Class 10 SELINA Solutions Chemistry Chapter 3 - Acids, Bases and Salts

(a) Acids are defined as compounds which contain one or more hydrogen atoms, and when dissolved in water, they produce hydronium ions (H₃O⁺), the only positively charged ions.

(b) Hydronium ion

(c) H₃O⁺

H₂SO₄ + H₂O ⇌ H₃O⁺ + HSO₄^- 

HSO₄^- + H₂O ⇌ H₃O⁺ + SO₄^-2

If water is added to a concentrated acid, the heat generated causes the mixture to splash out and cause severe burns. Thus, water is never added to acid in order to dilute it.

Basicity: The basicity of an acid is defined as the number of hydronium ions (H₃O⁺) that can be produced by the ionization of one molecule of that acid in aqueous solution.

The basicity of following compounds are:

Nitric acid:Basicity= 1

Sulphuric acid: Basicity=2

Phosphoric acid: Basicity=3

(a) Oxyacids: - HNO₃, H₂SO₄

(b) Hydracid:- HCl, HBr

(c) Tribasic acid:- H₃PO₄, H₃PO₃

(d) Dibasic acid: - H₂SO₄ , H₂CO₃

(a) The anhydride of following acids are:

(i) Sulphurous acid: SO₂

(ii) Nitric acid: N₂O₅

(iii) Phosphoric acid: P₂O₅

(iv) Carbonic acid: CO₂

(b) Acids present in following are:

Vinegar: Acetic acid

Grapes: Tartaric acid and Malic acid

Lemon: Citric acid

Acetic acid is a monobasic acid which on ionization in water produce one hydronium ion per molecule of the acid.

(i) 2NO_2(g) + H₂O_(l)→ HNO_2(aq) + HNO₃

(ii) H₂S₂O₇ + H₂O  → 2 H₂SO₄

The strength of an acid is the extent to which the acid ionizes or dissociates in water.

The strength of an acid depends on the degree of ionization and concentration of hydronium ions [H₃O⁺] produced by that acid in aqueous solution.

(a)Carbonic acid is a dibasic acid with two replaceable hydrogen ions; therefore it forms one acid salt or one normal salt.

Hydrochloric acid is a monobasic acid with one replaceable hydrogen ion and so forms only one normal salt.

(b) Strength of an acid is the measure of concentration of hydronium ions it produces in its aqueous solution. Dil. HCl produces high concentration of hydronium ion compared to that of concentrated acetic acid. Thus, dil. HCl is stronger acid than highly concentrated acetic acid.

(c) H₃PO₃ is not a tribasic acid because in oxyacids of phosphorus, hydrogen atoms which are attached to oxygen atoms are replaceable. Hydrogen atoms directly bonded to phosphorus atoms are not replaceable.

(d) The salt produced is insoluble in the solution so the reaction does not proceed. Hence, we do not expect lead carbonate to react with hydrochloric acid.

(e) NO₂ is called double acid anhydride because two acids – nitrous acid and nitric acid – are formed when it reacts with water.

2NO₂ + H₂O → HNO₂ + HNO₃

 (a) Acids are prepared from non-metals by their oxidation. For example :

Sulphur or phosphorus is oxidized by conc. Nitric acid to form sulphuric acid or phosphoric acid.

(b) Acids are prepared from salt by the displacement reaction. For example :

Nitric acid is prepared by using H₂SO₄ and sodium chloride.

(a) SO₂ +H₂O H₂SO₃

(b) P₂O₅ +3H₂O 2H₃PO₄

(c) CO₂ + H₂O H₂CO₃

(d)

(a) Citric acid

(b) Carbonic acid

(c) Oxalic acid

(d) Boric acid

(a) Chlorides react with concentrated sulphuric acid on warming to liberate hydrogen chloride.

(b) Nitrates when heated with conc. sulphuric acidproduce more volatile nitric acid.

 Both chlorides and nitrates do not react with dilute acids; they react with concentrated acids.

An alkali is a basic hydroxide which when dissolved in water produces hydroxyl ions (OH^-) as the only negatively charged ions.

