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Acids, Bases and Salts Solutions - Chemistry Class 10 ICSE - Acids, Bases and Salts | Chemistry Class 10 ICSE | Bright Tutorials

Acids, Bases and Salts

Solutions for Chemistry, Class 10, ICSE

Exercise 3A

20 questions

Question 1

What do you understand by an alkali? Give two examples of :

(a) strong alkalis

(b) weak alkalis

Exercise 3A

Answer:

An alkali is a base soluble in water. All alkalis form hydroxyl (OH^-) ions in aqueous solution as the only negative ions. They turn red litmus blue.

(a) Strong alkalis — Sodium hydroxide [NaOH], Potassium hydroxide [KOH]

(b) Weak alkalis — Calcium hydroxide [Ca(OH)₂], Ammonium hydroxide [NH₄OH]

Question 2

What is the difference between :

(a) an alkali and a base,

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

Exercise 3A

Answer:

(a) Difference between an alkali and a base:

Alkali	Base
An alkali is a compound which when dissolved in water yields hydroxyl ions [OH^-] as the only negatively charged ions.	A base is either a metallic oxide or a metallic hydroxide or ammonium hydroxide which reacts with hydronium ions of an acid to form salt and water only.
Alkalis are soluble in water	Bases may be or may not be soluble in water.
All alkalis are bases	All bases are not alkalis.

(b) Difference between chemical nature of an aq. soln. of HCl and NH₃:

Chemical nature of an aq. soln. of HCl	Chemical nature of an aq. soln. of NH₃
The aqueous soln. of HCl is acidic in nature.	The aqueous soln. of NH₃ is basic in nature.
It can turn blue litmus to red.	It can turn red litmus to blue.
It gives hydronium ions in the solution	It gives hydroxyl ions in the solution.

Question 3

Name the ions furnished by:

(a) bases in solution

(b) an acid

Exercise 3A

Answer:

(a) bases in solution — Hydroxyl ion [OH^-]

(b) an acid — H₃O[⁺] . At first the the hydrogen molecule furnishes hydrogen ion, but this hydrogen ion cannot exist independently. Therefore it combines with water molecule to form hydronium ion H₃O[⁺].

Question 4

Give one example in case:

(a) A basic oxide which is soluble in water,

(b) A hydroxide which is highly soluble in water,

(d) A hydroxide which is insoluble in water,

(e) A weak mineral acid

(f) A base which is not an alkali

(g) An oxide which is a base,

(h) A hydrogen containing compound which is not an acid

(i) A base which does not contain a metal ion.

Exercise 3A

Answer:

(a) Sodium oxide [Na₂O]

(b) Sodium hydroxide [NaOH]

(d) Aluminium hydroxide [Al(OH)₃]

(e) Carbonic acid [H₂CO₃]

(f) Ferric hydroxide [Fe(OH)₃]

(g) Copper (II) oxide [CuO]

(h) Ammonia [NH₃]

(i) Ammonium hydroxide [NH₄OH]

Question 5

You have been provided with three test tubes. One of them contains distilled water and the other two have an acidic solution and a basic solution respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?

Exercise 3A

Answer:

We take three pieces of red litmus paper. The solution which turns red litmus paper to blue is basic solution. Distilled water (neutral) and acidic solution will not effect red litmus paper.

Now we divide the so formed blue litmus paper into two pieces. The test tube containing distilled water does not change the colour of the blue litmus paper.

The test tube containing acidic solution changes the colour of the blue litmus paper to red. Hence, we can identify the three solutions.

Question 6

HCl, HNO₃, C₂H₅OH, C₆H₁₂O₆ all contain H atoms but only HCl and HNO₃ show acidic character. Why?

Exercise 3A

Answer:

HCl and HNO₃ show acidic character because they ionise in aqueous solution.

Ionisation of HCl in water:

HCl ⟶ H⁺ + Cl^-

H⁺ + H₂O ⟶ H₃O⁺

Ionisation of HNO₃ in water:

HNO₃ ⟶ H⁺ + NO₃^-

H⁺ + H₂O ⟶ H₃O⁺

C₂H₅OH (Ethanol) and C₆H₁₂O₆ (Glucose) are covalent compounds. Their H atoms do not ionise in water to form hydronium ions [H₃O⁺]. Hence, they don't show acidic character.

Question 7

(a) Dry HCl gas does not change the colour of dry litmus paper. Why?

(b) Is PbO₂ a base or not? Comment.

Exercise 3A

Answer:

(a) The colour of litmus paper changes only in presence of ions like hydrogen [H⁺] or hydronium ions [H₃O⁺]. HCl can produce these ions only in the form of aqueous solution. Hence, dry HCl gas does not change the colour of dry litmus paper.

(b) A base reacts with an acid to form salt and water ONLY. The word ONLY is of importance in the definition of a base. Lead oxide reacts with hydrochloric acid to produce lead (II) chloride (a salt) and water, but the word "only" excludes it from the class of bases because chlorine is also produced.

PbO₂(s) + 4HCl(aq.) ⟶ PbCl₂(aq.) + Cl₂(g) + 2H₂O

Thus, PbO₂ 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.

Example — Sodium hydroxide (NaOH). It has more OH^- ions than H⁺ ions, so it is basic in nature.

Question 8

How would you obtain:

(a) a base from another base,

(b) an alkali from a base,

Exercise 3A

Answer:

(a) A base from another base can obtained by double decomposition. The aqueous solution of salts with base (alkali) precipitates the respective metallic hydroxide.
For example,

FeCl₃ + 3NaOH ⟶ 3NaCl + Fe(OH)₃ ↓ [red brown ppt.]

(b) An alkali from a base can be obtained by the action of water on soluble metallic oxides like oxides of sodium, potassium and calcium:

CaO + H₂O ⟶ Ca(OH)₂

(c) A salt from another salt can be obtained by adding an alkali to the solutions of the salts of the heavy metals like copper, iron, zinc, etc.
For example,

FeSO₄ [aq.] + 2NaOH [aq.] ⟶ Na₂SO₄ [aq.] + Fe(OH)₂ ↓ [dirty green]

Question 9

Write balanced equation to satisfy each statement.

(a) Acid + Active metal ⟶ Salt + Hydrogen

(b) Acid + Base ⟶ Salt + Water

(d) Acid + sulphite or bisulphite ⟶ Salt + water + sulphur dioxide

(e) Acid + sulphide ⟶ Salt + hydrogen sulphide

Exercise 3A

Answer:

(a) Mg + 2HCl ⟶ MgCl₂ + H₂

(b) HCl + NaOH ⟶ NaCl + H₂O

(d) CaSO₃ + 2HCl ⟶ CaCl₂ + H₂O + SO₂

(e) ZnS + 2HCl ⟶ ZnCl₂ + H₂S

Question 10

The skin has and needs natural oils. Why it is advisable to wear gloves while working with strong alkalis?

Exercise 3A

Answer:

Alkalis react with oil to form soap. Since, our skin contains oil hence when we touch strong alkalis, a reaction takes place and soapy solutions are formed. This reaction can be corrosive for skin. Hence we should wear gloves while working with strong alkalis.

Question 11

Complete the table:

Indicator	Neutral	Acidic	Alkaline
Litmus	Purple	..........	..........
Phenolphthalein	Colourless	..........	..........

Exercise 3A

Answer:

Completed table is shown below:

Indicator	Neutral	Acidic	Alkaline
Litmus	Purple	*blue to red*	*red to blue*
Phenolphthalein	Colourless	*colourless*	*pink*

Question 12

What do you understand by pH value? Two solution X and Y have pH values of 4 and 10 respectively. Which one of these two will give a pink colour with phenolphthalein indicator.

Exercise 3A

Answer:

pH of a solution is the negative logarithm to the base 10 of the hydrogen ion concentration expressed in moles per litre.

