NCERT Exemplar Chapter 2 Acids, Bases and Salts Class 10 Science Solutions

NCERT Exemplar Class 10 Science Chapter 2 Acids, Bases and Salts Solutions

NCERT Exemplar Solutions for Class 10 Science Chapter 2 Acids, bases and salts covers all the important questions and answers as well as advanced level questions. It will teach students about the chemical properties of aids, bases, salts, common properties of acids and bases and reaction between acids and bases.

The NCERT Exemplar solutions for class 10 science is very important for board exams. NCERT Exemplar Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts is provided by our experts. They prepared the best solutions which help the students in understanding the problems in an easy way. This chapters also covers the other topics like neutralization reactions, chemicals obtained from salts, reactivity series, metallic oxides and non-metallic oxides.

Chapter Name	Chapter 2 Acids, Bases and Salts
Book Title	NCERT Exemplar for Class 10 Science
Related Study	NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts Revision Notes for Class 10 Science Chapter 2 Acids, Bases and Salts MCQ for Class 10 Science Chapter 2 Acids, Bases and Salts Important Questions for Class 10 Science Chapter 2 Acids, Bases and Salts
Topics Covered	MCQ Short Answers Questions Long Answers Questions

NCERT Exemplar Solutions for Chapter 2 Acids, Bases and Salts Class 10 Science

Multiple Choice Questions

1. What happens when a solution of an acid is mixed with a solution of a base in a test tube?
(i) The temperature of the solution increases
(ii) The temperature of the solution decreases
(iii) The temperature of the solution remains the same
(iv) Salt formation takes place
(a) (i) only
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (i) and (iv)

Solution

(d) (i) and (iv)

Neutralization reaction takes place when acid is mixed with a solution of base. Neutralization is an exothermic reaction which results in the formation salt.

2. An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?
(a) Baking powder
(b) Lime
(c) Ammonium hydroxide solution
(d) Hydrochloric acid

Solution

(d) Hydrochloric acid

The solution is basic in nature if it turns red litmus to blue. This effect can be neutralized by adding an acid.

3. During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to
(a) absorb the evolved gas
(b) moisten the gas
(c) absorb moisture from the gas
(d) absorb Cl– ions from the evolved gas

Solution

(c) absorb moisture from the gas

Calcium has property to absorb moisture hence it is a good dehydrating agent. This makes it usable as a desiccant to dry gases and hydrocarbons in the industries.

4. Which of the following salts does not contain water of crystallisation ? 
(a) Blue vitriol 
(b) Baking soda 
(c) Washing soda 
(d) Gypsum

Solution

(b) Baking soda 

Baking sodas is white amorphous powder whereas other salts given are crystalline in nature.

5. Sodium carbonate is a basic salt because it is a salt of
(a) strong acid and strong base
(b) weak acid and weak base
(c) strong acid and weak base
(d) weak acid and strong base

Solution

(d) weak acid and strong base

Weak acid and strong base forms a strong salt. In this case sodium is a strong base and carbonate is a weak acid.

6. Calcium phosphate is present in tooth enamel. Its nature is 
(a) basic 
(b) acidic 
(c) neutral 
(d) amphoteric

Solution

(a) basic

Calcium phosphate contains phosphate ions which are strong bases. Phosphate ions form a strong salt. Therefore, calcium phosphate is basic in nature.

7. A sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish - orange. Which of the following would change the colour of this pH paper to greenish-blue?
(a) Lemon juice
(b) Vinegar
(c) Common salt
(d) An antacid

Solution

(d) An antacid

Sample solution turn pH paper yellowish-orange. This confirms the acidic nature of the sample. To change the color to greenish-blue we have to add an antacid.

8. Which of the following gives the correct increasing order of acidic strength

(a) Water < Acetic acid < Hydrochloric acid
(b) Water < Hydrochloric acid< Acetic acid
(c) Acetic acid< Water < Hydrochloric acid
(d) Hydrochloric acid< Water<Acetic acid

Solution

(a) Water < Acetic acid < Hydrochloric acid

In pure form water is neutral. Acetic acid is weak acid as it is an organic acid whereas hydrochloric acid is a strong acid.

