NCERT Solutions for Chapter 2 Acids, Bases and Salts Class 10 Science (original) (raw)

Last Updated : 23 Jul, 2025

**NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts- This article includes free NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts, developed by the top Biology experts at GFG, according to the latest **CBSE Syllabus 2023-24 and guidelines. The solutions to all the exercises in NCERT Class 10 Science Chapter 2 Acids, Bases and Salts have been collectively covered in NCERT Solutions for Class 10.

If you want to learn the basic concepts of NCERT Class 10 Science Chapter 2 Acids, Bases and Salts from scratch, refer to NCERT Class 10 Science Chapter 2 Acids, Bases and Salts.

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

Q1. A solution turns red litmus blue, its pH is likely to be

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

We know that a base turns red litmus blue. So the solution is most likely to be a base. Also bases have a pH value more than 7.

Thus option (d) 10 is the correct answer as no other option has a pH greater than 7.

Q2. A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains

(a) NaCl (b) HCl (c) LiCl (d) KCl

As the gas turns limewater milky, it is surely Carbon dioxide (CO2). We know that egg shells are made up of calcium carbonate. Thus carbon dioxide can be only released if calcium carbonate which is salt reacts with an acid.

CaCO3 + HCl → CaCl2 + H2O + CO2

Thus option (b) HCl is the correct answer as it is the only acid given in the options.

Q3. 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 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

HCl required to neutralize 10 ml of NaOH = 8 ml

HCl required to neutralize 1 ml of NaOH = 0.8 ml

HCl required to neutralize 20 ml of NaOH = 0.8 * 20 = 16 ml

Thus option (d) 16 ml is the correct answer.

Q4. Which one of the following types of medicines is used for treating indigestion?

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

We know that acidity is caused by excess acid in the stomach. So we need to neutralize the acid to cure indigestion. A substance that neutralizes an acid is a base. Thus we make use of an antacid which is a mild base.

Thus option (c) antacid is the correct answer.

Q5. **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.**

The reactions are as follows:

(a) H2SO4 (aq.) + Zn → ZnSO4 + H2 (g)

(b) HCl (aq) + Mg → MgCl2 + H2 (g)

(c) H2SO4 + Al → Al2(SO4)3 + H2 (g)

(d) HCl (aq.) + Fe → FeCl2 + H2

Q6. Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an activity to prove it.

**Objective: To prove that alcohols and glucose also contain hydrogen but are not categorized as acids

**Requirements: Two iron nails, wooden or rubber cork, beaker, bulb, battery, Wires, Alcohol or glucose, switch, HCl

**Procedure:

**Observations: We know that acids conduct electricity. Thus bulb glows when HCl is used which is an acid whereas it does not glow when alcohol or glucose were used.

**Result: Alcohols and glucose also contain hydrogen but are not categorized as acids

Q7. Why does distilled water not conduct electricity, whereas rain water does?

Rain water has certain gases dissolved in it such as nitrogen dioxide, sulphur dioxide and carbon dioxide from air. These gases form their acids such as carbonic acid, nitric acid and sulphuric acid when dissolved in rainwater which are ionic in nature. Thus rainwater has presence of ions in it which is responsible to conduct electricity. On the other hand, distilled water has no compounds dissolved in it and has no free ions to conduct electricity.

Q8. Why do acids not show acidic behavior in the absence of water?

The acidic behavior of acids is due to the presence of free hydrogen ions. In the absence of water, the acids do not dissociate into their respective ions and there are no free hydrogen ions. Thus no acidic behavior is seen in the absence of free hydrogen ions.

Q9. 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

(a) A neutral solution always has a pH value of 7. Thus D is a neutral solution.

(b) A strongly alkaline solution will have a pH value much closer to 14. Thus C is a strongly alkaline solution.

(c) A strongly acidic solution will have a pH value much closer to 1. Thus B is a strongly acidic solution.

(d) A weak acid has a pH value in between 1 and 7. Thus A is a weak acid.

(e) A weak alkaline solution has a pH value in between 7 and 14. Thus E is weakly alkaline.

Q10. 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. Amount and concentration taken for both the acids are the same. In which test tube will the fizzing occur more vigorously and why?

HCl is a strong acid and produces a good amount of hydrogen when it reacts with magnesium whereas acetic acid is a weak acid and less hydrogen is produced. Fizzing is the result of hydrogen formation. Thus test tube A will show fizzing vigorously due to presence of higher amount of hydrogen.

Q11. Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Fresh milk has a very small amount of lactic acid and thus it has a pH of 6. When milk turns into curd, the amount of lactic acid increases. As acids have a lower pH value, the pH of milk will become less than 6 when it turns into curd.

Q12. 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?

(a) The milk may get sour and thus get spoilt due to the production of lactic acid in the milk. Thus he shifts the pH of milk to slightly alkaline to prevent it from getting sour and spoilt.

(b) The milk takes longer to set as curd because a certain amount of lactic acid produced during curd formation is neutralized first by the baking soda present in milk which is a base. Thus the effect of that amount of lactic acid becomes zero and it milk takes longer to set as curd.

Q13. Plaster of Paris should be stored in a moisture-proof container. Explain why?

Plaster of Paris absorbs moisture to form calcium sulphate dihydrate which is called gypsum. This makes the Plaster of Paris useless for any purpose. Thus it is stored in a moisture-proof container.

CaSO4.1/2H2O (Plaster of Paris) + H2O (water) → CaSO4.2H2O (gypsum)

Q14. What is a neutralization reaction? Give two examples.

The reaction of an acid with a base to produce a salt and water is called neutralization reaction. Some examples of neutralization reaction are:

HCl + NaOH → NaCl + H2O

H2SO4 + Ca(OH)2 → CaSO4 + H2O

Q15. Give two important uses of washing soda and baking soda.

Two uses of washing soda are:

Two uses of baking soda are:

Important Topics Discussed in NCERT Class 10 Science Chapter 2 Acid, Bases and Salts

NCERT Class 10 Science Chapter 2 Acids, Bases and Salts covers the following topics:

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

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