(a) Strong alkalis: Sodium hydroxide , Potassium hydroxide

(b) Weak alkalis: Calcium hydroxide , Ammonium hydroxide

(a) An alkali and a base:

1. Alkalis are soluble in water whereas bases may be or may not be soluble in water.

2. All alkalis are bases but all bases are not alkalis.

(b) The chemical nature of an aqueous solution of HCl and an aqueous solution of NH₃

1. The aqueous solution of HCl is acidic in nature. It can turn blue litmus to red.

2. The aqueous solution of NH₃ is basic in nature. It can turn red litmus to blue.

a. Hydroxyl ion (OH^-)

b. H⁺

(a) Barium oxide

(b) Sodium hydroxide

(c) Manganese oxide

(d) Cupper hydroxide

(e) Carbonic acid

(f) Ferric hydroxide

(g) Copper oxide

(h) Ammonia

(i) Ammonium hydroxide

The test tube containing distilled water does not affect the red litmus paper.

The test tube containing acidic solution does not change the red litmus paper.

But the test tube containing basic solution turns red litmus paper blue.

It is because HCl and HNO₃ ionize in aqueous solution whereas ethanol and glucose do not ionize in aqueous solution.

a. Dry HCl gas does not contain any hydrogen ions in it, so it does not show acidic behaviour. Hence, dry HCl gas does not change the colour of dry litmus paper.

b. Lead oxide is a metallic oxide which reacts with hydrochloric acid to produce lead chloride and water, but it is excluded from the class of bases, because chlorine is also produced.

 PbO₂ + 4HCl → PbCl₂ + Cl₂ + 2H₂O

 Thus, lead oxide is not a base.

c. Yes, basic solutions have H⁺ ions, but the concentration of OH^- ions is more than the H⁺ ions which makes the solution basic in nature.

(a) We can obtain a base from another base by double decomposition. The aqueous solution of salts with base precipitates the respective metallic hydroxide.   

FeCl₃ +3NaOH Fe(OH)₃ +3NaCl

(b) An alkali from a base

_(c) Salt from another salt

(a) Mg +2HCl MgCl₂ + H₂

(b) HCl + NaOH NaCl + H₂O

(c) CaCO₃ +2HCl CaCl₂ +H₂O + CO₂

(d) CaSO₃ + 2HCl CaCl₂ + H₂O+ SO₂

(e) ZnS + 2HCl ZnCl₂ + H₂S

As we know that alkalis react with oil to form soap. As our skin contains oil so when we touch strong alkalis, a reaction takes place and soapy solution is formed. Hence we should wear gloves.

pH represents the strength of acids and alkalis expressed in terms of hydrogen ion concentration.

The solution with pH value 10 will give pink colour with phenolphthalein indicator.

A = Strongly acidic

B= neutral

C=Weakly alkaline

D= Strongly alkaline

E= Weakly acidic

(a) Solution A (acidic solution) + MgH₂ + Mg salt

(b) SolutionA (acidic solution) + ZnH₂ + Zn salt

(a) A common acid-base indicator and a universal indicator:

An acid-base indicator like litmus tells us only whether a given substance is an acid or a base. The universal indicator gives an idea as to how acidic or basic a substance is universal indicator gives different colours with solutions of different pH values.

(b) The acidity of bases and basicity of acids

The acidity of bases: The number of hydroxyl ions which can be produced per molecule of the base in aqueous solution.

Basicity of acid: The basicity of an acid is defined as the number of hydronium ions that can be produced by the ionization of one molecule of that acid in aqueous solution.

(c) Acid and alkali:

An acid is that substance which gives H⁺ ions when dissolved in water. 

An alkali is that substance which gives OH^- ions when dissolved in water.

(a) Alkali

(b) Acid

Substances like chocolates and sweets are degraded by bacteria present in our mouth. When the pH falls to 5.5 tooth decay starts. Tooth enamel is the hardest substance in our body and it gets corroded. The saliva produced by salivary glands is slightly alkaline, it helps to increase the pH, to some extent, but toothpaste which contains basic substance is used to neutralize excess acid in the mouth.

A universal indicator is a mixture of dyes which identify a gradual change of various colours over a wide range of pH, depending on the strength of the acid. When we use a universal indicator, we see solutions of different acids produce different colours. Indeed, solutions of the same acid with different concentration give different colours.