The solution with pH value 10 [i.e., Y] will give pink colour with phenolphthalein indicator.

Question 13

M is an element in the form of powder. M burns in oxygen and the product obtained is soluble in water. The solution is tested with litmus. Write down only the word which will correctly complete each of the following sentences.

(a) If M is a metal, then the litmus will turn ...............

(b) If M is a non-metal, then the litmus will turn ...............

(d) If M is a metal, it will form ............... oxide, which will form ............... solution with water.

(e) If M is a non-metal, it will not conduct electricity unless it is in the form of ...............

Exercise 3A

Answer:

(a) If M is a metal, then the litmus will turn blue

(b) If M is a non-metal, then the litmus will turn red

(d) If M is a metal, it will form basic oxide, which will form alkaline solution with water.

(e) If M is a non-metal, it will not conduct electricity unless it is in the form of graphite.

Explanation:

(a) Metal, M burns in oxygen to form an oxide. Metallic oxide forms an alkaline solution in water. Hence, turns red litmus blue.

(b) A non-metal on reacting with oxygen produces an acidic oxide. This acidic oxide will turn blue litmus paper blue.

(d) Metals react with oxygen to form basic oxide which dissolve in water to give alkaline solution.

(e) In Graphite, each carbon atom is bonded to three other carbon atoms. Thus, one electron of carbon remains free. Due to this free valence electron, graphite is a good conductor of electricity. All other non-metals are poor conductors of electricity.

Question 14

Distinguish between :

(a) a common acid base indicator and a universal indicator.

(b) acidity of bases and basicity of acids,

Exercise 3A

Answer:

(a) Difference between a common acid base indicator and a universal indicator:

Common acid-base indicator	Universal indicator
Common acid-base indicators test whether a solution is acidic, basic or neutral.	Universal indicator gives a spectrum of colours depending upon how acidic or alkaline a solution is.
Common acid-base indicators does not give the exact pH value of the solution.	Universal indicator helps to get a reasonably accurate pH value.

(b) Difference between acidity of bases and basicity of acids:

Acidity of bases	Basicity of acids
The acidity of bases is the number of hydroxyl ions [OH^-] which can be produced per molecule of the base in aqueous solution.	The basicity of an acid is defined as the number of hydronium ions [H₃O⁺] that can be produced by the ionisation of one molecule of that acid in aqueous solution.
On the basis of their acidity, bases are classified as Monoacidic base, Diacidic base and Triacidic base.	On the basis of their basicity, acids are classified as Monobasic acids, Dibasic acids and Tribasic acids.

Acid	Alkali
Acids are compounds which contain one or more hydrogen atoms and when dissolved in water, produce hydronium ions [H₃O⁺] as the only positively charged ions.	An alkali is a basic hydroxide which when dissolved in water produces hydroxyl [OH^-] ions as the only negatively charged ions.
Acids have a sour taste.	Alkalis have a sharp and bitter taste.
Acids have pH value less than 7.	Alkalis have pH value greater than 7.

Question 15

What should be added to neutral solution in order to :

(a) increase the concentration of hydronium ions,

(b) decrease the concentration of hydronium ions

Exercise 3A

Answer:

(a) Acid

(b) Alkali

Question 16

How does tooth enamel get damaged? What should be done to prevent it?

Exercise 3A

Answer:

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.

Question 17

When you use a universal indicator, you see that solutions of different acids produce different colours. Indeed, solutions of the same acid with different concentrations will also give different colours. Why?

Exercise 3A

Answer:

Universal indicators give different colours at different concentrations of hydrogen ions in a solution. The hydrogen ion concentration differs for the same acid with different concentrations. Hence, the universal indicator gives different colours for the same acid with different concentrations.

Question 18

You are supplied with five solutions : A, B, C, D and E with pH values as follows:

A = 1.8, B = 7, C = 8.5, D = 13, and E = 5

Classify these solutions as neutral, slightly or strongly acidic and slightly or strongly alkaline.

Which solution would be most likely to liberate hydrogen with:

(a) magnesium powder

(b) powdered zinc metal.

Give a word equation for each reaction.

Exercise 3A

Answer:

A = Strongly acidic

B = neutral

C = slightly alkaline

D = Strongly alkaline

E = slightly acidic

(a) Solution A (acidic solution)

Solution A (acidic solution) + magnesium powder ⟶ Hydrogen + Mg salt

(b) Solution A (acidic solution)

Solution A (acidic solution) + powdered zinc metal ⟶ Hydrogen + Zn salt

Question 19

Solution P has a pH of 13, solution Q has a pH of 6 and solution R has a pH of 2.

Which solution:

(a) Will liberate ammonia from ammonium sulphate on heating.

(b) is a strong acid?

Exercise 3A

Answer:

(a) Solution P
Reason — When alkalis are warmed with an ammonia salt, ammonia gas is given out.

(b) Solution R
Reason — Number 2 on pH scale represents a strong acid.

(c) Solution Q
Reason — As Q with pH 6 is a weak acid and will not be able to completely dissociate into ions. Hence, will have molecules and ions both.

Question 20

Select the word/s given which are required to correctly complete the blanks —

[ammonia, ammonium carbonate, carbonate, carbon dioxide, hydrogen, hydronium, hydroxide, precipitate, salt, water]

(i) A solution M turns blue litmus red, so it must contain (1) ............... ions; another solution O turns red litmus blue and hence it must contain (2) ............... ions.

(ii) When solution M and O are mixed together, the products will be (3) ............... and (4) ...............

(iii) If a piece of magnesium was put into solution M, (5) ............... gas would be evolved.

Exercise 3A

Answer:

(ii) When solution M and O are mixed together, the product will be (3) salt and (4) water.

(iii) If a piece of magnesium was put into a solution M, (5) hydrogen gas would be evolved.

Exercise 3B

22 questions

Question 1

Define the following and give two examples in each case : (a) a normal salt, (b) an acid salt, (c) a basic salt.

Exercise 3B

Answer:

(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.
Examples — Sodium Sulphate [Na₂SO₄], Sodium Chloride [NaCl]

(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.
Examples — Sodium Hydrogen Sulphate [NaHSO₄], Disodium Hydrogen Phosphate [Na₂HPO₄]

(c) A basic salt — Basic salts are formed by the partial replacement of the hydroxyl group of a di- or a tri-acidic base by an acid radical.
Examples — Basic lead chloride [Pb(OH)Cl], Basic magnesium chloride [Mg(OH)Cl].

Question 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 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.

Exercise 3B

Answer:

(a) Salt is a compound formed by the partial or total replacement of the ionisable hydrogen atoms of an acid by a metallic ion or an ammonium ion.

(b) An insoluble salt can be prepared by precipitation.

(d) By neutralisation of alkali (caustic soda) with acid (dilute sulphuric acid):
2NaOH + H₂SO₄ ⟶ Na₂SO₄ + 2H₂O

Question 3

Explain the following methods with examples:

(a) Direct combination

(b) Displacement

(d) Neutralization of insoluble base

(e) Neutralization of an alkali (titration)

Exercise 3B

Answer:

(a) In direct combination, a metal and a non-metal are heated together to obtain the corresponding salt.

i.e., Metal + Non-Metal ⟶ Salt

Example:

Pb + S $\xrightarrow{\space\Delta\space}$ PbS

(b) The displacement method involves action of a dilute acid on active metal producing the corresponding salt with the liberation of Hydrogen gas.

i.e., Active metal + Acid ⟶ Salt + Hydrogen

Example :

Zn + H₂SO₄ ⟶ ZnSO₄ + H₂

(c) Double decomposition (precipitation) — 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.

Example:

Na₂SO₄ + BaCl₂ ⟶ BaSO₄↓ + 2NaCl

(d) Neutralization of insoluble base — By the action of dilute acid on an insoluble base.