9. If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done?
(a) Wash the hand with saline solution
(b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogencarbonate
(c) After washing with plenty of water apply solution of sodium hydroxide on the hand
(d) Neutralise the acid with a strong alkali

Solution

(b) Wash the hand immediately with plenty of water and apply a paste of sodium hydrogencarbonate

Washing the hand with plenty of water will reduce the concentration of the acid. Further traces of the acid can be neutralized by applying a paste of Hydrogen carbonate which is basic. NaOH is also a base but it is corrosive in nature and hence should not be used.

10. Sodium hydrogencarbonate when added to acetic acid evolves a gas. Which of the following statements are true about the gas evolved?
(i) It turns lime water milky
(ii) It extinguishes a burning splinter
(iii) It dissolves in a solution of sodium hydroxide
(iv) It has a pungent odour 

(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (ii), (iii) and (iv)
(d) (i) and (iv)

Solution

(a) (i) and (ii)

Carbon dioxide gas is evolved when Sodium hydrogen carbonate reacts with acetic acid. Carbon dioxide gas turns lime water milky and extinguishes a burning splinter.

11. Common salt besides being used in kitchen can also be used as the raw material for making
(i) washing soda
(ii) bleaching powder
(iii) baking soda
(iv) slaked lime 

(a) (i) and (ii)
(b) (i), (ii) and (iv)
(c) (i) and (iii)
(d) (i), (iii) and (iv)

Solution

(a) (i) and (ii)

12. One of the constituents of baking powder is sodium hydrogencarbonate, the other constituent is
(a) hydrochloric acid
(b) tartaric acid
(c) acetic acid
(d) sulphuric acid

Solution

(b) tartaric acid

A mild edible acid along with Sodium Hydrogen Carbonate is used to prepare baking powder. Therefore acetic acid or citric acid can also be used in place of tartaric acid.

13. To protect tooth decay we are advised to brush our teeth regularly. The nature of the tooth paste commonly used is
(a) acidic
(b) neutral
(c) basic
(d) corrosive

Solution

(c) basic

Because of bacterial activity in mouth, teeth will be acidic in nature. To neutralize the acid, toothpaste must be basic in nature.

14. Which of the following statements is correct about an aqueous solution of an acid and of a base?
(i) Higher the pH, stronger the acid
(ii) Higher the pH, weaker the acid
(iii) Lower the pH, stronger the base
(iv) Lower the pH, weaker the base

(a) (i) and (iii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)

Solution

On a pH scale, for acids pH is below 7. Lower the pH, stronger will be acid and similarly bases are those whose pH is more than 7. Higher the pH stronger will be the base.

15. The pH of the gastric juices released during digestion is
(a) less than 7
(b) more than 7
(c) equal to 7
(d) equal to 0

Solution

(a) less than 7

The pH must be below 7 to ensure easy breakdown of food particles. Thus the pH of stomach juices is usually 3.

16. Which of the following phenomena occur, when a small amount of acid is added to water?
(i) Ionisation
(ii) Neutralisation
(iii) Dilution
(iv) Salt formation 

(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (ii) and (iv)

Solution

(b) (i) and (iii)

17. Which one of the following can be used as an acid–base indicator by a visually impared student?
(a) Litmus
(b) Turmeric
(c) Vanilla essence
(d) Petunia leaves

Solution

(c) Vanilla essence

Vanilla essence can be used as an olfactory indicator hence it can be used as acid base indicator by visually impaired students.

18. Which of the following substance will not give carbon dioxide on treatment with dilute acid?
(a) Marble
(b) Limestone
(c) Baking soda
(d) Lime 

Solution

(d) Lime 

Marble, limestone and baking soda, all have carbonates and thus produces CO₂ gas. Lime on the other hand contains hydroxide which will not produce CO₂.

19. Which of the following is acidic in nature?
(a) Lime juice
(b) Human blood
(c) Lime water
(d) Antacid

Solution

(a) Lime juice 

Lime juice contains citric acid in it. Therefore it is acidic in nature.

20. In an attempt to demonstrate electrical conductivity through an electrolyte, the following apparatus (Figure 2.1) was set up. Which among the following statement(s) is(are) correct?
(i) Bulb will not glow because electrolyte is not acidic
(ii) Bulb will glow because NaOH is a strong base and furnishes ions for conduction.
(iii) Bulb will not glow because circuit is incomplete
(iv) Bulb will not glow because it depends upon the type of electrolytic solution 

(a) (i) and (iii)
(b) (ii) and (iv)
(c) (ii) only
(d) (iv) only

Solution

(c) (ii) only

21. Which of the following is used for dissolution of gold?
(a) Hydrochloric acid
(b) Sulphuric acid
(c) Nitric acid
(d) Aqua regia

Solution

(d) Aqua regia

Gold is a noble metal and thus it will not react with strong acids. Therefor eaqua regia which is a mixture of Nitric and Hydrochloric acid in the ratio 1:3 is used for dissolution of gold.

