Chapter 3A Acids, Bases and Salts Class 10 - Dalal Simplified ICSE Chemistry Solutions -

Chapter 3A Acids, Bases and Salts Class 10 – Dalal Simplified ICSE Chemistry Solutions

Equation Worksheet

Question 1

ACIDS — Ions present in acids	Complete and balance the equations
a. Definition — Dissolves in water yielding hydronium ions
1. Hydrochloric acid	HCl ⇌ …………… + Cl^– [H⁺ + H₂O ⇌ …………… ] HCl + H₂O ⇌ …………… + ……………
2. Nitric acid	HNO₃ + H₂O ⇌ …………… + ……………
3. Sulphuric acid	H₂SO₄ + H₂O ⇌ …………… + ……………
b. Classification
4. Monobasic acid [Basicity = 1 ]	HCl [aq.] ⇌ …………… + ……………
5. Dibasic acid [Basicity = 2]	H₂SO₄ [aq.] ⇌ …………… + ……………
6. Tribasic acid [Basicity = 3]	H₃PO₄ [aq.] ⇌ …………… + ……………
c. Preparation of acids
7. From non-metals	H₂ + Cl₂ ⟶ *……………*
8. From acidic oxides	CO₂ + H₂O ⟶ *……………*
	SO₃ + H₂O ⟶ ……………
	P₂O₅ + H₂O ⟶ ……………
9. From normal salts	KNO₃ + H₂SO₄ ⟶ …………… + ……………
	NaCl+ H₂SO₄ ⟶ …………… + ……………
10. By oxidation of non-metals	S + HNO₃ ⟶ …………… + H₂O …………… [g]
d. Properties of acids
11. Neutralizes bases	CuO + H₂SO₄ ⟶ …………… + ……………
	NaOH + HCl ⟶ …………… + ……………
Reaction with
12. Chlorides and nitrates	$NaCl + H_{2} SO_{4} [conc.] < 200° C \dots\dots\dots\dots\dots + \dots\dots\dots\dots\dots$
	$NaNO_{3} + H_{2} SO_{4} [conc.] < 200° C \dots\dots\dots\dots\dots + \dots\dots\dots\dots\dots$
13. Carbonates and bicarbonates	Na₂CO₃ + H₂SO₄ ⟶ …………… + H₂O + …………… [g]
	NaHCO₃ + H₂SO₄ ⟶ …………… + H₂O + …………… [g]
14. Sulphites and bisulphites	Na₂SO₃ + HCl ⟶ …………… + H₂O + …………… [g]
	NaHSO₃ + HCl ⟶ …………… + H₂O + …………… [g]
15. Active metals	Zn + HCl ⟶ …………… + …………… [g]

Answer

ACIDS — Ions present in acids	Complete and balance the equations
a. Definition — Dissolves in water yielding hydronium ions
1. Hydrochloric acid	HCl ⇌ H⁺ + Cl^– [H⁺ + H₂O ⇌ *H₃O⁺] HCl + H₂O ⇌ H₃O⁺* + *Cl^–*
2. Nitric acid	HNO₃ + H₂O ⇌ *H₃O⁺* + *NO₃^–*
3. Sulphuric acid	H₂SO₄ + 2H₂O ⇌ *2H₃O⁺* + *SO₄^2-*
b. Classification
4. Monobasic acid [Basicity = 1 ]	HCl [aq.] ⇌ *H₃O⁺* + *Cl^–*
5. Dibasic acid [Basicity = 2]	H₂SO₄ [aq.] ⇌ *2H₃O⁺* + *SO₄^2-*
6. Tribasic acid [Basicity = 3]	H₂PO₄ [aq.] ⇌ *3H₃O⁺* + *PO₄^3-*
c. Preparation of acids
7. From non-metals	H₂ + Cl₂ ⟶ *2HCl*
8. From acidic oxides	CO₂ + H₂O ⟶ *H₂CO₃*
	SO₃ + H₂O ⟶*H₂SO₄*
	P₂O₅ + 3H₂O ⟶*2H₃PO₄*
9. From normal salts	KNO₃ + H₂SO₄ ⟶*KHSO₄* + *HNO₃*
	NaCl+ H₂SO₄ ⟶*NaHSO₄* + *HCl*
10. By oxidation of non-metals	S + 6HNO₃ ⟶*H₂SO₄* + 2H₂O + *6NO₂* [g]
d. Properties of acids
11. Neutralizes base	CuO + H₂SO₄ ⟶ *CuSO₄* + *H₂O*
	NaOH + HCl ⟶ *NaCl* + *H₂O*
Reaction with
12. Chlorides and nitrates	$NaCl + H_{2} SO_{4} [conc.] < 200° C NaHSO_{4} + HCl$
	$NaNO_{3} + H_{2} SO_{4} [conc.] < 200° C NaHSO_{4} + HNO_{3}$
13. Carbonates and bicarbonates	Na₂CO₃ + H₂SO₄ ⟶ *Na₂SO₄* + H₂O + *CO₂ [g]*
	2NaHCO₃ + H₂SO₄ ⟶ *Na₂SO₄* + 2H₂O + *2CO₂ [g]*
14. Sulphites and bisulphites	Na₂SO₃ + 2HCl ⟶ *2NaCl* + H₂O + *SO₂ [g]*
	NaHSO₃ + HCl ⟶ *NaCl* + H₂O + *SO₂ [g]*
15. Active metals	Zn + 2HCl ⟶ *ZnCl₂* + H₂ [g]

