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

NCERT Solutions for Class 10 Science Chapter 2: The NCERT Solutions for Class 10 Science Chapter 2 offer detailed explanations for each question in the textbook, ensuring clarity in fundamental concepts. They present answers in a step-by-step format, which helps students tackle theoretical as well as numerical problems efficiently.

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NCERT Solutions for Class 10 Science Chapter 2 PDF

NCERT Solutions for Class 10 Science Chapter 2 PDF

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

1. You are given three test tubes. The three test tubes contain distilled water, an acidic solution and the basic solution, respectively. There is only red litmus paper available in order to identify what is there in each test tube. How will you find out what is in each of the test tubes?

Solution:

• The three solutions in the test tubes are poured one at a time onto litmus paper.
• A basic answer can be found in the solution that changes red litmus to blue.
• The blue litmus paper should be divided into two sections.
• The acidic solution is the one in the test tube that causes the blue litmus paper to become red.
• Water is included in the test tube solution, which does not alter the colour of the red or blue litmus paper.

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In-text questions set 2 — Page number 22

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

Solution:

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?

Solution: When an acid reacts with any metal, salt and hydrogen gas are formed.

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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.

Solution:

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In-text questions set 3 Page number – 25

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

Solution:

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

Solution:

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

Solution: HCl does not give out Hydrogen ions; therefore, HCl does not show any acidic behaviour, and the colour of the litmus paper remains the same on reacting with HCl gas.

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

Solution:

5. How is the concentration of hydronium ions (H ₃ O ⁺ ) affected when a solution of an acid is diluted?

Solution:

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

Solution:

In-text questions set 4 Page number – 33

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?

Solution:

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

Solution:

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

Solution: Basic solutions have H ⁺ ions, but hydroxide ions present in basic solution are more in basic solution. Hence, Hydroxide ions turn the solution into basic.

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

Solution:

In-text questions set 5 Page number – 34-35

1. What is the common name of the compound CaOCl ₂ ?

Solution: The common name of CaOCl ₂ is bleaching powder.

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

Solution: The substance, which on treatment with chlorine, yields bleaching powder is Calcium hydroxide.

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

Solution: Sodium carbonate is the compound which is used for softening hard water.

4. What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.

Solution: Heating sodium hydrocarbonate yields sodium carbonate, and carbon dioxide gas is liberated in the process.

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

Solution: The chemical equation for the reaction of Plaster of Paris and water is

Exercise questions Page number – 33

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

a) 1 (b) 4 (c) 5 (d) 10

Solution: The answer is 10 because litmus paper turns blue when the solution reacts with a basic solution (PH more than 7). Hence, 10 is the answer.

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

Solution: The answer is HCl.

3. 10 mL of a solution of NaOH is found to be completely neutralised 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 neutralise it will be

(a) 4 mL (b) 8 mL (c) 12 mL (d) 16 mL

Solution: Since 10 ml of NaOH requires 8 mL of HCL, 20 ml of NaOH requires 8 x 2 = 16mL of HCl. Hence, the answer is option (d) 16mL.

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

(a) Antibiotic (b) Analgesic (c) Antacid (d) Antiseptic

Solution: Indigestion is due to the excess production of acid in the stomach. Medicines used to treat indigestion is called Antacid.

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 aluminium powder.

(d) Dilute hydrochloric acid reacts with iron filings.

Solution:

=> Dilute sulphuric acid + zinc → Zinc Sulphate + Hydrogen Gas

=> H ₂ SO ₄ (aq) + Zn → ZnSO ₄ (aq) + H ₂ (g)

=> Dilute Hydrochloric + Magnesium → Magnesium Chloride + Hydrogen Gas

=> 2HCl(aq) + Mg → MgCl ₂ (aq) + H ₂ (g)

=> Dilute Sulphuric Acid + Aluminium → Aluminium Sulphate + Hydrogen Gas

=> 3H ₂ SO ₄ (aq) + 2Al(s) → Al ₂ (SO ₄ ) ₃ (aq) + 3H ₂ (g)

=> Dilute Hydrochloric Acid + Iron → Ferrous Chloride + Hydrogen Gas

=> 6HCl(aq) + 3Fe(s) → 3FeCl ₂ (aq) + 3H ₂ (g)

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

Solution:

7. Why does distilled water not conduct electricity, whereas rain water does?

Solution:

• There are no ionic compounds found in distilled water.
• Rainwater, on the other hand, contains far more chemicals.
• Carbonic acid is created when acidic gas, such as carbon dioxide from the atmosphere, dissolves in rainwater. This indicates that it contains carbonate and hydrogen ions. Rainwater can therefore conduct electricity when it contains acids.

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

Solution:

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?

(c) Strongly acidic?

(d) Weakly acidic?

(e) Weakly alkaline?

Solution: In increasing order of hydrogen ion concentration,

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 (CH ₃ COOH) is added to test tube B. Amount and concentration taken for both the acids are the same. In which test tube will the fizzing occur more vigorously and why?

Solution:

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

Solution: Fresh milk is turned to curd due to the production of lactic acid. Lactic acid reduces the pH of the milk.

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?

Solution: (a) He shifted the pH of the fresh milk from 6 to slightly alkaline to prevent milk from getting sour due to the production of lactic acid.

(b) This milk takes a long time to set into curd because the lactic acid produced here first neutralises the pH, and then the pH is reduced to turn the milk into curd.

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

Solution:

14. What is a neutralisation reaction? Give two examples.

Solution: The reaction of the acid + base gives a product of salt + water, which is considered a neutralisation reaction.

15. Give two important uses of washing soda and baking soda.

Solution:

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