₂, Al₂O₃, CO, MgO, Na₂O]
(a) A covalent oxide of a metalloid
(b) An oxide which when dissolved in water form acid.
(c) A basic oxide
(d) An amphoteric oxide

Ans:
(a) Silicon is a metalloid. The covalent oxide is SiO_​2
(b) Acidic oxide – gives acid with water – SO₂
SO₂ + H₂O —-> H₂SO₃
(c) Basic oxide – gives base with water – Na₂O
Na₂O + H₂O —–> 2 NaOH
(d) An amphoteric oxide – Shows both acidic and basic property
Al₂O₃

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