22. Which of the following is not a mineral acid?
(a) Hydrochloric acid
(b) Citric acid
(c) Sulphuric acid
(d) Nitric acid

Solution

(b) Citric acid 

Citric acid is an organic acid. 

23. Which among the following is not a base?
(a) NaOH
(b) KOH
(c) NH₄OH
(d) C₂H₅OH

Solution

(d) C₂H₅OH

C₂H₅OH is an alcohol not a base. 

24. Which of the following statements is not correct?
(a) All metal carbonates react with acid to give a salt, water and carbon dioxide
(b) All metal oxides react with water to give salt and acid
(c) Some metals react with acids to give salt and hydrogen
(d) Some non metal oxides react with water to form an acid

Solution

(b) All metal oxides react with water to give salt and acid 

Metal oxides are basic in nature therefore they give alkaline solution when dissolved in water.

25. Match the chemical substances given in Column (A) with their appropriate application given in Column (B)

Column (A)	Column (B)
(A) Bleaching powder	(i) Preparation of glass
(B) Baking soda	(ii) Production of H2 and Cl2
(C) Washing soda	(iii) Decolourisation
(D) Sodium chloride	(iv) Antacid

(a) A—(ii), B—(i), C—(iv), D—(iii)
(b) A—(iii), B—(ii), C—(iv), D—(i)
(c) A—(iii), B—(iv), C—(i), D—(ii)
(d) A—(ii), B—(iv), C—(i), D—(iii)

Solution

(c) A—(iii), B—(iv), C—(i), D—(ii)

26. Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained? (You may use colour guide given in Figure 2.2

(a) Red
(b) Yellow
(c) Yellowish green
(d) Blue

Solution

(c) Yellowish green

Neutralization reaction takes place between HCL and NaOH solution. Hence pH will remain neutral that is in the yellowish green zone of pH paper.

27. Which of the following is(are) true when HCl (g) is passed through water?
(i) It does not ionise in the solution as it is a covalent compound.
(ii) It ionises in the solution
(iii) It gives both hydrogen and hydroxyl ion in the solution
(iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule.

(a) (i) only
(b) (iii) only
(c) (ii) and (iv)
(d) (iii) and (iv)

Solution

(c) (ii) and (iv) 

HCl ionizes completely in water to produce Hydrogen as HCl is a strong acid. Hydrogen thus produced combine with water molecules to give Hydronium ions. 

28. Which of the following statements is true for acids?
(a) Bitter and change red litmus to blue
(b) Sour and change red litmus to blue
(c) Sour and change blue litmus to red
(d) Bitter and change blue litmus to red

Solution

(c) Sour and change blue litmus to red 

29. Which of the following are present in a dilute aqueous solution of hydrochloric acid ?
(a) H₃O⁺ + Cl^-
(b) H₃O⁺ + OH^-
(c) Cl^- + OH^-
(d) unionised HCl 

Solution

(a) H₃O⁺ + Cl^-

Acid produces hydrogen which combines with water molecule to produce Hydronium ions.

30. Identify the correct representation of reaction occurring during chloralkali process
(a) 2NaCl(l) + 2H₂O(l) → 2NaOH(l) + Cl₂(g) + H₂(g)
(b) 2NaCl(aq) + 2H₂O(aq) → 2NaOH(aq) + Cl₂(g) + H₂(g)
(c) 2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl₂(aq) + H₂(aq)

(d) 2NaCl (aq) + 2H₂O (l) → 2NaOH (aq) + Cl₂(g) + H₂(g)

Solution

(d) 2NaCl (aq) + 2H₂O (l) → 2NaOH (aq) + Cl₂(g) + H₂(g)

Short Answer Questions 

 

31. Match the acids given in Column (A) with their correct source given in Column (B) 

Column (A)	Column (B)
(a) Lactic acid	(i) Tomato
(b) Acetic acid	(ii) Lemon
(c) Citric acid	(iii) Vinegar
(d) Oxalic acid	(iv) Curd

