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

Question

NCERT Solution for Class 10 Science Chapter 2 Acids, Bases and Salts provides you with the understanding and in-depth analysis of Acids, Bases, and Salts. Acids, Bases, and Salts are one of the most interesting and important chapters of NCERT. This chapter is one of the most important chapters of chemistry. In this article, you can also get solutions for NCERT intext questions and solutions for exercise.

Our NCERT solutions are strictly based on the latest syllabus provided by the CBSE and it gives you a thorough and clear understanding of all the topics related to Acids, Bases, and Salts. In NCERT Solutions Class 10 Science Chapter 2 Acids, Bases and Salts you can learn about acids, bases, and salts and their different types, Chemical properties of Acid and Bases, Acid and bases tests, the reaction of acid and bases, and formation of salts and chemicals made from common salts, litmus tests, the importance of pH in everyday life, the water of crystallization, etc. An overall deep understanding of all the topics related to this chapter will help in your homework and assignments. According to the previous year's examination question paper, every year 3-4 questions are asked from this chapter for the class 10 examination. Being one of the easiest and most important chapters it is advised to practice and have a good command on this chapter to ace examination and score full marks. Our NCERT Solutions Class 10 Science  also have intext questions, it is nicely organized, very concise, have a practical-based question for better understanding.

Now all the NCERT solutions and practice questions are at your fingertip, get started now.

Answer 1

Chapter 2

Acids, Bases, and Salts

Class X

EXERCISE SOLUTIONS

Question 1:

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

(a) 1          

(b) 4                   

(c) 5                

(d) 10

Answer 1:

(d) Bases turn red litmus blue and acids turn blue litmus red. The basic solution has a pH value of more than 7. Since the solution turns red litmus blue, its pH is likely to be 10.

Question 2:

A solution reacts with crushed eggshells to give a gas that turns lime-water milky. The solution contains

(a) NaCl         

(b) HCl          

(c) LiCl         

(d) KCl

Answer 2:

(b) The solution contains HCl.

Question 3:

10 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) 8mL 

(c) 12 mL 

(d) 16 mL

Answer 3:

(d) 16 mL of HCl solution will be required.

Question 4:

Which one of the following types of medicines are used for treating indigestion?

(a) Antibiotic 

(b) Analgesic 

(c) Antacid 

(d) Antiseptic

Answer 4:

(c) Antacid is used for treating indigestion.

Question 5:

Write word equations and then balanced equations for the reaction taking place when −

(a) dilute sulphuric acid reacts with zinc granules.

(b) dilute hydrochloric acid reacts with magnesium ribbon.

(c) dilute sulphuric acid reacts with aluminum powder.

(d) dilute hydrochloric acid reacts with iron filings.

Answer 5:

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

      H₂SO₄(aq) + Zn(s) → ZnSO₄(aq) + H₂(g)

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

       2HCl(aq) + Mg(s) → MgCl₂(aq) + H₂(g)

(c) Sulphuric acid + Aluminium → Aluminium sulphate + Hydrogen

       3H2SO₄(aq) + 2Al(s) → Al₂(SO₄)₃(aq) + 3H₂(g)

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

      6HCl(aq) + 2Fe(s) → 2FeCl₃(aq) + 3H₂(g)

Question 6:

Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.

Answer 6:

Two nails are fitted on a cork and are kept in a 100 mL beaker. The nails are then connected to the two terminals of a 6-volt battery 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. Therefore, it does not conduct electricity.

Conclusion: From this activity, it can be concluded that all acids contain hydrogen but not all compounds containing hydrogen are acids. That is why, though alcohols and glucose contain hydrogen, they are not categorised as acids.

Question 7:

Why does distilled water not conduct electricity, whereas rainwater does?

Answer 7:

Distilled water is a pure form of water and is devoid of any ionic species. Therefore, it does not conduct electricity. Rainwater, being an impure form of water, contains many ionic species such as acids and therefore it conducts electricity.

Question 8:

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

Answer 8:

Acids do not show acidic behavior in the absence of water because the dissociation of hydrogen ions from an acid occurs in the presence of water only. It is the hydrogen ions that are responsible for the acidic behavior.

Question 9:

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

(a) neutral? 

(b) strongly alkaline? 

(c) strongly acidic? 

(d) weakly acidic? 

(e) weakly alkaline?

Arrange the pH in increasing order of hydrogen-ion concentration.

Answer 9:

(a) Neutral → Solution D with pH 7 

(b) Strongly alkaline → Solution C with pH 11 

(c) Strongly acidic → Solution B with pH 1 

(d) Weakly acidic → Solution A with pH 4 

(e) Weakly alkaline → Solution E with pH 9

The pH can be arranged in the increasing order of the concentration of hydrogen ions as: 11 < 9 < 7 < 4 < 1

Question 10:

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?

Answer 10:

The fizzing will occur strongly in test tube A, in which hydrochloric acid (HCl) is added. This is because HCl is a stronger acid than CH3COOH and therefore produces hydrogen gas at a faster speed due to which fizzing occurs.

Question 11:

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

Answer 11:

The pH of milk is 6. As it changes to curd, the pH will reduce because curd is acidic in nature. The acids present in it decrease the pH.

Question 12:

A 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 time to set as curd?

Answer 12:

(a) The milkman shifts the pH of the fresh milk from 6 to slightly alkaline because, in alkaline conditions, milk does not set as curd easily.

(b) Since this milk is slightly more basic than usual milk, acids produced to set the curd are neutralized by the base. Therefore, it takes a longer time for the curd to set.