Example:

CuO + H₂SO₄ ⟶ CuSO₄ + H₂O

(e) Neutralization of an alkali (titration) — By the action of dilute acid on an alkali (i.e., soluble base):

Example:

2NaOH + H₂SO₄ ⟶ Na₂SO₄ + H₂O

Question 4

How would you prepare :

(a) copper sulphate crystals from a mixture of charcoal and black copper oxide.

(b) zinc sulphate crystals from zinc dust (powdered zinc and zinc oxide),

(d) calcium sulphate from calcium carbonate.

Exercise 3B

Answer:

(a) Copper sulphate crystals from a mixture of charcoal and black copper oxide

Method of preparation: Neutralization of insoluble base

Reaction:
CuO + H₂SO₄ ⟶ CuSO₄ + H₂O
CuSO₄ + 5H₂O ⟶ CuSO₄.5H₂O (blue vitriol)

Procedure:

Take dilute sulphuric acid in a beaker and heat it on wire gauze.
Add black 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 bright blue crystals of copper (II) sulphate pentahydrate CuSO₄.5H₂O (blue vitriol) and dry the crystals.

(b) Zinc sulphate crystals from Zinc dust

Method of preparation: Displacement — By the action of dilute acid (dil. H₂SO₄) on an active metal (Zinc, Iron).

Reaction:
Zn(s) + H₂SO₄(aq) ⟶ ZnSO₄ + H₂↑
ZnSO₄ + 7H₂O ⟶ ZnSO₄.7H₂O (white vitriol)

Procedure:

Take dilute sulphuric acid in a beaker and heat it on a wire gauze. Add some granulated zinc pieces with constant stirring.
Effervescence take place because of the liberation of hydrogen gas.
Add zinc till the Zinc settles at the base of the beaker.
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 a filter paper. The white, needle-shaped crystals are of hydrated Zinc sulphate.

Method of preparation: By passing carbon dioxide gas into a cold solution of sodium carbonate.

Reaction:
Na₂CO₃ + CO₂ + H₂O ⟶ 2NaHCO₃

Procedure:

Dissolve 5 grams of anhydrous sodium carbonate in about 25 cm³ 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 the folds of filter paper.

(d) calcium sulphate from calcium carbonate.

Method of preparation: By Double Decomposition (precipitation)

Reaction:
CaCO₃ + 2HNO₃ ⟶ Ca(NO₃)₂ + H₂O + CO₂↑
Ca(NO₃)₂ + Na₂SO₄ ⟶ CaSO₄↓ + 2NaNO₃

Procedure:

First insoluble Calcium Carbonate [CaCO₃] is converted to soluble Calcium Nitrate [Ca(NO₃)₂] with the help of dilute nitric acid.
The resulting solution is then treated with Sodium Sulphate [Na₂SO₄] and a precipitate of Calcium Sulphate is obtained.

Question 5

The following is a list of methods for the preparation of salts:

A — direct combination of two elements

B — reaction of a dilute acid with a metal

C — reaction of a dilute acid with an insoluble base

D — titration of a dilute acid with a solution of soluble base.

E — reaction of two solutions of salts to form a precipitate.

Choose from the list A to E, the best method of preparing the following salts by giving a suitable equation in each case:

Anhydrous ferric chloride
Lead chloride
Sodium sulphate
Copper sulphate

Exercise 3B

Answer:

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

Question 6

Name:

(a) a chloride which is insoluble in cold water but dissolves in hot water,

(b) a chloride which is insoluble

(d) a basic salt,

(e) an acidic salt,

(f) a mixed salt,

(g) a complex salt,

(h) a double salt.

Exercise 3B

Answer:

(a) a chloride which is insoluble in cold water but dissolves in hot water - Lead Chloride [PbCl₂]

(b) a chloride which is insoluble - Silver chloride [AgCl]

(d) a basic salt - Basic lead chloride [Pb(OH)Cl]

(e) an acidic salt - Sodium hydrogen sulphate [NaHSO₄]

(f) a mixed salt - Sodium potassium carbonate [NaKCO₃]

(g) a complex salt - Sodium zincate [Na₂ZnO₂]

(h) a double salt - Dolomite [CaCO₃.MgCO₃]

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

Exercise 3B

Answer:

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 O₂^- ions. A base reacts with an acid to form a salt and water only. This type of reaction is known as neutralisation.

Question 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,

Exercise 3B

Answer:

(a) Blue litmus will turn into red showing acidic nature of solution.

(b) Red litmus will turn into blue showing alkaline nature of ammonia.

Question 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

Exercise 3B

Answer:

(a) Since sodium hydroxide and sulphuric acid both are soluble, an excess of either of them cannot be removed by filtration. Therefore, it is necessary to find out on a small scale, the ratio of the solutions of the two reactants required for complete neutralisation before preparation.

(b) Iron (III) Chloride (FeCl₃) is highly deliquescent. So, to keep it dry fused calcium chloride is used which is a drying agent.

(c) Anhydrous FeCl₃ cannot be prepared by heating the hydrated Iron (III) chloride (FeCl₃.6H₂O) because on heating, FeCl₃.6H₂O produces Fe₂O₃, H₂O, HCl.

2[FeCl₃.6H₂O] $\xrightarrow{\space\Delta\space}$ Fe₂O₃ + 9H₂O + 6HCl

Question 10

Match the salts given in column A to their methods of preparation in column B. Write a balanced equation for each preparation.

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

Exercise 3B

Answer:

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

Question 11(a)

Give the pH value of pure water. Does it change if common salt is added to it.

Exercise 3B

Answer:

pH of pure water is 7. No, it does not change when common salt is added.

Common salt is sodium chloride (NaCl). It is a salt derived from a strong acid (HCl) and strong base (NaOH) hence it gives a neutral solution with water.

Question 11(b)

Classify the following solutions as acids, bases or salts.

Ammonium hydroxide, barium chloride, sodium chloride, sodium hydroxide, H₂SO₄ and HNO₃

Exercise 3B

Answer:

Acids — H₂SO₄ and HNO₃

Bases — Ammonium hydroxide and sodium hydroxide.

Salts — Barium chloride and sodium chloride.

Question 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) + Soluble salt solution (B)	Precipitated salt + soluble salt	...............
Carbonate/bicarbonate + Acid (dil)	Salt + ............... + ...............	Decomposition of carbonate
Chlorides/nitrates + Acid (conc.)	............... + ...............	Decomposition of chlorides and nitrates.

Exercise 3B

Answer:

Completed table along with the equations is given below:

Sl. No.	Reactants	Products	Method
1.	Soluble base + Acid (dil)	Salt + water	Neutralisation Titration
1.	Eqn: HNO₃ + NaOH &amplongrightarrow NaNO₃ + H₂O
2.	Metal + Non-metal	Salt (soluble/insoluble)	*Direct combination*
2.	Eqn: 2Fe + 3Cl₂ &amplongrightarrow 2FeCl₃
3.	Insoluble base + *acid*	Salt (soluble) + water	*Neutralisation*
3.	Eqn: 2HCl + MgO &amplongrightarrow MgCl₂ + H₂O
4.	Active metal + Acid (dil)	*salt* + *hydrogen*	*Simple Displacement*
4.	Eqn: Fe + 2HCl &amplongrightarrow FeCl₂ + H₂ ↑
5.	Soluble salt solution (A) + Soluble salt solution (B)	Precipitated salt + soluble salt	*Precipitation*
5.	Eqn: Na₂SO₄ + BaCl₂ &amplongrightarrow BaSO₄ ↓ + 2NaCl
6.	Carbonate/bicarbonate + Acid (dil)	Salt + *water* + *carbon dioxide*	Decomposition of carbonate
6.	Eqn: MgCO₃ + H₂SO₄ &amplongrightarrow MgSO₄ + H₂O + CO₂ ↑
7.	Chloride/nitrate + Acid (conc.)	*salt* + *acid (HCl/HNO₃)*	Decomposition of chloride and nitrates.
7.	Eqn: AgNO₃ + HCl &amplongrightarrow AgCl ↓ + HNO₃

Question 13

Write the balanced equations 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,

(d) A soluble sulphate by the action of an acid on a metal.