Solution

Column (A)	Column (B)
(a) Lactic acid	(i) Tomato
(b) Acetic acid	(ii) Lemon
(c) Citric acid	(iii) Vinegar
(d) Oxalic acid	(iv) Curd

32. Match the important chemicals given in Column (A) with the chemical formulae given in Coumn (B)

Column (A)	Column (B)
(a) Plaster of Paris	(i) Ca(OH)2
(b) Gypsum	(ii) CaSO4. ½ H2O
(c) Bleaching Powder	(iii) CaSO4.  2H2O
(d) Slaked Lime	(iv) CaOCl2

Solution 

Column (A)	Column (B)
(a) Plaster of Paris	(ii) CaSO4. ½ H2O
(b) Gypsum	(iii) CaSO4.  2H2O
(c) Bleaching Powder	(iv) CaOCl2
(d) Slaked Lime	(i) Ca(OH)2

33. What will be the action of the following substances on litmus paper? Dry HCl gas, Moistened NH₃ gas, Lemon juice, Carbonated soft drink, Curd, Soap Solution.

Solution

• Dry HCI gas: It will show no effect on litmus paper as no ionization will occur in gaseous state.
• Moistened NH₃ gas: It is alkaline in nature so red litmus will turn blue.
• Lemon Juice: It contains citric acid therefore it turns blue litmus to red.
• Carbonated soft drinks: They have carbonic acid which is a weak acid and can turns blue litmus to red.
• Curd: It contains lactic acid so blue litmus will turn red.
• Soap solution: They are alkaline in nature and can turn red litmus to blue.

34. Name the acid present in ant sting and give its chemical formula. Also give the common method to get relief from the discomfort caused by the ant sting.

Solution

Methanoic acid (formic acid)is present in ant sting. The chemical formula is HCOOH. One should apply any available basic salt e.g., baking soda (NaHCO₃) on it to get relief.

35. What happens when nitric acid is added to egg shell? 

Solution

When nitric acid is added to it, carbon dioxide gas is evolved as egg shells contain calcium carbonate.
The reaction can be given as:
CaCO₃ + 2HNO₃ → Ca (NO₃)₂ + H₂O + CO

36. A student prepared solutions of (i) an acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?

Solution

Student can use chemical indicator like phenolphthalein or natural indicators like turmeric, china rose etc.

37. How would you distinguish between baking powder and washing soda by heating?

Solution

CO₂ is released when we heat baking powder. This can be confirmed by passing evolved gas into lime water which will turn milky. CO₂ is not released when washing soda is heated.

38. Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B and C.

Solution

Baking powder (NaHCO₃), salt A is commonly used in bakery products. On heating it forms sodium carbonate (Na₂CO₃), B and CO₂ gas, C is evolved. When CO₂ gas is passed through lime water it forms calcium carbonate (CaCO₃), which is slightly soluble in water making it milky.

A — NaHCO₃

B — Na₂CO₃

C — CO₂ gas

39. In one of the industrial processes used for manufacture of sodium hydroxide, a gas X is formed as by product. The gas X reacts with lime water to give a compound Y which is used as a bleaching agent in chemical industry. Identify X and Y giving the chemical equation of the reactions involved. 

Solution

In the manufacture of sodium hydroxide, hydrogen gas and chlorine gas (X) are formed as by–products. Calcium oxychloride (bleaching powder) Y is formed when chlorine gas (X) reacts with lime water. The reactions are:
2NaCl (aq) + 2H₂O(l) → 2NaOH (aq) + Cl₂(g) + H₂(g)
X is Cl₂(Chlorine gas)
Ca (OH)₂(s) + Cl₂(g) → CaOCl₂(s) + H₂O
Y is Calcium oxychloride (bleaching powder)

40. Fill in the missing data in the following table  : 

		Salted Obtained from
Name of the Salt	Formula	Base	Acid
Ammonium chloride	NH4Cl	NH4OH	---
Copper sulphate	--	--	H2SO4
Sodium chloride	NaCl	NaOH	----
Magnesium nitrate	Mg(NO3)2	---	HNO3
Potassium sulphate	K2SO4	--	--
Calcium nitrate	Ca(NO3)2	Ca(OH)2	--

Solution

		Salted Obtained from
Name of the Salt	Formula	Base	Acid
Ammonium chloride	NH4Cl	NH4OH	HCl
Copper sulphate	CuSO4	Cu(OH)2	H2SO4
Sodium chloride	NaCl	NaOH	HCl
Magnesium nitrate	Mg(NO3)2	Mg(OH)2	HNO3
Potassium sulphate	K2SO4	KOH	H2SO4
Calcium nitrate	Ca(NO3)2	Ca(OH)2	HNO3

41. What are strong and weak acids? In the following list of acids, separate strong acids from weak acids. Hydrochloric acid, citric acid, acetic acid, nitric acid, formic acid, sulphuric acid.