The more acidic solutions turn universal indicator bright red. A less acidic solution will only turn it orange-yellow. Colour differences can also be observed in case of vinegar which is less acidic and battery acid which is more acidic.

a.  

i. The pH can be increased by adding a basic solution.

ii. The pH can be increased by adding an acidic solution.

b. The solution is basic in nature and the pH value will be more than 7.

c. Less than 7

a. Solution P

b. Solution R

c. Solution Q

(a) blue

(b) red

(c) hydrogen gas

(d) basic, alkaline

(e) graphite

(a) A normal salt: Normal salts are the salts formed by the complete replacement of the ionisable 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 ionisable hydrogen atoms of a polybasic acid by a metal or an ammonium ion.

(c) A basic salt: Basic salts are formed by the partial replacement of the hydroxyl group of a di- or tri- acidic base by an acid radical.

Examples:

(a) A Normal salt: Na₂SO₄, NaCl

(b) An acid salt: NaHSO₄, Na₂HPO₄

(c) A basic salt: [Pb(OH)Cl], [Mg(OH)Cl].

(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

(a) Direct combination

When two substance reacts chemically to form a new substance which is a compound it is a direct combination reaction. This reaction is also termed as synthesis.

This reaction taken place when two elements are heated together.

Metal + Non metal → Salt

For example,

2Na(molten) + Cl₂ → 2NaCl

(b) Displacement:

Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound.

For example,

Action of dilute acids on active metals. Soluble salts of active metals are prepared by this method.

Active metal + Acid (dil.) → Salt + Hydrogen

Zn + H₂SO₄ → ZnSO₄ + H₂↑

(c) Double decomposition (precipitation):

It is a chemical change, in which two compounds in solution react to form two other compounds by the mutual exchange of radicals. A solid precipitate is formed as a result of the reaction.

For example,

Barium is more reactive than hydrogen, hence it displaces hydrogen from its compound H₂SO₄ in aqueous solution to form barium sulphate precipitate. Hence, this reaction is also called as precipitation reaction. The chemical reaction is as follows:

BaCl₂ + H₂SO₄BaSO₄ + 2HCl

(d) Neutralisation of insoluble base:

Acid + Insoluble base → Salt + Water

Preparation of copper (II) sulphate (or blue vitriol)

By the action of dilute acid (dil. H₂SO₄) on an insoluble base copper hydroxide, copper oxide or copper carbonate.

For example,

Cu(OH)₂ + H₂SO₄ → CuSO₄ + 2H₂O

(e) Neutralisation of an alkali (also called as titration):

Acid + Soluble base → Salt + Water

For example,

Neutralisation of caustic soda with dilute sulphuric acid.

Reaction:

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

This method is useful for preparing the soluble salts of only sodium, potassium and ammonium. Since, the reactants as well as the products are soluble, a titration is conducted to determine the completion of the neutralization reactions.

(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

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 +2HCl PbCl₂ +2HNO₃

3.Sodium sulphate: - D( Titration of dilute acid with a solution of soluble base)

2NaOH + H₂SO₄ Na₂SO₄ +2H₂O

4. Copper sulphate:- C (reaction of dilute acid with an insoluble base)

Cu(OH)₂ +H₂SO₄ CuSO₄ + 2H₂O

(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

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 contains hydroxide ions. A base reacts with an acid to form a salt and water only. This type of reaction is known as neutralisation.

(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.

(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.

Zinc Sulphate - Displacement

Ferrous sulphide - synthesis

Barium sulphate - Precipitation

Ferric Sulphate- Oxidation

Sodium sulphate - Neutralisation

(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.

_(a)

_(b)

(c)

_(d)

(a) Iron (III) Chloride: Iron chloride is formed by direct combination of elements.

_(b) Sodium sulphate: By neutralization of caustic soda with dilute sulphuric acid

_(c) Sodium zincate: By the action of metals with alkalis

_(d) Iron (II) sulphate: Iron sulphate is prepared by the action of dilute acid on an active metal.