Exercise 3B

Answer:

(a) CuO + H₂SO₄ ⟶ CuSO₄ + H₂O

(b) AgNO₃ + HCl ⟶ AgCl ↓ + HNO₃

(d) Zn + H₂SO₄ ⟶ ZnSO₄ + H₂↑

Question 14

You are provided with the following chemicals:

NaOH, Na₂CO₃, H₂O, Zn(OH)₂, CO₂, HCl, Fe, H₂SO₄, Cl₂, Zn.

Using the suitable chemicals from the given list only, state briefly how you would prepare :

(a) iron (III) chloride

(b) sodium sulphate

(d) iron (II) sulphate

(e) sodium chloride

Exercise 3B

Answer:

(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

(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

Question 15

For each of the salt : A, B, C and D, suggest a suitable method of it's preparation.

(a) A is a sodium salt,

(b) B is an insoluble salt,

(d) D is a soluble salt of zinc.

Exercise 3B

Answer:

(a) By neutralisation:
NaOH + HCl ⟶ NaCl + H₂O

(b) By precipitation:
AgNO₃ + HCl ⟶ AgCl + HNO₃

(d) Simple displacement:
Zn + H₂SO₄ ⟶ ZnSO₄ + H₂↑

Question 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

(d) Zinc carbonate

Dilute sulphuric acid	Copper	Copper carbonate
	Iron	Sodium carbonate
	Sodium
	Zinc

Exercise 3B

Answer:

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

Question 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.

(d) on heating, this salt changes from green to black.

(e) this salt gives nitrogen dioxide on heating.

Exercise 3B

Answer:

(a) NaHSO₄

(b) AgCl

(d) CuCO₃

(e) Pb(NO₃)₂

Question 18

(a) Ca(H₂PO₄)₂ is an example of compound called ............... (acid salt / basic salt / normal salt).

(b) Write the balanced equation for the reaction of :
A named acid and a named alkali.

Exercise 3B

Answer:

(a) Ca(H₂PO₄)₂ is an example of compound called acid salt

(b) NaOH + HCl ⟶ NaCl + H₂O

Question 19

State the terms defined by the following sentences:

(a) A soluble base

(b) The insoluble solid formed when two solution are mixed together.

Exercise 3B

Answer:

(a) Alkali

(b) Precipitate

Question 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	Neutralization 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

Exercise 3B

Answer:

The methods for preparation of the given chlorides are listed below:

Sl. No.	Chloride	Method
(i)	Copper (II) chloride	B
(ii)	Iron (II) chloride	A
(iii)	Iron (III) chloride	C
(iv)	Lead (II) chloride	E
(v)	Sodium chloride	D

Question 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.

(d) An amphoteric oxide

Exercise 3B

Answer:

(a) SiO₂

(b) SO₂

(d) Al₂O₃

Exercise 3C

11 questions

Question 1

What do you understand by the water of crystallisation?

Give four substances which contain water of crystallisation and write their common names.

Exercise 3C

Answer:

It is the amount of water molecules which enter into loose chemical combination with the salts and can be driven out by heating the crystals above 100°C.

Chemical name	Formula	Common name
Sodium carbonate decahydrate	Na₂CO₃.10H₂O	Washing soda crystals
Magnesium sulphate heptahydrate	MgSO₄.7H₂O	Epsom salt
Sodium sulphate decahydrate	Na₂SO₄.10H₂O	Glauber's salt
Copper (II) sulphate pentahydrate	CuSO₄.5H₂O	Blue vitriol

Question 2

(a) Define efflorescence. Give examples.

(b) Define deliquescence. Give examples.

Exercise 3C

Answer:

(a) Efflorescence is the property of some salts to loose wholly or partly their water of crystallisation when their crytals are exposed to dry air even for a short time.

Examples: MgSO₄.7H₂O (Epsom salt) , Na₂SO₄.10H₂O (Glauber's salt).

(b) Certain water-soluble substances, when exposed to the atmosphere at ordinary temperature, absorb moisture from the atmospheric air to become moist and ultimately dissolve in the absorbed water, forming a saturated solution. The phenomenon is called deliquescence and the salts are called deliquescent.

Examples: Caustic soda (NaoH), Caustic potash (KOH)

Question 3

Answer the questions below:

(a) What name is given to the water in the compound copper sulphate-5-water?

(b) If copper sulphate-5-water is heated, anhydrous copper sulphate is formed. What is it's colour?

(d) Name a deliquescent salt.

(e) Why does hydrated copper sulphate turn white on heating?

Exercise 3C

Answer:

(a) Water of crystallization

(b) White

(d) Iron [III] chloride FeCl₃

(e) The blue coloured hydrous copper sulphate changes to white anhydrous copper sulphate as the water of crystallization is removed on heating.
CuSO₄.5H₂O ⟶ CuSO₄ + 5H₂O

Question 4

State your observation when the following are exposed to the atmosphere:

(a) Washing soda crystals

(b) Iron (III) chloride salts.

Exercise 3C

Answer:

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

Na₂CO₃.10H₂O $\xrightarrow{\space\text{dry air}\space}$ Na₂CO₃.H₂O + 9H₂O

(b) When Iron (III) chloride (FeCl₃) is exposed to the atmosphere at ordinary temperature, it absorbs moisture from the atmospheric air to become moist and ultimately dissolve in the absorbed water, forming a saturated solution.

Question 5

Give reasons for the following:

(a) Sodium hydrogen sulphate is not an acid, but it dissolves in water to give hydrogen ions according to the equation

NaHSO₄ ⇌ H⁺ + Na⁺ + SO₄^2-

(b) Anhydrous calcium chloride is used in a desiccator.

Exercise 3C

Answer:

(a) Sodium hydrogen sulphate [NaHSO₄] is not an acid but due to the partial replacement of the replaceable hydrogen ion in a dibasic acid [H₂SO₄] releases a [H⁺] ion. Thus, we get the above equation.

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

(b) Desiccating agents are used to absorb moisture. Anhydrous calcium chloride (CaCl₂) has the capacity to absorb moisture as it is hygroscopic hence used as a desiccating agent.

Question 6

Explain clearly how conc. H₂SO₄ is used as a dehydrating as well as a drying agent.

Exercise 3C

Answer:

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

Conc. sulphuric acid can remove water molecules from blue vitriol (CuSO₄.5H₂O), so it is a dehydrating agent as well.

Question 7

Distinguish between drying and dehydrating agent.

Exercise 3C

Answer:

Drying Agent	Dehydrating Agent
Drying Agents remove moisture from other substances.	Dehydrating Agents remove chemically combined elements of water in the ratio of 2:1 (hydrogen:oxygen) from a compound.
Drying Agents are used to dry gases like chlorine, sulphur dioxide and hydrogen chloride. They are also used in dessicators to keep substances dry.	Dehydrating Agents prepare substances such as carbon monoxide and sugar charcoal.
They represent a physical change.	They represent a chemical change.
Example: Phosphorous pentoxide (P₂O₅), Calcium Oxide (CaO)	Example: Conc. Sulphuric Acid H₂SO₄

Question 8

State whether a sample of each of the following would increase or decrease in mass if exposed to air.

