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

Solutions of Chapter 2 Acids, Bases, and Salts of NCERT Science for Class 10 contains all the main and important topics which have a complete and detailed description. Solutions of Chapter 2 Acids, Bases, and Salts of NCERT Science for Class 10 will help the students of class 10 to understand concepts. Class 10 Science Chapter 2 Question Answer in Hindi will be very helpful for Hindi medium students.

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

You must know the topics and subtopic of Chapter 2 Acids, Bases, and Salts of NCERT Science for Class 10 before you go through the Solutions of Chapter 2 Acids, Bases and Salts of NCERT Science for Class 10.

. Understanding The Chemical Properties of Acids and Bases
. What Do All Acids and All Bases Have In Common?
. How Strong Are Acids or Bases Solutions?
. More About Salts

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Solutions of Chapter 2 Acids, Bases, and Salts of NCERT Science for Class 10 Intext questions

Chapter-2- Acids, Bases, and salts

TEXTBOOK QUESTIONS:

Questions (Page 18)

Q.1You have been provided with three test tubes. One of them contains distilled water and the other two contain 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?

Ans. At first, we will dip the red litmus paper in all the test tubes, the test tube in which red litmus changes to blue, contains a basic solution. Now dip the so-changed blue litmus paper in the other two test tubes, the test tube in which blue litmus changes to red in acidic solution, and the third test tube will contain distilled water.

Questions (Page 22)

Q. 1 Why should curd and sour substances not be kept in brass and copper vessels?

Ans. Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products and food items get spoiled, that’s why it is advised not to store curds and other sour substances in the brass or copper vessels.

Q.2 Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test the presence of the gas?

Ans. When an acid reacts with a metal, Hydrogen gas is liberated

We take a few pieces of zinc granules and add 5 ml of dilute H₂SO₄. After some time gas is produced which is passed into a soap solution. The bubbles of the soap solution are formed. These soap bubbles contain hydrogen gas. When we take a burning candle near bubbles, they burst with pop sound which proves that evolving gas is Hydrogen.

2H₂SO₄+Zn → Zn(SO₄)₂+ 2H₂↑

Q.3 A metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction when one of the compounds formed is calcium chloride.

Ans. Metal compound ‘A’ reacts with dilute hydrochloric acid to form a gas which extinguishes the burning candle means produced gas is carbon dioxide. Another product is calcium chloride, so compound A is a carbonate of calcium.

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Questions (Page 25)

Q.1 Why do HCl, HNO₃ etc. show acidic character in aqueous solutions while solutions of compounds like C₂H₅OH and glucose do not show acidic character?

Ans.HCl, and HNO₃ show acidic character in aqueous solutions, because they produce H⁺ (aq) ions, although aqueous solutions of glucose and alcohol contain hydrogen but these cannot dissociate in water to form hydrogen ions. Hence, they do not show an acidic character.

The dissociation of HCl or HNO₃ to form hydrogen ions always occur in the presence of water. Hydrogen ions (H+) combine with H₂O to form hydronium ions (H₃O⁺)

HCl_(aq)→ H⁺+ Cl^-

H⁺+ H₂O → H₃O+

Q.2 Why does an aqueous solution of acid conduct electricity?

Ans. An aqueous solution of an acid conducts electricity because in aqueous solution acid produces cations and anions. These ions are responsible for the conduction of electricity.

Q.3 Why does dry HCl gas not change the colour of dry litmus paper?

Ans.H⁺ ions are responsible for the acidic character of HCl, and the change of litmus paper. H+ ions are formed in the presence of water only. So dry HCl does not produce H ⁺ with dry litmus paper, that’s why dry HCl gas cannot change the colour of dry litmus paper.

Q.4 While diluting the acid why is it recommended that acid should be added to water and not the water to the acid?

Ans. The process of dissolving an acid in water is the exothermic reaction when a small amount of water is added to an acid, due to this heat is produced and the vapour of water evolve and acid with water vapour spill and may cause injury so it is always recommended that acid should be added to water.

Q.5 How is the concentration of hydronium ions (H₃O⁺) affected when a solution of an acid is diluted?

Ans. When a solution of an acid is diluted, the concentration of hydronium ions (H₃O+) is decreased.