_(e) Sodium chloride: By the neutralization reaction of strong acid with strong base

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

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

a. NaHSO₄

b. AgCl

c. CuSO₄.5H₂O

d. CuCO₃

e. Pb(NO₃)₂

a. acid salt

b. NaOH + HCl → NaCl + H₂O

a. Alkali

b. Precipitate

c. Weak acid

i. Copper (II) chloride - B

ii. Iron (II) chloride - A

iii. Iron (III) chloride - C

iv. Lead (II) chloride - E

v. Sodium chloride - D

1. A covalent oxide of a metalloid - SiO₂
2. An oxide which when dissolved in water from acid- SO₂
3. A basic oxide- Na₂O, MgO
4. An amphoteric oxide- Al₂O₃

It is the amount of water molecules which enter into loose chemical combination with one molecule of the substance on crystallisation from its aqueous solution.

a. Crystalline hydrated salts which on exposure to the atmosphere lose their water of crystallisation partly or completely and change into a powder. This phenomenon is called efflorescent and the salts are called efflorescent.

Examples: CuSO₄.5H₂O, MgSO₄.7H₂O, Na₂CO₃.10H₂O

b. Water-soluble salts which on exposure to the atmosphere absorb moisture from the atmosphere and dissolve in the same and change into a solution. The phenomenon is called deliquescence and the salts are called deliquescent.

Examples: CaCl₂, MgCl₂, ZnCl₂

a. Water of crystallization

b. White

c. By heating with any dehydrating agent

d. A deliquescent salt – Calcium chloride, zinc chloride

e. Hydrated copper sulphate turns white on heating because, it loses water of crystallisation.

(a) When washing soda (Na₂CO₃.10H₂O) is exposed to air, it loses 9 molecules of water to form a monohydrate.

(b) It absorbs moisture from the atmosphere and becomes moist and ultimately dissolves in the absorbed water, forming a saturated solution.

a. Sodium hydrogen sulphate [NaHSO₄] is an acid salt and is formed by the partial replacement of the replaceable hydrogen ion in a dibasic acid [H₂SO₄]. The [H] atom in NaHSO₄ makes it behave like an acid.

 So, on dissolving in water, it gives hydrogen ions.

b. Desiccating agents are used to absorb moisture. Anhydrous calcium chloride (CaCl₂) has the capacity of absorbing moisture as it is hygroscopic in nature. So, it is used in a desiccator.

Conc. sulphuric acid is hygroscopic in nature and can remove moisture from other substances; therefore, it is used as a drying agent.

It is also used as a dehydrating agent because it has a strong affinity for water and thus absorbs water quickly from compounds.

a. Increase

b. Increase

c. Decrease

d. Increase

e. Increase

a. Table salt turns moist and ultimately forms a solution on exposure to air especially during the rainy season. Although pure sodium chloride is not deliquescent, the commercial version of the salt contains impurities (such as magnesium chloride) which are deliquescent substances.

b. The impurity can be removed by passing a current of dry hydrogen chloride gas through a saturated solution of the affected salt. Pure sodium chloride is produced as a precipitate which can be recovered by filtering and washing first with a little water and finally with alcohol.

c. Conc. sulphuric acid

d. Common salt and sugar

(a) Iron chloride(FeCl₃)

      FeCl₃ + 3H₂O → 3HCl + Fe(OH)₃

(b) Ammonium acetate (CH₃COONH₄)

      CH₃COONH₄ +H₂O → CH₃COOH + NH₄OH

(c) Sodium chloride

       NaCl_(s) + H₂O → Na⁺_(aq)  OH^-_(aq) + H₂O

(a) Na₂CO₃ solution: This solution is alkaline in nature; hence, red litmus changes to blue.

(b) NaCl solution: There is no change in the colour of the litmus paper because this solution is neutral.

(c) NH₄NO₃: This solution is alkaline in nature; hence, red litmus changes to blue.

(d) MgCl₂: It is slightly acidic and neutral; hence, there is no change in the litmus paper. 

(a) Fe + 2HCl (dil) FeCl₂ + H₂

(bi) 2Fe (heated) + 3Cl₂ (dry) 2FeCl₃

(c) Fe + H₂SO₄ (dil) FeSO₄ + H₂

(d) Fe + S FeS

A = HCl

B = Na₂CO₃

C = HNO₃

D = NaOH

A: Fe + 2HCl → FeCl₂ + H₂

B: FeCl₂ + Zn→ ZnCl₂ + Fe

Fe + H₂CO₃ → FeCO₃ + H₂↑ 

C: FeCO₃ + 2HNO₃ → Fe (NO₃)₂ + H₂O + CO₂

D: Fe(NO₃)₂ + 2NaOH → Fe(OH)₂ + 2NaNO₃

(a) The first step is to convert insoluble lead carbonate into soluble lead nitrate by treating lead carbonate with dilute nitric acid.