(a) Solid NaOH

(b) Solid CaCl₂

(d) Conc. Sulphuric acid

(e) Iron (III) Chloride

Exercise 3C

Answer:

(a) Increase

(b) Increase

(d) Increase

(e) Increase

Explanation — Efflorescent substances lose their weight while hygroscopic and deliquescent substances gain weight when exposed to atmosphere. Solid NaOH, Solid CaCl₂ and Iron (III) Chloride (FeCl₃) are deliquescent substances while Conc. Sulphuric acid is hygroscopic hence they gain weight when exposed to air. Solid Na₂CO₃.10H₂O is an efflorescent substance hence it loses weight.

Question 9

(a) Why does common salt get wet during the rainy season?

(b) How can this impurity be removed?

(d) Name two crystalline substances which do not contain water of crystallisation.

Exercise 3C

Answer:

(a) Common salt gets wet during the rainy season, as it is deliquescent and absorbs moisture from the atmosphere. Though pure sodium chloride is not deliquescent, the commercial version of the salt contains impurities like, magnesium chloride and calcium 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.

(d) Common salt and sugar

Question 10

Name the salt which on hydrolysis forms

(a) Acidic

(b) Basic and

Give a balanced equation for each reaction.

Exercise 3C

Answer:

(a) Iron chloride(FeCl₃)

FeCl₃ + 3H₂O ⟶ 3HCl + Fe(OH)₃

(b) Ammonium acetate (CH₃COONH₄)

CH₃COONH₄ + H₂O ⟶ CH₃COOH + NH₄OH

NaCl + H₂O ⟶ NaOH + HCl

Question 11

State the change noticed when blue litmus and red litmus are introduced in the following solutions:

(a) Na₂CO₃ solution

(b) NaCl solution

(d) MgCl₂ Solution

Exercise 3C

Answer:

(a) Na₂CO₃ solution — Red litmus changes to blue as Na₂CO₃ gives alkaline solution.

(b) NaCl solution — No change in the colour of the litmus paper as NaCl solution is neutral.

(d) MgCl₂ solution — Blue litmus changes to red showing acidic nature.

Intext Questions 1

14 questions

Question 1

(a) What to you understand by the term acid?

(b) Name the positive ion formed when an acid is dissolved in water.

Intext Questions 1

Answer:

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

(b) Hydronium ion (H₃O⁺)

Draw the structure of the stable positive ion formed when an acid dissolves in water. Acids, Bases and Salts, Concise Chemistry Solutions ICSE Class 10

Question 2

Write the ionisation of sulphuric acid showing the formation of hydronium ion.

Intext Questions 1

Answer:

H₂SO₄ + H₂O ⇌ H₃O⁺ + HSO₄^-

HSO₄^- + H₂O ⇌ H₃O⁺ + SO₄^2-

Question 3

Water is never added to acid in order to dilute it. Why?

Intext Questions 1

Answer:

Water is not added to acid as it is an exothermic process and in this process so much heat is produced that splashing of acidic acid solution may occur, also the container may break which can be fatal to the person.

Question 4

Define the term 'basicity' of an acid. Give the basicity of: nitric acid, sulphuric acid and phosphoric acid.

Intext Questions 1

Answer:

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:

Basicity of Nitric acid = 1

Basicity of Sulphuric acid = 2

Basicity of Phosphoric acid = 3

Question 5

Give two examples of each of the following :

(a) oxy-acid

(b) hydracid

(d) dibasic acid

Intext Questions 1

Answer:

(a) Oxyacids — Nitric acid [HNO₃] and Sulphuric acid [H₂SO₄]

(b) Hydracid — Hydrochloric acid [HCl] and Hydrobromic acid [HBr]

(d) Dibasic acid — Sulphuric acid [H₂SO₄] and Carbonic acid [H₂CO₃]

Question 6

Name the :

(a) acidic anhydride of the following acids:

sulphurous acid
nitric acid
phosphoric acid
carbonic acid

(b) acid present in vinegar, grapes and lemons.

Intext Questions 1

Answer:

(a) Below are the acidic anhydride of the given acids:

Sulphurous acid — SO₂
Nitric acid — N₂O₅
Phosphoric acid — P₂O₅
Carbonic acid — CO₂

(b) Acids present in following are:

Vinegar — Acetic acid
Grapes — Tartaric acid
Lemon — Citric acid

Question 7

What do you understand by the statement 'acetic acid is a monobasic acid'?

Intext Questions 1

Answer:

Acetic acid is a monobasic acid because it's molecule ionises by liberating only one hydronium ion.

CH₃COOH + H₂O ⇌ H₃O⁺ + CH₃COO^-

Question 8

Give a balanced equation for :

(i) reaction of nitrogen dioxide with water

(ii) preparation of a non volatile acid from a volatile acid.

Intext Questions 1

Answer:

(i) 2NO₂ + H₂O ⟶ HNO₂ + HNO₃

(ii) S + 6HNO₃ ⟶ H₂SO₄ + 2H₂O + 6NO₂

Question 9

What do you understand by the strength of an acid? On which factor does the strength of an acid depend.

Intext Questions 1

Answer:

The strength of an acid is the measure of concentration of hydronium ions [H₃O⁺] produced by that acid in aqueous solution.

Factors on which the strength of an acid depends are:

Degree of ionisation (α).
Concentration of hydronium ions [H₃O⁺] produced by that acid in aqueous solution.

Question 10

Explain the following:

(a) Carbonic acid gives an acid salt but hydrochloric acid does not.

(b) Dil. HCl acid is stronger than highly concentrated acetic acid.

(d) Lead carbonate does not react with dil. HCl

(e) Nitrogen dioxide is a double acid anhydride.

Intext Questions 1

Answer:

(a) Carbonic acid is a dibasic acid i.e., it has two replaceable hydrogen ions. Hence, it forms one acid salt or one normal salt. On the other hand, hydrochloric acid is a monobasic acid with one replaceable hydrogen ion. Hence, it forms only one normal salt.

(b) Concentration of an acid means the amount of water present in the acid and not at all the strength of an acid. Strength of an acid is the measure of concentration of hydronium ions it produces in its aqueous solution. Thus, dil. HCl is stronger acid than highly concentrated acetic acid.

(c) H₃PO₃ is not a tribasic acid but dibasic 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.

Explain why H3PO3 is not a tribasic acid. Acids, Bases and Salts, Concise Chemistry Solutions ICSE Class 10

(d) Generally, acids liberate carbon dioxide on reaction with metallic carbonates and bicarbonates. But if the salt produced is insoluble, then the reaction does not proceed. So, we do not expect lead carbonate to react with hydrochloric acid.

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

2NO₂ + H₂O ⟶ HNO₂ + HNO₃

Question 11

How is an acid prepared from a (a) Non-metal (b) salt ? Give an equation for each.

Intext Questions 1

Answer:

(a) A non-metal, e.g., sulphur or phosphorous is oxidised by conc. nitric acid to form to form sulphuric acid or phosphoric acid respectively.

S + 6HNO₃ ⟶ H₂SO₄ + 2H₂O + 6NO₂

P + 5HNO₃ ⟶ H₃PO₄ + H₂O + 5NO₂

(b) Normal salts of more volatile acids are displaced by a less or non-volatile acid.

E.g., Both hydrochloric acid and nitric acid are formed by using sulphuric acid [H₂SO₄].

NaCl + H₂SO₄ $\xrightarrow{\space\Delta\space}$ NaHSO₄ + HCl

NaNO₃ + H₂SO₄ $\xrightarrow{\space\Delta\space}$ NaHSO₄ + HNO₃

Question 12

Give equations to show how the following are made from their corresponding anhydrides.