Solution

Strong acids ionise completely in aqueous solutions and provide hydronium ions whereas weak acids are partially ionised and produce a much smaller concentration of H₃O⁺ ions.

• Strong acids —Hydrochloric acid, sulphuric acid, nitric acid
• Weak acid — Citric acid, acetic acid, formic acid

42. When zinc metal is treated with a dilute solution of a strong acid, a gas is evolved, which is utilised in the hydrogenation of oil. Name the gas evolved. Write the chemical equation of the reaction involved and also write a test to detect the gas formed. 

Solution

When zinc reacts with dilute solution of strong acid, it forms salt and hydrogen gas is evolved.

Zn + 2HCl → ZnCl₂+ H₂

The gas burns with a pop sound when a burning splinter is brought near the mouth of the test tube.

Long Answer Questions

43. In the following schematic diagram for the preparation of hydrogen gas as shown in Figure 2.3, what would happen if following changes are made? 

(a) In place of zinc granules, same amount of zinc dust is taken in the test tube
(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken
(c) In place of zinc, copper turnings are taken
(d) Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.

Solution

(a) Reaction speed increases if zinc dust is used in place of Zinc granules.

(b) If dilute hydrochloric acid is used instead of dilute sulphuric acid, zinc chloride will be formed.
Zn+ 2HCl→ ZnCl₂+H₂

(c) No reaction will take place if copper is used in place of zinc. This is because copper does not react with dilute acids.

(d) If we use NaOH solution in place of acid, sodium zincate is produced.
Zn+2NaOH→ Na₂ZnO₂+ H₂

44. For making cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake, 
(a) How will it affect the taste of the cake and why?
(b) How can baking soda be converted into baking powder?
(c) What is the role of tartaric acid added to baking soda?

Solution

(a) Baking soda is sodium hydrogen carbonate. On heating, it is converted into sodium carbonate which is bitter to taste.

2NaHCO₃  + Heat → Na₂Co₃ + CO₂ + H₂O  
(b) By the addition of appropriate amount of tartaric acid baking soda can be converted into baking powder.
(c) The role of tartaric acid is to neutralise sodium carbonate and cake will not taste bitter. 

45. A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z. 

Solution

Chlorine (G)gas is evolved at anode during electrolysis of brine. When chlorine gas is passed through dry Ca(OH)₂(Y) produces bleaching powder (Z) used for disinfecting drinking water.

Since Y and Z are calcium salts, therefore X is also a calcium salt and is calcium carbonate.

• CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O
• Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

46. A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by–product of chloralkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.

Solution

NaOH is the byproduct of the chloralkali process. Hence compound B is NaOH. Neutralization process occurs when NaOH is treated with acidic oxide. For example, if NaOH is treated with carbon dioxide, it gives sodium carbonate.

2NaOH + CO₂ → Na₂CO₃ + H₂O

47. A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance, which can be moulded into different shapes by making its dough. When this compound is left in open for some time, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.

Solution

Plaster of Paris is used for making different shapes. Its chemical name is calcium sulphate hemihydrate (CaSO₄.H₂O). Calcium sulphate hemihydrate is soft as the two formula unit of CaSO­₄ share one molecule of water. When it is left open for some time, it absorbs moisture from the atmosphere and forms gypsum, which is a hard solid mass.

48. Identify the compound X on the basis of the reactions given below. Also, write the name and chemical formulae of A, B and C.

Solution

1. 2NaOH+ Zn→ Na_₂ZnO_₂ + H₂(g)
2. NaOH + HCl →NaCl + H₂O
3. NaOH + CH₃COOH→ CH₃COONa + H₂O

X— NaOH (Sodium hydroxide)

A— Na₂ZnO₂(Sodium zincate)

B— NaCl (Sodium chloride)

C— CH₃COONa (Sodium acetate)