Question 2

BASES — Ions present in bases
a. Alkali — dissociates yielding hydroxyl ions
16. Sodium hydroxide	NaOH [aq.] ⇌ …………… + ……………
17. Ammonium hydroxide	NH₄OH [aq.] ⇌ …………… + ……………
b. Classification
18. Monoacidic base [Acidity = 1 ]	KOH [aq.] ⇌ …………… + ……………
19. Diacidic base [Acidity = 2]	Cu(OH)₂ [aq.] ⇌ …………… + ……………
c. Preparation of bases
20. From metals	Na + O₂ ⟶ ……………
21. From metallic oxides and metals	K₂O + H₂O ⟶ ……………
	K + H₂O ⟶ …………… + ……………
22.From salts	AlCl₃ + NaOH ⟶ …………… + …………… ↓
	FeSO₄ + NaOH ⟶ …………… + …………… ↓
23. By thermal decomposition	ZnCO₃ ⟶ …………… + …………… [g]
	Pb(NO₃)₂ ⟶ …………… + ……………[g] + ………….. [g]
c. Properties of bases
24. Neutralizes acids	PbO + HNO₃ ⟶ …………… + ……………
	Fe(OH)₂ + HCl ⟶ …………… + ……………
Reaction with
25. Metallic salt solution	CuCl₂ + NaOH ⟶ …………… + …………… ↓
	FeCl₃ + NaOH ⟶ …………… + …………… ↓
26. Ammonium salts	NH₄Cl + NaOH ⟶ …………… + …………… + …………… [g]
	NH₄Cl + Ca(OH)₂ ⟶ …………… + …………… + …………… [g]

Answer

BASES — Ions present in bases
a. Alkali — dissociates yielding hydroxyl ions
16. Sodium hydroxide	NaOH [aq.] ⇌ *Na⁺* + *OH^–*
17. Ammonium hydroxide	NH₄OH [aq.] ⇌ *NH₄⁺* + *OH^–*
b. Classification
18. Monoacidic base [Acidity = 1 ]	KOH [aq.] ⇌ K⁺ + *OH^–*
19. Diacidic base [Acidity = 2]	Cu(OH)₂ [aq.] ⇌ *Cu²⁺* + *2OH^–*
c. Preparation of bases
20. From metals	4Na + O₂ ⟶ *2Na₂O*
21. From metallic oxides and metals	K₂O + H₂O ⟶ *2KOH*
	2K + 2H₂O ⟶ *2KOH* + H₂
22. From salts	AlCl₃ + 3NaOH ⟶ *3NaCl* + *Al(OH)₃* ↓
	FeSO₄ + 2NaOH ⟶ *Na₂SO₄* + *Fe(OH)₂* ↓
23. By thermal decomposition	ZnCO₃ ⟶ *ZnO* + *CO₂* [g]
	2Pb(NO₃)₂ ⟶ *2PbO* + *4NO₂* [g] + O₂ [g]
c. Properties of bases
24. Neutralizes acids	PbO + 2HNO₃ ⟶ *Pb(NO₃)₂* + *H₂O*
	Fe(OH)₂ + 2HCl ⟶ *FeCl₂* + *2H₂O*
Reaction with
25. Metallic salt solution	CuCl₂ + 2NaOH ⟶ *2NaCl* + *Cu(OH)₂* ↓
	FeCl₃ + 3NaOH ⟶ *3NaCl* + *Fe(OH)₃* ↓
26. Ammonium salts	NH₄Cl + NaOH ⟶ *NaCl* + *H₂O* + *NH₃* [g]
	2NH₄Cl + Ca(OH)₂ ⟶ *CaCl₂* + *2H₂O* + *2NH₃* [g]