(a) sulphurous acid

(b) phosphoric acid

(d) sulphuric acid

Intext Questions 1

Answer:

(a) SO₂ + H₂O ⟶ H₂SO₃

(b) P₂O₅ + 3H₂O ⟶ 2H₃PO₄

(d) SO₃ + H₂O ⟶ H₂SO₄

Question 13

Name an acid used:

(a) to flavour and preserve food;

(b) in a drink

(d) as an eyewash.

Intext Questions 1

Answer:

(a) Citric acid

(b) Carbonic acid

(d) Boric acid

Question 14

Give reaction of acids with

(a) chlorides

(b) nitrates

State the conditions under which they react.

Intext Questions 1

Answer:

(a) Chlorides do not react with dilute acids. They react with concentrated sulphuric acid on warming to liberate hydrogen chloride.

$\text{NaCl} + \text{H}_2\text{SO}_4 [\text{conc.}] \xrightarrow{\lt 200 \degree\text{C}}\text{NaHSO}_4 + \text{HCl}$

$2\text{NaCl} + \text{H}_2\text{SO}_4 [\text{conc.}] \xrightarrow{\gt 200 \degree\text{C}}\text{Na}_2\text{SO}_4 + 2\text{HCl}$

(b) Nitrates do not react with dilute acids. When heated with conc. sulphuric acid they produce more volatile nitric acid.

$\text{KNO}_3 + \text{H}_2\text{SO}_4 [\text{conc.}] \xrightarrow{\lt 200 \degree\text{C}}\text{KHSO}_4 + \text{HNO}_3$

$2\text{KNO}_3 + \text{H}_2\text{SO}_4 [\text{conc.}] \xrightarrow{\gt 200 \degree\text{C}}\text{K}_2\text{SO}_4 + 2\text{HNO}_3$

Miscellaneous Exercises Long Answer Type

5 questions

Question 1

Draw the structure of the stable positive ion formed when an acid dissolves in water.

Miscellaneous Exercises Long Answer Type

Answer:

Hydronium ion is the stable positive ion formed when an acid dissolves in water. Its structure is shown below:

Draw the structure of the stable positive ion formed when an acid dissolves in water. Acids, Bases and Salts, Simplified Chemistry Dalal Solutions ICSE Class 10

Question 2

Write balanced reactions for the following conversions (A,B,C,D)

$\text{Fe} \xrightarrow{\text{A}} \text{FeCl}_2 \xrightarrow{\text{B}} \text{FeCO}_3 \xrightarrow{\text{C}} \text{Fe}(\text{NO}_3)_2 \xrightarrow{\text{D}} \text{Fe(OH)}_2$

Miscellaneous Exercises Long Answer Type

Answer:

A = HCl

B = Na₂CO₃

C = HNO₃

D = NaOH

A: Fe + 2HCl ⟶ FeCl₂ + H₂ ↑

B: FeCl₂ + Na₂CO₃ ⟶ FeCO₃ + 2NaCl

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

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

Question 3

Give an equation for the conversions A to E —

Miscellaneous Exercises Long Answer Type

Answer:

(i) ZnSO₄ + Na₂CO₃ ⟶ Na₂SO₄ + ZnCO₃ ↓

(ii) ZnCO₃ + 2HNO₃ ⟶ Zn(NO₃)₂ + H₂O + CO₂ ↑

(iii) Zn(NO₃)₂ + 2NaOH ⟶ Zn(OH)₂ + 2NaNO₃

(iv) Zn(OH)₂ $\xrightarrow{\space\Delta\space}$ ZnO + H₂O

(v) ZnO + H₂SO₄ ⟶ ZnSO₄ + H₂O

Question 4

The preparation of lead sulphate from lead carbonate is a two step process. (lead sulphate cannot be prepared by adding dilute sulphuric acid to lead carbonate.)

(a) What is the first step that is required to prepare lead sulphate from lead carbonate?

(b) Write the equation for the reaction that will take place when this first step is carried out.

(c) Why is the direct addition of dilute sulphuric acid to lead carbonate an impractical method of preparing lead sulphate?

Miscellaneous Exercises Long Answer Type

Answer:

(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) Adding dilute sulphuric acid (H₂SO₄) to lead carbonate (PbCO₃) in order to prepare lead sulphate (PbSO₄) is an impractical method because an insoluble crust of lead sulphate is formed on lead carbonate which prevents further reaction.

Question 5

The diagram given below is to prepare Iron [III] chloride in the laboratory.

(i) What is substance B?

(ii) What is the purpose of B?

(iii) Why is iron[III] chloride to be stored in a closed container?

(iv) Write the equation for the reaction between iron and chlorine.

Miscellaneous Exercises Long Answer Type

Answer:

(i) Substance B is fused calcium chloride.

(ii) Iron (III) chloride is highly deliquescent so it is kept dry with the help of B [fused calcium chloride (drying agent)]

(iii) Iron[III] chloride is to be stored in a closed container because iron (III) chloride is highly deliquescent and it absorbs moisture from the surrounding air to form a saturated solution.

(iv) 2Fe (heated) + 3Cl₂ (dry) ⟶ 2FeCl₃

Miscellaneous Exercises Multiple Choice Type

13 questions

Question 1

The acid which contains four hydrogen atoms is :

Formic acid
Sulphuric acid
Nitric acid
Acetic acid

Miscellaneous Exercises Multiple Choice Type

Answer:

Acetic acid

Reason — The formulas of the given acids are:

Acid	Formula
Formic acid	HCOOH
Sulphuric acid	H₂SO₄
Nitric acid	HNO₃
Acetic acid	CH₃COOH

Hence, out of the given acids, Acetic acid contains four hydrogen atoms.

Question 2

A black coloured solid which on reaction with dilute sulphuric acid forms a blue coloured solution is :

Carbon
Manganese [IV] oxide
Lead [II] oxide
Copper [II] oxide

Miscellaneous Exercises Multiple Choice Type

Answer:

Copper [II] oxide

Reason — Copper [II] oxide is black in colour and the following reaction takes place when it is treated with dilute sulphuric acid —

CuO + H₂SO₄ ⟶ CuSO₄ + H₂O

CuSO₄ is a blue coloured soln.

Question 3

A weak organic acid is :

Formic acid
Sulphuric acid
Nitric acid
Hydrochloric acid

Miscellaneous Exercises Multiple Choice Type

Answer:

Formic acid

Reason — Formic acid (HCOOH) is a weak organic acid whereas Sulphuric acid (H₂SO₄), Nitric acid (HNO₃) and Hydrochloric acid (HCl) are strong mineral (or inorganic) acids.

Question 4

A complex salt is :

Zinc sulphate
Sodium hydrogen sulphate
Iron [ammonium sulphate]
Tetraammine copper [II] sulphate

Miscellaneous Exercises Multiple Choice Type

Answer:

Tetraammine copper [II] sulphate

Reason — Tetraammine copper [II] sulphate ([Cu(NH₃)₄]SO₄) is a complex salt as on dissociation, it gives one simple ion and one complex ion:

[Cu(NH₃)₄]SO₄ ⟶ [Cu(NH₃)₄]²⁺ + SO₄^2-

Question 5

Which one of the following will not produce acid with water ?

CO
CO₂
NO₂
SO₃

Miscellaneous Exercises Multiple Choice Type

Answer:

Reason — Carbon monoxide reacts with water to form carbon dioxide and releases hydrogen gas. Hence, acid is not formed.

CO + H₂O ⟶ CO₂ + H₂

Question 6

The basicity of acetic acid is:

Miscellaneous Exercises Multiple Choice Type

Answer:

Reason — Acetic acid has four hydrogen atoms in it but it ionises in aqueous solution to produce one hydrogen ion per molecule of the acid. Hence, basicity of acetic acid is 1.

Question 7

Lead sulphate can be prepared by the following methods.

P Reacting lead with sulphuric acid.
Q Reacting lead nitrate with sodium sulphate solution.
R Reacting lead oxide with sodium sulphate solution.