Q. 6 How is the concentration of hydroxide ions (OH-) affected when an excess base is dissolved in a solution of sodium hydroxide?

Ans. When the excess base is dissolved in a solution hydroxide, the concentration of hydroxide (OH-) ions would increase.

Questions (Page 28)

Q. 1 You have two solutions A and B. pH of solution A is 6 and the pH of the solution, B is 8. Which solution has more hydrogen ion concentration? Which of these is acidic and which one is basic?

Ans. A pH value of less than 7 indicates an acidic solution, while greater than 7 indicates a basic solution.

So, the solution with pH = 6 is acidic and the solution of pH = 8 is basic. So solution A with P^H-6 has more hydrogen ions than solution B.

Q. 2 What effect does the concentration of H⁺ (aq) have on the acidic nature of the solution?

Ans. The concentration of H⁺ (aq) is directly proportional to the acidic nature of the solution. More concentration of H⁺ (aq) ions, means more acidic nature and less concentration of H⁺ (aq) ions mean the less acidic nature of a solution.

Q.3 Do basic solutions also have H⁺ (aq) ions? If yes, then why are they basic?

Ans. Yes, the basic solution also has H⁺ ions. But their concentration is less as compared to the concentration of OH^-ions, that’s why they are basic in nature.

Q.4 Under what soil conditions do you think a farmer would spread or treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate).

Ans. If the soil is acidic and improper for cultivation, then to increase the basicity of the soil, the farmer would treat the soil with quick lime or slaked lime or chalk because Quick lime, slaked lime, and chalk are basic in nature

Questions (Page 33)

Q. 1 What is the common name of the compound CaOCl₂?

Ans.Bleaching powder.

Q.2 Name the substance which on treatment with chlorine, yields bleaching powder?

Ans.Dry slaked lime [Calcium hydroxide (Ca (OH)₂]

Q.3Name sodium compound which is used for softening of hard water.

Ans. Washing soda [sodium carbonate(Na ₂CO₃.10H₂O)] is used for softening hard water.

Q.4 What will happen if the solution of sodium hydrogen carbonate is heated?

Ans.On heating sodium hydrogen carbonate changes to sodium carbonate.

2NaHCO₃ → Na₂CO₃+H₂O + CO₂↑

Q.5 Write an equation to show the reaction between the plaster of Paris and water.

CaSO₄ . H₂O + H₂O → CaSO₄ . 2H₂O

(Plaster of Paris) ( Gypsum)

EXERCISES:

Q.1A solution turns red litmus blue, its pH is likely to be

(a) 1 (b) 4

Ans. (d) 10

Q.2 A solution reacts with crushed eggshells to give a gas that turns lime-water milky, the solution contains.

(a) NaCl (b) HCl

Ans. (d) HCl

Q.310 mL of a solution of NaOH is found to be completely neutralized by 8 mL of a given solution of HCl. If we take 20 ml of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralize it will be

(a) 4 mL (b) 8 mL

Ans. (d) 16 mL

Q.4 Which one of the following types of medicines is used for treating indigestion?

(a) Antibiotic (b) Analgasic

Ans. (d) Antacid

Q.5 Write the word equation and then balanced equation when -

(a) Dilute sulphuric acid reacts with zinc granules

(b) Dilute hydrochloric acid reacts with magnesium ribbon

(d) Dilute hydrochloric acid reacts with iron filings

Ans.

(a) Sulphuric acid + Zinc → Zinc sulphate + Hydrogen

H₂SO_4(aq) + Zn_(s) → ZnSO_4(aq + H_2(g)

(b) Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen

2HCl_(aq)+ Mg_(s) → MgCl_2(aq)+ H_2(g)

3H₂SO_{4(aq) +} 2Al_(s) → Al₂(SO₄)_3(aq)+ 3H_2(g)

(d) Hydrochloric acid + Iron → Ferric chloride + Hydrogen

6HCl_(aq) + 2Fe_9s) → 2FeCl_3(aq) + 3H_2(g)

Q.6 Compounds like alcohol and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.