Question 3

SALTS — Ions present in salts
27a. Normal salt [formation]	NaOH [excess] + H₂SO₄ ⟶ …………… + H₂O
27b. Acid salt [formation]	NaOH [insufficient] + H₂SO₄ ⟶ …………… + H₂O
Preparation of salts — General methods
Direct combination — Synthesis
28. Iron and Chloride — salt iron [III] Chloride	Fe + Cl₂ ⟶ ……………
29. Zinc and sulphur — salt zinc sulphide	Zn + S ⟶ ……………
Displacement — Action of dilute acid on active metals
30. Iron — salt iron [II] sulphate	Fe + H₂SO₄ ⟶ …………… + …………… [g]
31. Zinc — salt zinc sulphate	Zn + H₂SO₄ ⟶ …………… + …………… [g]
32. Magnesium — salt magnesium chloride	Mg + HCl ⟶ …………… + …………… [g]
Precipitation — by double decomposition of two salt solutions
33. Lead nitrate and sodium chloride	Pb(NO₃)₂ + NaCl ⟶ …………… + …………… ↓
34. Calcium chloride and sodium carbonate	CaCl₂ + Na₂CO₃ ⟶ …………… + …………… ↓
Neutralization — Action of dilute acid on insoluble base
35. Oxide — salt copper sulphate	CuO + H₂SO₄ ⟶ …………… + ……………
36. Hydroxide — salt copper sulphate	Cu(OH)₂ + H₂SO₄ ⟶ …………… + ……………
Neutralization — [Titration] Action of dilute acid on an alkali
37. Hydroxide — salt sodium chloride	NaOH + HCl ⟶ …………… + ……………
38. Hydroxide — salt ammonium chloride	NH₄OH + HCl ⟶ …………… + ……………
Action of dilute acid on carbonate & bicarbonate
39. Carbonate — salt lead nitrate	PbCO₃ + HNO₃ ⟶ …………… + …………… + …………… [g]
40. Carbonate — salt copper chloride	CuCO₃ + HCl ⟶ …………… + …………… + …………… [g]
41. Bicarbonate — salt potassium sulphate	KHCO₃ + H₂SO₄ ⟶ …………… + …………… + …………… [g]

Answer

SALTS — Ions present in salts
27a. Normal salt [formation]	2NaOH [excess] + H₂SO₄ ⟶ *Na₂SO₄* + 2H₂O
27b. Acid salt [formation]	NaOH [insufficient] + H₂SO₄ ⟶ *NaHSO₄* + H₂O
Preparation of salts — General methods
Direct combination — Synthesis
28. Iron and Chloride — salt iron [III] Chloride	2Fe + 3Cl₂ ⟶ *2FeCl₃*
29. Zinc and sulphur — salt zinc sulphide	Zn + S ⟶ *ZnS*
Displacement — Action of dilute acid on active metals
30. Iron — salt iron [II] sulphate	Fe + H₂SO₄ ⟶ *FeSO₄* + H₂ [g]
31. Zinc — salt zinc sulphate	Zn + H₂SO₄ ⟶ *ZnSO₄* + H₂ [g]
32. Magnesium — salt magnesium chloride	Mg + 2HCl ⟶ *MgCl₂* + H₂ [g]
Precipitation — by double decomposition of two salt solutions
33. Lead nitrate and sodium chloride	Pb(NO₃)₂ + 2NaCl ⟶ *2NaNO₃* + *PbCl₂* ↓
34. Calcium chloride and sodium carbonate	CaCl₂ + Na₂CO₃ ⟶ *2NaCl* + *CaCO₃* ↓
Neutralization — Action of dilute acid on insoluble base
35. Oxide — salt copper sulphate	CuO + H₂SO₄ ⟶ *CuSO₄* + *H₂O*
36. Hydroxide — salt copper sulphate	Cu(OH)₂ + H₂SO₄ ⟶ *CuSO₄* + *2H₂O*
Neutralization — [Titration] Action of dilute acid on an alkali
37. Hydroxide — salt sodium chloride	NaOH + HCl ⟶ *NaCl* + *H₂O*
38. Hydroxide — salt ammonium chloride	NH₄OH + HCl ⟶ *NH₄Cl* + *H₂O*
Action of dilute acid on carbonate & bicarbonate
39. Carbonate — salt lead nitrate	PbCO₃ + 2HNO₃ ⟶ *Pb(NO₃)₂* + *H₂O* + *CO₂* [g]
40. Carbonate — salt copper chloride	CuCO₃ + 2HCl ⟶ *CuCl₂* + *H₂O* + *CO₂* [g]
41. Bicarbonate — salt potassium sulphate	2KHCO₃ + H₂SO₄ ⟶ *K₂SO₄* + *2H₂O* + *2CO₂* [g]

2006

Question 1

Mention the colour changes observed when the following indicators are added to acids:

(i) Alkaline phenolphthalein solution.

(ii) Methyl orange solution

(iii) Neutral litmus solution

Answer

(i) Pink solution becomes colourless.

(ii) Orange solution changes to pink colour.

(iii) Purple solution changes to red colour.

Question 2

Which of the following hydroxides is not an alkali — [Choose from the choices A, B, C and D]

(A) ammonium hydroxide

(B) calcium hydroxide

(D) sodium hydroxide

Answer

Copper hydroxide [Cu(OH)₂] Reason — Copper hydroxide [Cu(OH)₂] is an example of insoluble base and it is not an alkali.

2007

Question 1

Complete the blanks from the list given:

Ammonia, Ammonium, Carbonate, Carbon dioxide, Hydrogen, Hydronium, Hydroxide, Precipitate, Salt, Water.