Question 13:

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

Answer 13:

Plaster of Paris (POP) should be stored in a moisture-proof container because Plaster of Paris, a powdery mass, absorbs water (moisture) to form a hard solid known as gypsum.

Question 14:

What is a neutralization reaction? Give two examples.

Answer 14:

A reaction in which 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. 

For example: 

1. NaOH (Base) + HCl (Acid) → NaCl (Salt) + H₂O (Water)
2. During indigestion (caused due to the production of excess hydrochloric acid in the stomach), we administer an antacid (generally milk of magnesia, Mg(OH)₂ which is basic in nature). The antacid neutralizes the excess of acids and thus gives relief from indigestion. 

Mg(OH)₂ + 2HCl → MgCl₂ +2H₂O

Question 15:

Give two important uses of washing soda and baking soda.

Answer 15:

Two important uses of washing soda and baking soda are as follows:

(1) Washing soda:

(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:

(a) It is used as baking powder. Baking powder is a mixture of baking soda and a mild acid known as tartaric acid. When it is heated or mixed in water, it releases CO2 that makes bread or cake fluffy.

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

Answer 2

Page 18

Question 1:

You 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?

Answer 1:

If the colour of red litmus paper gets changed to blue, then it is a base and if there is no colour change, then it is either acidic or neutral. Thus, a basic solution can be easily identified.

Let us mark the three test tubes as A, B, and C. A drop of the solution in A is put on the red litmus paper. The same is repeated with solutions B and C. If either of them changes colour to blue, then it is basic. Therefore, out of three, one is eliminated. Out of the remaining two, anyone can be acidic or neutral. Now a drop of basic solution is mixed with a drop of each of the remaining two solutions separately and then the nature of the drops of the mixtures is checked. If the colour of red litmus turns blue, then the second solution is neutral and if there is no change in colour, then the second solution is acidic.

This is because acidic and basic solutions neutralize each other. Hence, we can distinguish between the three types of solutions.

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Page 22

Question 1:

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

Answer 1:

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, thereby spoiling the food.

Metal + Acid → Salt + Hydrogen gas

Zn(Metal) + 2H₂SO₄(Acid) → Zn(SO4)₂(Salt) + 2H₂(Hydrogen)

Question 2:

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

Answer 2:

Hydrogen gas is usually liberated when an acid reacts with a metal.

Take a few pieces of zinc granules and add 5 ml of dilute H2SO4. Shake it and pass the gas produced into a soap solution. The bubbles of the soap solution are formed. These soap bubbles contain hydrogen gas.

Zn (Zinc) + 2H₂SO₄ (Sulphuric Acid) → Zn(SO4)₂ (Sodium Hydroxide) + 2H₂ (Hydrogen)

We can test the evolved hydrogen gas by its burning with a pop sound when a candle is brought near the soap bubbles.

Question 3:

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 if one of the compounds formed is calcium chloride.

Answer 3:

CaCO₃ (Calcium Carbonate) + 2HCl (Hydrochloric Acid) → CaCl₂ (Calcium Chloride) + CO₂ (Carbon dioxide) + H₂O (Water)

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Page 25

Question 1:

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

Answer 1:

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

The reaction is as follows:

HCl + Water → H⁺ + Cl^-

H⁺ + H₂O → H3O⁺

Although aqueous solutions of glucose and alcohol contain hydrogen, these cannot dissociate in water to form hydrogen ions. Hence, they do not show acidic character

Question 2:

Why does an aqueous solution of acid conduct electricity?

Answer 2:

Acids dissociate in aqueous solutions to form ions. These ions are responsible for conduction of electricity.

Question 3:

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

Answer 3:

Colour of the litmus paper is changed by the hydrogen ions. Dry HCl gas does not contain H+ ions. It is only in the aqueous solution that an acid dissociates to give ions. Since in this case, neither HCl is in the aqueous form nor the litmus paper is wet, therefore, the colour of the litmus paper does not change.

Question 4:

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

Answer 4:

The process of dissolving an acid or a base in water is a highly exothermic one. Care must be taken while mixing concentrated nitric acid or sulphuric acid with water. The acid must always be added slowly to water with constant stirring. If water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.

Question 5:

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

Answer 5:

When an acid is diluted, the concentration of hydronium ions (H₃O⁺ ) per unit volume decreases. This means that the strength of the acid decreases.

Question 6:

How is the concentration of hydroxide ions (OH^– ) affected when excess base is dissolved in a solution of sodium hydroxide?

Answer 6:

The concentration of hydroxide ions (OH⁻) would increase when the excess base is dissolved in a solution of sodium hydroxide.

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Page 28

Question 1:

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

Answer 1:

A pH value of less than 7 indicates an acidic solution, while greater than 7 indicates a basic solution. Therefore, the solution with pH = 6 is acidic and has more hydrogen ion concentration than the solution of pH = 8 which is basic.

Question 2:

What effect does the concentration of H⁺ (aq) ions have on the nature of the solution?

Answer 2:

The concentration of H⁺ (aq) can have a varied effect on the nature of the solution. With an increase in H+ ion concentration, the solution becomes more acidic, while a decrease in H⁺ ion causes an increase in the basicity of the solution.

Question 3:

Do basic solutions also have H⁺ (aq) ions? If yes, then why are these basic?

Answer 3:

Yes, the basic solution also has H⁺ (aq) ions. However, their concentration is less as compared to the concentration of OH⁻ ions which makes the solution basic.