Ans.Object- The hydrogen ion present in acids is ionic while the hydrogen ion in alcohol, and glucose is not ionic

Method- At first we prepare aqueous solutions of alcohol, glucose, hydrochloric acid. Now we take a 100ml capacity beaker and two nails are fitted on a cork and in it. The nails are then connected to the two terminals of a 6-volt battery, ammeter, a torch bulb, and switch through a bulb and a switch. Some dilute HCl is poured into the beaker and the current is switched on. The same experiment is then performed with glucose solution and alcohol solution.

Observations:

It will be observed that the bulb glows in the HCl solution and does not glow in the glucose solution.

Result:

HCl dissociates into H⁺and Cl^-ions. These ions conduct electricity in the solution resulting in the glowing of the bulb. On the other hand, the glucose solution does not dissociate into ions. So, it does not conduct electricity.

Q. 7 Why does distilled water not conduct electricity whereas rainwater does?

Ans. Distilled water is a pure form of water and it does not have any ionic species. Therefore, it does not conduct but on the other hand, rainwater dissolves atmospheric carbon dioxide to form carbonic acid (H₂CO₃) which forms H⁺ ions due to the presence of H⁺ ions, rain water conducts electricity, but distilled water cannot.

Q.8 Why do acids not show acidic behavior in the absence of water?

Ans. Acids produce Hydrogen ions in water only and these ions are not produced in dry acids. Hydrogen ions are responsible for an acidic character so acids do not show acidic behavour in the absence of water.

Q.9 Five solutions A, B, C, D, and E when tested with a universal indicator showed pH as 4, 1, 11, 7, and 9 respectively. Which solution is:

(a) neutral?

(b) Strongly alkaline?

(d) Weakly acidic?

(e) Weakly alkaline?

Arrange the pH in increasing order of hydrogen ion concentration.

Ans.

Solutions	Showing P^H
Neutral	7 (solution –D)
Strongly alkaline	11(solution- C)
Strongly acidic	1(solution – B)
Weakly acidic	4 (solution – A)
Weakly alkaline	9 (solution – E)

pH in increasing order of hydrogen ion concentration 11 < 9 < 7 < 4 < 1.

Q.11 Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A while acetic acid (CH₃COOH) is added to test tube B. In which test tube will the fizzing occur more vigorously and why?

Ans. The fizzing will occur more vigorously in test tube A because HCl is a strong acid and it produces more number of H⁺ ions whereas acetic acid is a weak acid.

Q.12 Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Ans. When milk changes to curd it pH will decrease below the value of 6 due to the formation of lactic acid.

Q.13A Milkman adds a very small amount of baking soda to fresh milk.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a long to set as curd?

Ans.

(a) The milkman shifts the pH of the fresh milk from 6 to slightly alkaline by

adding a small amount of baking soda, because in alkaline conditions, milk does not set as curd easily.

so that it may take time to lower the pH of lactic acid.

(b)By the action of microorganisms, lactic acid is formed which has a pH of about 3, but

When baking soda is added to this, the pH of the milk goes above 7, due to this acid in the milk is neutralized by the base. Therefore, it takes a longer time for the curd to set.

Q.1 Plaster of Paris should be stored in a moisture-proof container. Explain why?

Ans. The plaster of Paris changes to a hard substance reacting with water. That’s why; it is stored in a moisture-proof container.

. CaSO₄ . H₂O+ H₂O → CaSO₄. 2H₂O

(Plaster of Paris) ( Gypsum- Hard solid substance)

Q. 15 What is a neutralization reaction? Give two examples.

Ans. When an acid and base react with each other to give salt and water is termed a neutralization reaction. In this reaction, energy is evolved in the form of heat.

NaOH + HCl→ NaCl+ H₂O

Q.16 Give two important uses of washing soda and baking soda.

Ans. 1) Washing soda (Na₂CO₃.10H₂O)

(a) It is used in glass, soap, and paper industries.

(b) It is used to remove the permanent hardness of the water.

(2) Baking soda(_NaHCO₃)

(a) It is used as baking powder. Baking powder is a mixture of baking soda and a mild acid known as tartaric acid.

(b) It is used in soda-acid fire extinguishers

These NCERT solutions and study materials will help you good marks for your CBSE Board and Other state board exams.

NCERT Solutions for Class 10 Science All Chapters below

Chapter 1 Chemical Reactions and Equations

Chapter 2 Acids, Bases, and Salts