A solution X turns blue litmus red, so it must contain (i) …………… ions; another solution Y turns red litmus blue and therefore, must contain (ii) …………… ions. When solutions X and Y are mixed together the products will be a (iii) …………… and (iv) …………… . If a piece of magnesium were put into solution X, (v) …………… gas would be evolved.

Answer

A solution X turns blue litmus red, so it must contain (i) hydronium ions; another solution Y turns red litmus blue and therefore, must contain (ii) hydroxide ions. When solutions X and Y are mixed together the products will be a (iii) salt and (iv) water. If a piece of magnesium were put into solution X, (v) hydrogen gas would be evolved.

Question 2

Match the following:

Column A	Column B
1.Acid salt	A. Sodium potassium carbonate
2.Normal salt	B. Alum
	C. Sodium carbonate
	D. Sodium zincate
	E. Sodium hydrogen carbonate.

Answer

Column A	Column B
1.Acid salt	E. Sodium hydrogen carbonate.
2.Normal salt	C. Sodium carbonate

Question 3

Write balanced equation for formation of PbCl₂ from Pb(NO₃)₂ soln. and NaCl soln.

Answer

Pb(NO₃)₂ + 2NaCl ⟶ PbCl₂ + 2NaNO₃

2008

Question 1

What is the term defined : i) A base which is soluble in water.

Answer

Alkali is a base which is soluble in water.

2009

Question 1

The acid which contains four hydrogen atoms —

Formic acid
Sulphuric acid
Nitric acid
Acetic acid

Answer

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

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

Solution A is a strong acid
Solution B is a weak acid
Solution C is a strong alkali

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

(ii) Which solution will give a gelatinous white precipitate with zinc sulphate solution? The precipitate disappears when an excess of the solution is added.

(iii) Which solution could be glacial acetic acid solution?

(iv) Give example of a soln. of a weak alkali.

Answer

(i) 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]

(ii) 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]

(iii) Solution B — weak acid
Reason — Anhydrous acetic acid on cooling forms crystals of glacial acetic acid and acetic acid is a weak acid.

(iv) Ammonium hydroxide (NH₄OH)

Question 4

Write the equation[s] for the reaction[s] to prepare lead sulphate from lead carbonate.

Answer

PbCO₃ + 2HNO₃ ⟶ Pb(NO₃)₂ + H₂O + CO₂

Pb(NO₃)₂ + Na₂SO₄ ⟶ PbSO₄ + 2NaNO₃

Question 5

Define the following terms — Neutralization

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)]

2010

Question 1

A: Nitroso Iron [II] sulphate

B: Iron [III] chloride

C: Chromium sulphate

D: Lead [II] chloride

E: Sodium chloride.

Select from A, B, C, D and E —

(i) A compound soluble in hot water but insoluble in cold water.

(ii) A compound which in the aqueous solution state, is neutral in nature.

Answer

(i) D: Lead [II] chloride

(ii) E: Sodium chloride

Question 2

Select the correct answer from A, B, C and D –

(i) A weak organic acid is:

Formic acid
Sulphuric acid
Nitric acid
Hydrochloric acid

(ii) A complex salt is :

Zinc sulphate
Sodium hydrogen sulphate
Iron (II) ammonium sulphate
Tetrammine copper (II) sulphate

Answer

(i) Formic acid

(ii) Tetrammine copper (II) sulphate

Question 3

Give an equation for the conversions

(i) ZnSO₄ to ZnCO₃

(ii) ZnCO₃ to Zn(NO₃)₂

Answer

(i) ZnSO₄ + (NH₄)₂CO₃ ⟶ (NH₄)₂SO₄ + ZnCO₃

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

Question 4

NaOH soln.
Weak acid
Dil. H₂SO₄

Select the one which contains solute ions and molecules.

Answer

Weak acid
Reason — An acid which dissociates only partially in aqueous solution thereby producing a low concentration of hydrogen [H⁺] ions [or H₃O⁺ ions] is a weak acid.

Example — CH₃COOH ⇌ CH₃COO^– + H⁺ [contains molecules and ions]

Question 5

Give balanced equation/s for the preparation of the following salts:

Copper [II] sulphate from CuO.
Iron [III] chloride from Fe.
K₂SO₄ from KOH soln.
Lead [II] chloride from PbCO₃ [give two equations].

Answer

CuO + H₂SO₄ ⟶ CuSO₄ + H₂O
2Fe + 3Cl₂ ⟶ 2FeCl₃
2KOH + H₂SO₄ [dil.] ⟶ K₂SO₄ + 2H₂O
PbCO₃ + 2HNO₃ ⟶ Pb(NO₃)₂ + H₂O + CO₂
Pb(NO₃)₂ + 2NaCl ⟶ 2NaNO₃ + PbCl₂

2011

Question 1

Write the balanced chemical equation : Lead nitrate solution is added to sodium chloride solution

Answer

Pb(NO₃)₂ + 2NaCl ⟶ PbCl₂ + 2NaNO₃

Question 2

Name the method used from the list:

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

For preparation of the following salts –

(i) Sodium nitrate

(ii) Iron (III) chloride

(iii) Lead chloride

(iv) Zinc sulphate

(v) Sodium hydrogen sulphate.