(a) Only P
(b) Only Q
(c) Only R
(d) Both Q and R

Miscellaneous Exercises Multiple Choice Type

Answer:

Only Q

Reason — Insoluble lead sulphate is prepared from insoluble lead carbonate or insoluble lead oxide by first converting them into soluble lead nitrate (with the help of dilute nitric acid).

PbCO₃ + 2HNO₃ → Pb(NO₃)₂ + CO₂ + H₂O
PbO + 2HNO₃ → Pb(NO₃)₂ + H₂O

The resulting solution is then treated with sodium sulphate solution to get lead sulphate as a white precipitate.

Pb(NO₃)₂ + Na₂SO₄ → PbSO₄ ↓ + 2NaNO₃

Question 8

Assertion (A): All acids form hydronium ions when dissolved in water.

Reason (R): Every acid has hydrogen as the necessary element.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not the correct explanation of A

(d) A is false but R is true

Miscellaneous Exercises Multiple Choice Type

Answer:

Both A and R are true and R is the correct explanation of A.

Explanation — When dissolved in water, acids donate protons (H⁺), which associate with water molecules to form hydronium ions (H₃O⁺).
Acids are defined as compounds which contain one or more hydrogen atoms and when dissolved in water, produce hydronium ions (H₃O⁺) as the only positively charged ions. Hence both assertion (A) and reason (B) are true and (R) correctly explains (A).

Question 9

Assertion (A): All bases react with acids to form salt and water only.

Reason (R): All alkalis are bases but all bases are not alkalis.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.

Miscellaneous Exercises Multiple Choice Type

Answer:

Both A and R are true but R is not the correct explanation of A.

Explanation — All bases react with acid to form salt and water. This reaction is called as neutralisation reaction. Hence the assertion (A) is true.

Alkalis are bases that are soluble in water. All alkalis are bases but all bases are not alkalis.
For example: Ferric hydroxide [Fe (OH) ₃ ] and Cupric hydroxide [Cu (OH) ₂] are bases, but not alkalis because they are insoluble in water. Hence reason (R) is also true but it does not support the assertion (A).

Question 10

Assertion (A): Acids which contain carbon are necessarily organic acids.

Reason (R): All organic acids are derived from plants and animals.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.

Miscellaneous Exercises Multiple Choice Type

Answer:

A is false but R is true.

Explanation — Every acid that contains carbon is not an organic acid.
Example: Carbonic acid (H₂CO₃) contains carbon but is an inorganic acid. Hence the assertion (A) is false. Acids that are derived from plants and animals are all organic acids. Hence the reason (R) is true.

Question 11

Assertion (A): Acids have a pH of more than 7.

Reason (R): Acids produce hydronium ions as the only positively charged ion in solution.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.

Miscellaneous Exercises Multiple Choice Type

Answer:

A is false but R is true.

Explanation — The pH of an acid is less than 7. Hence the assertion (A) is false. Reason (R) is true because, acids are defined as compounds which contain one or more hydrogen atoms and when dissolved in water, produces hydronium ion as the only positively charged ions.

Question 12

Assertion (A): Iron (III) chloride is stored in a moisture proof container.

Reason (R): Iron (III) chloride is hygroscopic in nature.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.

Miscellaneous Exercises Multiple Choice Type

Answer:

A is true but R is false.

Explanation — Iron (III) chloride is highly deliquescent that means it is a substance, that absorbs moisture from the air and dissolves, becoming a liquid. So it is kept dry in a moisture proof container with the help of fused calcium chloride (drying agent). Hence given assertion (A) is true.

Reason (R) is false because iron (III) chloride being deliquescent, dissolves in water to form liquid solution whereas hygroscopic substances absorb moisture from the air, but do not dissolve in it.

Question 13

Assertion (A): Water is added to acids to dilute them.

Reason (R): The addition of water to acids is a highly exothermic reaction. Splashes of acid solution may come in contact with skin and container may also break.

Both A and R are true and R is the correct explanation of A.
Both A and R are true but R is not the correct explanation of A.
A is true but R is false.
A is false but R is true.

Miscellaneous Exercises Multiple Choice Type

Answer:

A is false but R is true.

Explanation — Acids are diluted by adding acid to water, not by adding water to acid. The goal is to reduce the concentration of hydrogen ions (H⁺) in solution safely. Hence the assertion (A) is false.

Reason (R) is true because water is not added to acid as it is an exothermic process and in this process so much heat is produced that splashing of acidic solution may occur, also the container may break which can be fatal to the person.

Miscellaneous Exercises Short Answer Type

9 questions

Question 1

Define Neutralization.

Miscellaneous Exercises Short Answer Type

Answer:

Neutralization — It is the process due to which [H⁺] ions of an acid react completely or combine with [OH^-] ions of a base to give salt and water only.

Acid + Base ⟶ Salt + Water

HCl + NaOH ⟶ NaCl + H₂O

H⁺Cl^- + Na⁺OH^- ⟶ Na⁺Cl^- + H₂O

[H⁺ (aq) + OH^- (aq) ⇌ H₂O (l)]

Question 2

State your observation when zinc granule is added to copper sulphate solution.

Miscellaneous Exercises Short Answer Type

Answer:

Zinc displaces copper to form zinc sulphate and thus copper gets deposited and the blue coloured solution becomes colourless.

Zn + CuSO₄ ⟶ Cu + ZnSO₄

Question 3

Salt S is prepared by reacting dilute sulphuric acid with copper oxide. Identify S.

Miscellaneous Exercises Short Answer Type

Answer:

Salt S is Copper sulphate CuSO₄

CuO + H₂SO₄ (dil.) ⟶ CuSO₄ + H₂O

Question 4

From the substances given in the list below, write the equations for the reactions by which you could obtain the compounds given ahead :

Dilute sulphuric acid	sodium carbonate
Zinc	sodium sulphite
Lead	calcium carbonate

hydrogen,
sulphur dioxide,
carbon dioxide,
zinc carbonate (two steps required).

Miscellaneous Exercises Short Answer Type

Answer:

Equations for the reactions are :

Zn + H₂SO₄ ⟶ ZnSO₄ + H₂↑
Na₂SO₃ + 2HCl ⟶ 2NaCl + H₂O + SO₂↑
Na₂CO₃ + H₂SO₄ $\xrightarrow{\space\Delta\space}$ Na₂SO₄ + H₂O + CO₂↑
Zn + H₂SO₄ ⟶ ZnSO₄ + H₂↑
ZnSO₄ + Na₂CO₃ ⟶ Na₂SO₄ + ZnCO₃

Question 5

Choosing the substances from the list given:

dil. Sulphuric acid, Copper, Iron, Sodium, Copper (II) carbonate, Sodium carbonate, Sodium chloride, Zinc nitrate

Write balanced equations for the reactions which would be used in the laboratory to obtain the following salts:

Sodium sulphate
Zinc carbonate
Copper (II) sulphate
Iron (II) sulphate.

Miscellaneous Exercises Short Answer Type

Answer:

Sodium sulphate
Na₂CO₃ + H₂SO₄ (dil.) ⟶ Na₂SO₄ + H₂O + CO₂
Zinc carbonate
Zn(NO₃)₂ + Na₂CO₃⟶ 2NaNO₃ + ZnCO₃
Copper (II) sulphate
CuCO₃ + H₂SO₄ (dil.) ⟶ CuSO₄ + H₂O + CO₂
Iron (II) sulphate
Fe + H₂SO₄ (dil.) ⟶ FeSO₄ + H₂

Question 6

You are given three solutions A, B and C. A is a strong acid, B is a weak acid and C is a strong alkali.

(a) Which solution contains solute molecules in addition to water molecules ?

(b) Which solution gives gelatinous white precipitate with zinc sulphate which disappears in excess solution ?