(b) PbCO₃ (s) + 2HNO₃(dil) Pb(NO₃)₂ (aq) + H₂O (l) + CO₂

(c) When dilute sulphuric acid is added directly to lead carbonate, the lead sulphate thus formed will be deposited on solid lead carbonate disconnecting lead carbonate from sulphuric acid.

(i) Complex salts

(ii) Alkali

(i)

(ii)

(iii)

(iv)

a. (iv) Acetic acid

b. (iv) Copper (II) oxide

c.  

 (i) Solution B 

 (ii) Solution C 

 (iii) Ammonium hydroxide solution

d.  

e. A neutralisation reaction is when an acid and a base react to form water and a salt, and involves the combination of H⁺ ions and OH^- ions to generate water.

f.  

 i. B is an anhydrous calcium chloride.

 ii. B absorbs moisture from the receiver.

 iii. Because iron (III) chloride is highly deliquescent and it absorbs moisture from the surrounding air to form a saturated solution.

 iv. 

a. A (ii) 

 B (iv)

 C (v)

b. (i) A

 (ii) D

c.  

 i. 

 ii. 

 iii. 

 iv. 

d.  

 i. 

 ii. 

 iii. 

 iv. 

a. Pb(NO₃)₂ + 2NaCl → PbCl₂ + 2NaNO₃

b. When crystals of washing soda are exposed to air, it loses its water of crystallisation and the phenomenon is known as efflorescence.

c. 

 i. (B) Neutralisation

 ii. (E) Direct synthesis

 iii. (D) Double decomposition

 iv. (A) Simple displacement

 v. (C) Decomposition by acid

a. 1→C

 2→A

 3→E

 4→B

 5→D

(b) Zinc granule is added to copper sulphate  solution:

When zinc granules are added to the solution of copper sulphate, zinc displaces copper to form zinc sulphate and thus copper gets deposited. In this reaction, zinc metal can easily displace the copper metal from its salt to form an aqueous solution of zinc sulphate. This is an example of displacement reaction.

Zn(s) + CuSO₄ (aq) → ZnSO₄ (aq) + Cu↓

(c) Silver nitrate solution with sodium chloride solution:

When Silver nitrate (AgNO₃) is mixed with the solution of Sodium chloride (NaCl) then the ions of both the compounds get exchanged. As a result, white precipitates of Silver chloride is formed (AgCl) and the solution of Sodium nitrate (NaNO₃) are formed. This is an example of double displacement reaction.

AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃

a.  

 i. Hydronium 

 ii. Hydroxide

 iii. Salt

 iv. Water

 v. Hydrogen

b.  

 i. Acidic salt

 ii. Water of crystallisation

 iii. Deliquescence

c. 

Chemical equations:

 i. Sodium sulphate:

 2Na + H₂SO₄ (dil.) → Na₂SO₄ + H₂↑ 

 ii. Zinc carbonate:

 Zn(NO₃)₂ + CuCO₃→ ZnCO₃ + Cu(NO₃)₂

 iii. Copper (II) sulphate:

 CuCO₃ + H₂SO₄ (dil.) → CuSO₄ + H₂O + CO₂

 iv. Iron (II) sulphate:

 Fe + H₂SO₄ (dil.) → FeSO₄ + H₂↑

Correct option: (i) CO

From all these gases only carbon monoxide does not react with water to form an acid.

a. 1

b. The stable positive ion formed when an acid dissolves in water is hydronium ion. The structure of hydronium ion (H₃O⁺) is as follows:

c. Salt S is prepared by reacting dilute sulphuric acid with copper oxide. Hence, salt S is copper sulphate.

d.  

 i. Lead sulphate from lead carbonate

 ii. Sodium sulphate using dilute sulphuric acid Dilute sulphuric acid neutralises bases (oxides and hydroxides) to form salts and water.

 iii. Copper chloride using copper carbonate

(a)  

(b) SO₂ is an acidic oxide which dissolves in water forming an acid.