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

2012

Question 1

Match the following i.e.,

(1) Acid salt

(2) Double salt — with the correct choice from — A and B

A : Ferrous ammonium sulphate

B : Sodium hydrogen sulphate

Answer

Acid salt — B : Sodium hydrogen sulphate
Double salt — A : Ferrous ammonium sulphate

2013

Question 1

Select the word/s given below which are required to correctly complete the blanks — [ammonia, ammonium, carbonate, carbon dioxide, hydrogen, hydronium, hydroxide, precipitate, salt water] :

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

(ii) When solution M and O are mixed together, the products will be (iii) …………… and (iv) …………… .

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

Answer

(i) A solultion M turns blue litmus red, so it must contain (i) hydronium ions ; another solution O turns red litmus blue and hence, must contain, (ii) hydroxide ions.

(ii) When solution M and O are mixed together, the products will be (iii) salt and (iv) water.

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

Question 2

Give a suitable chemical term for:

(i) A salt formed by incomplete neutralisation of an acid by a base.

(ii) A definite number of water molecules bound to some salts.

Answer

(i) Acid salt

(ii) Water of crystallization

Question 3

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.

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 4

Identify: An acid which is present in vinegar.

Answer

Acetic acid

2014

Question 1

Fill in the blank from the choices given:

The basicity of acetic acid is …………… [3, 1, 4].

Answer

The basicity of acetic acid is 1.

Question 2

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

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 3

State the inference drawn from the observation:

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

Answer

Salt S is Copper sulphate CuSO₄

CuO + H₂SO₄ (dil.) ⟶ CuSO₄ + H₂O

Question 4

Give balanced chemical equations for the preparation of the following salts:

Lead sulphate — from lead carbonate.
Sodium sulphate — using dilute sulphuric acid.
Copper chloride — using copper carbonate.

Answer

Lead sulphate from lead carbonate.
PbCO₃ + 2HNO₃ ⟶ Pb(NO₃)₂ + H₂O + CO₂
Pb(NO₃)₂ + Na₂SO₄ ⟶ 2NaNO₃ + PbSO₄
Sodium sulphate using dilute sulphuric acid.
Na₂CO₃ + H₂SO₄(dil.) ⟶ Na₂SO₄ + H₂O+ CO₂
Copper chloride using copper carbonate.
CuCO₃ + 2HCl (dil) ⟶ CuCl₂ + H₂O + CO₂

2015

Question 1

Give a balanced chemical equation for the following conversion.

Fe ⟶ FeCl₃

Answer

2Fe + 3Cl₂ ⟶ 2FeCl₃

Question 2

From the list of salts — AgCl, MgCl₂, NaHSO₄, PbCO₃
Choose the salt that most appropriately fits the description given below :
An insoluble chloride.

Answer

AgCl

Question 3

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

Answer

SO₂

The following reaction takes place.

SO₂ + H₂O ⟶ H₂SO₃

2016

Question 1

Fill in the blank:
Higher the pH value of a solution, the more …………… [acidic/alkaline] it is.

Answer

Higher the pH value of a solution, the more alkaline it is.

Question 2

Match the following salts given below:

(i) Pb(NO₃)₂ from PbO

(ii) MgCl₂ from Mg

(iii) FeCl₃ from Fe

(iv) NaNO₃ from NaOH

(v) ZnCO₃ from ZnSO₄

With their correct method of preparation from: A, B, C, D and E.

(A) Simple displacement

(B) Titration

(D) Precipitation

(E) Combination

Answer

(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

2017

Question 1

Fill in the blanks from the choices given in brackets —

When a metallic oxide is dissolved in water, the solution formed has a high concentration of …………… ions. [H⁺, H₃O⁺, OH^–]

Answer

When a metallic oxide is dissolved in water, the solution formed has a high concentration of OH^– ions.

Question 2

Choose the correct answer from the options —

(i) To increase the pH value of a neutral solution, we should add :

An acid
An acid salt
An alkali
A salt

(ii) Anhydrous iron [III] chloride is prepared by:

Direct combination
Simple displacement
Decomposition
Neutralization

Answer

(i) An alkali
Reason — The pH of alkali solutions is more than 7 therefore in order to increase the pH value of a neutral solution, an alkali should be added.

(ii) Direct combination
Reason — Anhydrous iron [III] chloride is prepared by direct combination of iron and chloride as follows —
2Fe + 3Cl₂ ⟶ 2FeCl₃

Question 3

Write a balanced chemical equation for the preparation of each of the following salts:

(i) Copper carbonate

(ii) Ammonium sulphate crystals.

Answer

(i) CuSO₄ + Na₂CO₃ ⟶ Na₂SO₄ + CuCO₃

(ii) 2NH₄OH + H₂SO₄ ⟶ (NH₄)₂SO₄ + 2H₂O

2018

Question 1

Give one word or a phrase for the statement :
The property by which certain hydrated salts, when left exposed to the atmosphere, lose their water of crystallization and crumble into powder.