Miscellaneous Exercises Short Answer Type

Answer:

(a) Solution B — weak acid
Reason — Weak Acid is an acid which dissociates only partially in aqueous solution thereby producing a low concentration of hydrogen [H⁺] ions [or H₃O⁺ ions]. For example — CH₃COOH ⇌ CH₃COO^- + H⁺ [contains molecules and ions]

(b) Solution C — strong alkali
Reason — Alkalis react with certain salt solutions to precipitate insoluble hydroxide. Hence,
ZnSO₄ + 2NaOH ⟶ Na₂SO₄ + Zn(OH)₂ [gelatinous white precipitate]

Question 7

Write balanced chemical equations for the following:

(a) Reaction of silver nitrate solution and sodium chloride solution.

(b) Lead nitrate solution is added to sodium chloride solution.

Miscellaneous Exercises Short Answer Type

Answer:

(a) AgNO₃ + NaCl ⟶ NaNO₃ + AgCl ↓

(b) Pb(NO₃)₂ + 2NaCl ⟶ PbCl₂ ↓ + 2NaNO₃

(c) When crystals of washing soda are exposed to air, it loses its water of crystallisation and the phenomenon is known as Efflorescence.

Question 8

Give a balanced equation for the preparation of the following salts:

(a) Copper [II] sulphate from copper [II] oxide.

(b) Iron [III] chloride from the metal iron.

(d) Potassium sulphate from KOH solution.

(e) Lead [II] chloride from lead carbonate [give two equations].

(f) Sodium sulphate — using dilute sulphuric acid.

(g) Copper chloride — using copper carbonate.

Miscellaneous Exercises Short Answer Type

Answer:

(a) CuO + H₂SO₄ ⟶ CuSO₄ + H₂O

(b) 2Fe + 3Cl₂ ⟶ 2FeCl₃

(d) 2KOH + H₂SO₄ [dil.] ⟶ K₂SO₄ + 2H₂O

(e) PbCO₃ + 2HNO₃ ⟶ Pb(NO₃)₂ + H₂O + CO₂ ↑
Pb(NO₃)₂ + 2NaCl ⟶ 2NaNO₃ + PbCl₂

(f) Na₂CO₃ + H₂SO₄(dil.) ⟶ Na₂SO₄ + H₂O + CO₂

(g) CuCO₃ + 2HCl (dil) ⟶ CuCl₂ + H₂O + CO₂

Question 9

Write the balanced equations for the preparation of the following compounds (as the major product) starting from iron and using only one other substance :

(a) Iron (II) chloride

(b) Iron (III) chloride

(d) Iron (II) sulphide

Miscellaneous Exercises Short Answer Type

Answer:

(a) Fe + 2HCl (dil) ⟶ FeCl₂ + H₂↑

(b) 2Fe (heated) + 3Cl₂ (dry) ⟶ 2FeCl₃

(d) Fe + S $\xrightarrow{\space\Delta\space}$ FeS

Miscellaneous Exercises Very Short Answer Type

10 questions

Question 1(a)

(a) A solution has a pH of 7. Explain how you would:

(i) increase its pH;

(ii) decrease its pH;

Miscellaneous Exercises Very Short Answer Type

Answer:

(i) By adding a base or alkali to the solution.

(ii) By add an acid to the solution.

Question 1(b)

If a solution changes the colour of litmus from red to blue what can you say about its pH?

Miscellaneous Exercises Very Short Answer Type

Answer:

Blue litmus indicates a basic solution, so the pH is greater than 7.

Question 1(c)

What can you say about the pH of a solution, that liberates carbon dioxide from sodium carbonate?

Miscellaneous Exercises Very Short Answer Type

Answer:

An acid will liberate carbon dioxide on reaction with sodium carbonate. So, the pH of the solution will be acidic, means below 7.

Question 2

Match the following:

Column A	Column B
(i) Acid salt	(A) Ferrous ammonium sulphate
(ii) Double salt	(B) Contains only ions
(iii) Ammonium hydroxide solution	(C) Sodium hydrogen sulphate
(iv) Dilute hydrochloric acid	(D) Contains only molecules
(v) Carbon tetrachloride	(E) Contains ions and molecules

Miscellaneous Exercises Very Short Answer Type

Answer:

Column A	Column B
(i) Acid salt	(C) Sodium hydrogen sulphate
(ii) Double salt	(A) Ferrous ammonium sulphate
(iii) Ammonium hydroxide solution	(E) Contains ions and molecules
(iv) Dilute hydrochloric acid	(B) Contains only ions
(v) Carbon tetrachloride	(D) Contains only molecules

Question 3

Match the salts given in column I with their method of preparation given in column II.

Column I	Column II
(i) Pb(NO₃)₂ from PbO	(A) Simple displacement
(ii) MgCl₂ from Mg	(B) Titration
(iii) FeCl₃ from Fe	(C) Neutralization
(iv) NaNO₃ from NaOH	(D) Precipitation
(v) ZnCO₃ from ZnSO₄	(E) Combination

Miscellaneous Exercises Very Short Answer Type

Answer:

Column I	Column II
(i) Pb(NO₃)₂ from PbO	(C) Neutralization
(ii) MgCl₂ from Mg	(A) Simple displacement
(iii) FeCl₃ from Fe	(E) Combination
(iv) NaNO₃ from NaOH	(B) Titration
(v) ZnCO₃ from ZnSO₄	(D) Precipitation

Question 4

From — Na₂O, SO₂, SiO₂, Al₂O₃, MgO, CO — Select an oxide which dissolves in water forming an acid.

Miscellaneous Exercises Very Short Answer Type

Answer:

SO₂

The following reaction takes place.

SO₂ + H₂O ⟶ H₂SO₃

Question 5

From the list given below, which one is :

a deliquescent compound
a compound soluble in hot water but insoluble in cold water
a compound which in the aqueous solution state, is neutral in nature.

A. Nitroso iron [II] sulphate
B. Iron [III] chloride
C. Chromium sulphate
D. Lead chloride
E. Sodium chloride

Miscellaneous Exercises Very Short Answer Type

Answer:

B: Iron [III] chloride
D: Lead [II] chloride
E: Sodium chloride

Question 6

From the list of salts — AgCl, MgCl₂, NaHSO₄, PbCO₃, ZnCO₃, KNO₃, Ca(NO₃)₂.

Choose the salt that most appropriately fits the description given below :

(i) a deliquescent salt

(ii) an insoluble chloride.

Miscellaneous Exercises Very Short Answer Type

Answer:

(i) MgCl₂

(ii) AgCl

Question 7

Give a suitable word or phrase for :

A salt formed by incomplete neutralisation of an acid by a base.
The definite number of water molecules bound to some salts.
The process in which a substance absorbs moisture from the atmospheric air to become moist, and ultimately dissolves in the absorbed water.
A salt containing a metal ion surrounded by other ions or molecules.
A base which is soluble in water.

Miscellaneous Exercises Very Short Answer Type

Answer:

Acid salt
Water of crystallisation
Deliquescence
Complex salts
Alkali

Question 8

Name the method used for the preparation of the following salts from the list given below –

(i) Sodium nitrate

(ii) Iron (III) chloride

(iii) Lead chloride

(iv) Zinc sulphate

(v) Sodium hydrogen sulphate.

List:

A : Simple displacement
B : Neutralization
C : Decomposition by acid
D : Double decomposition
E : Direct synthesis

Miscellaneous Exercises Very Short Answer Type

Answer:

(i) Sodium nitrate — B : Neutralization

(ii) Iron (III) chloride — E : Direct synthesis

(iii) Lead chloride — D : Double decomposition

(iv) Zinc sulphate — A : Simple displacement

(v) Sodium hydrogen sulphate — C : Decomposition by acid