Answer

Efflorescence

Question 2

State one relevant observation for the following :
Anhydrous calcium chloride is exposed to air for some time.

Answer

It absorbs moisture from the atmosphere, dissolve in the same and change into a solution. This property is known as deliquescence

Question 3

Fill in the blank with the correct choice given in the bracket —
The salt prepared by the method of direct combination is …………… [iron [II] chloride / iron [III] chloride]

Answer

The salt prepared by the method of direct combination is iron [III] chloride

Question 4

Three solutions P, Q, and R have pH value of 3.5, 5.2 and 12.2 respectively. State which one of these is a:

(i) weak acid

(ii) strong alkali

Answer

(i) Q
Reason — On a pH scale, acids have pH less than 7 whereas weak acids have pH towards 7. Hence, Q will be a weak acid with pH 5.2 .

(ii) R
Reason — On a pH scale, alkali have pH more than 7 and alkalinity increases as the pH value moves away from 7. Hence, R will be a strong alkali with pH 12.2 .

Question 5

Write a balanced equation for the preparation of each of the following salts :

(i) Copper [II] sulphate from copper carbonate

(ii) Zinc carbonate from zinc sulphate

Answer

(i) CuCO₃ + H₂SO₄ ⟶ CuSO₄ + H₂O + CO₂

(ii) ZnSO₄ + (NH₄)₂CO₃ ⟶ (NH₄)₂SO₄ + ZnCO₃

2019

Question 1

Give the appropriate term defined by the statement given :
The substance that releases hydronium ion as the only positive ion when dissolved in water.

Answer

Acid
Reason — An acid is a compound which when dissolved in water yields hydronium ions [H₃O⁺] as the only positively charged ion.

HCl (aq) ⇌ H⁺ + Cl^–

H⁺ + H₂O ⇌ H₃O⁺ [hydronium ion]

HCl + H₂O ⇌ H₃O⁺ + Cl^–

Question 2

The pH values of three solutions A, B, C are given .

Solution A : pH value 12

Solution B : pH value 2

Solution C : pH value 7

Answer the following questions :

(i) Which solution will have no effect on litmus solution.

(ii) Which solution will liberate CO₂ when reacted with sodium carbonate.

(iii) Which solution will turn red litmus solution blue.

Answer

(i) Solution C : pH value 7

(ii) Solution B : pH value 2

(iii) Solution A : pH value 12

Question 3

Choose the method of preparation of the following salts, from the methods given in the list:

List —
A: Neutralization
B: Precipitation
C: Direct combination
D: Substitution

(i) Lead chloride
(ii) Iron [II] Sulphate
(iii) Sodium nitrate
(iv) Iron [III] chloride

Answer

(i) Lead chloride — B: Precipitation

(ii) Iron [II] Sulphate — D: Substitution

(iii) Sodium nitrate — A: Neutralization

(iv) Iron [III] chloride — C: Direct combination

2020

Question 1

Fill in the blanks from the choices given : A salt prepared by displacement reaction is …………… [Ferric chloride, ferrous chloride, silver chloride]

Answer

Ferric chloride

Question 2

Complete the following by selecting the correct options from the choices :
pH of acetic acid is greater than dilute sulphuric acid. So, acetic acid contains …………… concentration of H⁺ ions. [greater, same, low]

Answer

pH of acetic acid is greater than dilute sulphuric acid. So, acetic acid contains low concentration of H⁺ ions.

Question 3

Differentiate between the following pairs based on the information given in the brackets :
Acid and alkali [formation of type of ions]

Answer

Acid	Alkali
An acid is a compound which when dissolved in water yields hydronium ions [H₃O⁺] as the only positively charged ion.	An alkali is a compound which when dissolved in water yields hydroxyl ions [OH^–] as the only negatively charged ions.

Question 4

Write balanced chemical equations, for the preparation of given salts (i) to (iii) by using the methods A to C respectively.

A: Neutralization
B: Precipitation
C: Titration

(i) Copper sulphate
(ii) Zinc carbonate
(iii) Ammonium sulphate

Answer

Preparation of copper sulphate by neutralization
CuO + H₂SO₄ ⟶ CuSO₄ + H₂O
Preparation of zinc carbonate by precipitation
Zn(NO₃)₂ + Na₂CO₃ ⟶ 2NaNO₃ + ZnCO₃
Preparation of ammonium sulphate by titration
2NH₄OH + H₂SO₄ ⟶ (NH₄)₂SO₄ + 2H₂O

Additional Questions

Question 1

Define the following as per ionic theory with examples and ionic equations wherever relevant :

(i) acid (ii) base (iii) alkali (iv) neutralization

Answer

(i) Acid — An acid is a compound which when dissolved in water yields hydronium ions [H₃O⁺] as the only positively charged ion.

HCl (aq) ⇌ H⁺ + Cl^–

H⁺ + H₂O ⇌ H₃O⁺ [hydronium ion]

HCl + H₂O ⇌ H₃O⁺ + Cl^–

(ii) Base — A base is a compound which reacts with hydronium ions of an acid to give salt and water only.

CuO + 2HCl ⟶ CuCl₂ + H₂O

Cu(OH)₂ + H₂SO₄ ⟶ CuSO₄ + 2H₂O

Bases are oxides or hydroxides of a metal [including ammonium hydroxide]
Examples of insoluble bases [i.e., not alkalis] — ZnO, PbO, CuO, Fe(OH)₂, Pb(OH)₂, Cu(OH)₂

(iii) Alkali — An alkali is a compound which when dissolved in water yields hydroxyl ions [OH^–] as the only negatively charged ions.

NaOH [aq.] ⇌ Na⁺ + OH^– [Hydroxyl or hydroxide ion]

Alkali is a base, soluble in water. [All alkalis are bases, but all bases are not alkalis.]

Examples of soluble bases [i.e., alkalis] — KOH, NaOH [strong alkalis] , Ca(OH)₂, NH₄OH (weak alkalis).

(iv) 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

Differentiate between:

(i) Organic and inorganic acids.

(ii) Hydracids and oxyacids with examples.

Answer

(i) Difference between organic and inorganic acids are as follows :

Organic acids	Inorganic acids
Acids derived from plants, e.g., citric acid, tartaric acid, acetic acid.	Acids derived from minerals e.g. HCl, H₂SO₄, HNO₃

(ii) Difference between hydracids and oxyacids are as follows :

Hydracids	Oxyacids
Acids containing hydrogen and a non-metallic element other than oxygen, e.g. HCl, HBr, HI.	Acids containing hydrogen, another element and oxygen, e.g. HNO₃, H₂SO₄.

Question 3

State on what basis does the strength of an acid and an alkali depend on.

Answer

Strength of acids depends on the concentration of hydronium ion [H₃O⁺] present in an aqueous solution of an acid.

Strength of alkali depends on the concentration of the hydroxyl ions [OH^–] present in an aqueous solution of the alkali.

Question 4

Differentiate between (i) strong and weak acid (ii) strong and weak alkali with suitable examples and ionic equations.

Answer

(i) Differences between strong and weak acid are as follows :

Strong Acid	Weak Acid
Strong Acid is an acid which dissociates almost completely in aqueous solution there by producing a high concentration of hydrogen [H⁺] ions [or H₃O⁺ ions]	Weak Acid is an acid which dissociates only partially in aqueous solution thereby producing a low concentration of hydrogen [H⁺] ions [or H₃O⁺ ions].
HNO₃ + H₂O ⇌ H₃O⁺ + NO₃^– [contains almost only ions]	CH₃COOH ⇌ CH₃COO^– + H⁺ [contains molecules and ions]
Examples : Hydrochloric, Sulphuric and Nitric acid.	Examples : Acetic, citric, carbonic, and formic acid.

(ii) Differences between strong alkali and and weak alkali are as follows :

Strong alkali	Weak Alkali
Strong Alkali is an alkali which dissociates almost completely in aqueous solution thereby producing a high concentration of hydroxyl [OH^–] ions.	Weak Alkali is an alkali which dissociates only partially in aqueous solution thereby producing a low concentration of hydroxyl [OH^–] ions.
NaOH [aq.] ⇌ Na⁺ + OH^– [contains almost only ions]	NH₄OH [aq.] ⇌ NH₄⁺ + OH^– [contains molecules and ions]
Examples : Lithium, Sodium and Potassium hydroxide	Examples : Ammonium hydroxide and Calcium hydroxide.

Question 5

Name the ions formed when — HCl; HNO₃; H₂SO₄; CH₃COOH; NaOH and NH₄OH ionise in aq. soln.

Answer

(i) When HCl is dissolved in water, it is ionised into hydrogen ion [or H₃O⁺ ion] and chloride ion.

HCl ⟶ H⁺ + Cl^–

The H⁺ cannot exist independently, therefore, it combines with water molecule to form hydronium ion (H₃O⁺)

H⁺ + H₂O ⟶ H₃O⁺

(ii) When HNO₃ is dissolved in water, it is ionised into hydronium ion and nitrate ion.

HNO₃ ⟶ H⁺ + NO₃^–

H⁺ + H₂O ⟶ H₃O⁺

(iii) When H₂SO₄ is dissolved in water, it is ionised into hydronium ion and sulphate ion.

H₂SO₄ ⟶ 2H⁺ + SO₄^2-

H⁺ + H₂O ⟶ H₃O⁺

(iii) When CH₃COOH is dissolved in water, it is ionised into hydronium ion and acetate ion.

CH₃COOH ⟶ CH₃COO^– + H⁺

H⁺ + H₂O ⟶ H₃O⁺

(iii) When NaOH is dissolved in water, it is ionised into sodium ion and hydroxyl ion.

NaOH ⟶ Na⁺ + OH^–

(iv) When NH₄OH is dissolved in water, it is ionised into ammonium ion and hydroxyl ion.

NH₄OH ⟶ NH₄⁺ + OH^–

Question 6

State giving reasons which is a stronger acid — dil. HCl or conc. H₂CO₃.

Answer

Dilute HCl is a stronger acid than concentrated H₂CO₃
Reason — HCl dissociates almost completely in aqueous solution and produces a high concentration of H⁺ ions and Cl^– ions, hence is a strong acid. Whereas, H₂CO₃ is a weak acid because it dissociates partially yielding H⁺ ions and bicarbonate HCO₃^– ion and hence, contains ions as well as molecules. Therefore, dil. HCl is a stronger acid than conc. H₂CO₃.

Question 7

State why the basicity of acetic acid is one and acidity of calcium hydroxide is two.

Answer

Basicity of acid — is the number of hydrogen ions [H⁺] which can be produced per molecule of the acid in aq. soln. Acetic acid [CH₃COOH] ionises in aq. soln. and gives one hydrogen ion per molecule of the acid, hence acetic acid is monobasic i.e., it’s basicity is one.

Acidity of base — is the number of hydroxyl ions [OH^–] which can be produced per molecule of the base in aq. soln. Calcium hydroxide Ca(OH)₂ ionises in aq. soln. and gives two hydroxyl ions per molecule of the base, hence calcium hydroxide is a diacidic base i.e., it’s acidity is two.

Question 8

Give three reasons with equations wherever required, why Sulphuric acid is a dibasic acid.

Answer

Sulphuric acid (H₂SO₄) is a dibasic acid as :

It ionises in aq. soln. to produce two hydrogen ions per molecule of the acid.
It dissociate in two steps in aq. soln. as shown below:
H₂SO₄ + H₂O ⇌ H₃O⁺ + HSO₄^–
HSO₄^– + H₂O ⇌ H₃O⁺ + SO₄^2-
H₂SO₄ + 2H₂O ⇌ 2H₃O⁺ + SO₄^2-
It contains two replaceable hydrogen ions per molecule of the acid so forms two types of salt [acid and normal salt] :
NaOH + H₂SO₄ ⟶ NaHSO₄ (Acid Salt) + H₂O
2NaOH + H₂SO₄ ⟶ Na₂SO₄ (Normal Salt) + 2H₂O

Question 9

State how acids are defined as per Arrhenius’s and Lowry – Bronsted’s theory.

Answer

Arrhenius Theory — Acids are substances which dissociate in aqueous solution to give H⁺ ions.
Strong acids dissociate almost completely, while weak acids dissociate partially.

Lowry – Bronsted’s theory — Acids are proton donors and bases are proton acceptors [proton = H⁺].
HCl [aq.] ⟶ H⁺ + Cl^– [acid – proton donors] NH₃ + H⁺ ⟶ NH₄⁺ [bases – proton acceptors]

Question 10

Oxygen atom in water has two ‘lone pair of electrons‘. Explain the meaning of the term in italics. With the help of an electron dot diagram show the formation of hydronium ion and ammonium ion from a water molecule and an ammonia molecule respectively.

Answer

Oxygen atom in water has two ‘lone pair of electrons‘ implies that two pairs of electrons on oxygen are not shared with any other atom as shown below:

Formation of hydronium ion

Oxygen atom in water has two lone pair of electrons. Explain the meaning of the term in italics. With the help of an electron dot diagram show the formation of hydronium ion and ammonium ion from a water molecule and an ammonia molecule respectively. Acids, Bases and Salts, Simplified Chemistry Dalal Solutions ICSE Class 10

Formation of ammonium ion

Question 11

State how you would obtain:

Sulphuric acid from an acidic oxide
KOH from a basic oxide.

Answer

Acidic oxides dissolve in water to give an acid.
SO₃ + H₂O ⟶ H₂SO₄
Basic oxides [soluble] dissolve in water to give a base i.e., alkali.
K₂O + H₂O ⟶ 2KOH

Question 12

State two chemical properties each with equations of a solution containing

(i) H⁺ ions

(ii) OH^– ions

Answer

(i) Chemical properties of a solution containing H⁺ (acids) are as follows —

Neutralization — acids neutralizes base to give salt and water only.
Example : CuO + H₂SO₄ ⟶ CuSO₄ + H₂O
Reaction with active metals — Acids react with active metals [e.g., Mg, Al, Zn, Fe] to liberate hydrogen.
Example : Zn + 2HCl ⟶ ZnCl₂ + H₂

(ii) Chemical properties of a solution containing OH^– (bases/alkalis) are as follows —

Neutralization — Alkalis neutralize acids to form salt and water.
Example :
Ca(OH)₂ + 2HCl ⟶ CaCl₂ + 2H₂O
Reaction with metallic salt — Alkalis react with certain matallic salt solutions to precipitate insoluble hydroxide.
Example :
FeCl₃ + 3NaOH ⟶ 3NaCl + Fe(OH)₃ ↓ red brown ppt.