What are acids and bases?

Acids are substances that release H⁺ ions in water, while bases release OH⁻ ions. They show distinct properties and reactions.

What are indicators in acids and bases?

Indicators are substances that change color in acidic or basic solutions, e.g., litmus, phenolphthalein, methyl orange.

Are these notes useful for competitive exams?

Yes, these notes help students prepare for NEET, SSC, Railway, Police Bharti exams as well as Class 10 board exams.

Anacidis a substance that producesH+ions in aqueous solution. They taste sour and turn blue litmus red.

2. What is a base (alkali)?

Abaseis a substance that producesOH-ions in aqueous solution. Soluble bases are calledalkalis; they taste bitter and turn red litmus blue.

Asaltis an ionic compound formed when the H+of an acid is replaced by a metal or ammonium ion. Example: NaCl from HCl + NaOH.

4. What is neutralisation?

Neutralisationis a reaction between an acid and a base to form salt and water. Example: HCl + NaOH → NaCl + H2O.

5. What are indicators?

Indicatorsare substances that change colour to show whether a solution is acidic or basic. Examples: litmus, phenolphthalein, methyl orange.

6. What happens when an acid reacts with a metal?

An acid reacts with many metals to produce asaltandhydrogen gas. Example: Zn + 2HCl → ZnCl2+ H2↑.

7. What happens when an acid reacts with a carbonate or hydrogen carbonate?

Acids react with carbonates/hydrogen carbonates to give salt, CO2gas and water. Example: CaCO3+ 2HCl → CaCl2+ CO2↑ + H2O.

9. What is the pH scale?

pHis a measure of acidity/basicity. It ranges from 0-14: pH 7 basic. Lower pH means higher acidity.

10. What is a universal indicator?

Auniversal indicatoris a mixture of indicators that shows a range of colours for different pH values, allowing approximate pH determination.

11. Difference between strong and weak acids?

Strong acids(e.g., HCl, HNO3, H2SO4) ionise completely in water.Weak acids(e.g., CH3COOH) ionise partially.

12. Difference between strong and weak bases?

Strong bases(e.g., NaOH, KOH) dissociate completely in water;weak bases(e.g., NH3) accept protons partially or produce fewer OH-ions.

13. What do concentrated and dilute acids mean?

Concentratedacids have a large amount of acid per unit volume (less water);diluteacids have more water and less acid per unit volume. Concentration is different from strength.

15. Reaction between hydrochloric acid and magnesium?

Mg + 2HCl → MgCl2+ H2↑ (magnesium reacts vigorously producing hydrogen gas).

16. Reaction of an acid with metal oxide?

Acid + metal oxide → salt + water. Example: HCl + CuO → CuCl2+ H2O.

17. Reaction of acid with metal hydroxide (alkali)?

Acid + base → salt + water. Example: HCl + NaOH → NaCl + H2O (neutralisation).

18. How does phenolphthalein act as an indicator?

Phenolphthalein is colourless in acidic and neutral solutions and turns pink in basic solutions (pH > ~8.2).

19. How does methyl orange act as an indicator?

Methyl orange turns red in acidic solutions (pH ~4.4); useful in titrations.

21. What is baking soda and one of its uses?

Baking soda is sodium hydrogen carbonate (NaHCO3). Uses: in baking as a leavening agent, and to neutralise acids (e.g., antacid).

22. What is washing soda and one of its uses?

Washing soda is sodium carbonate decahydrate (Na2CO3·10H2O). Uses: in laundry detergents to soften water and remove grease.

23. What is bleaching powder and a common use?

Bleaching powder is calcium oxychloride, CaOCl2. Uses: disinfection of drinking water and bleaching of clothes.

Class 10 Science — Chapter 2: Acids, Bases & Salts

By RAAM SETU | NEET, SSC, Railway & Police Bharti Focused Notes 📘

📘 Introduction

This chapter explains Acids, Bases & Salts including properties, reactions, indicators, neutralization and examples. Vital for NEET, SSC, Railway, Police Bharti exams and Class 10 board exams.

🔹 Key Concepts

Acids: Substances releasing H⁺ ions in water
Bases: Substances releasing OH⁻ ions in water
Indicators: Litmus, phenolphthalein, methyl orange
Neutralization Reaction: Acid + Base → Salt + Water
pH Scale: Measures acidity or basicity of a solution

📊 Chapter Summary Table

Concept	Example / Formula	Use
Acid	HCl, H₂SO₄	Shows sour taste, reacts with metals
Base	NaOH, Ca(OH)₂	Shows bitter taste, reacts with acids
Neutralization	HCl + NaOH → NaCl + H₂O	Used to prepare salts & control pH

🧮 Practice Questions

Define acids and bases with examples.
Explain the working of indicators like litmus, phenolphthalein.
Write the reaction of HCl with NaOH.
Classify reactions as acid-base or neutralization.
Explain the pH scale and its significance.

Acids, Bases & Salts — 50 Q&A

NCERT Class 10 — Chapter 2. Tap to expand answers. Use the toggle to switch Light / Dark.

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NCERT Class 10 — Chapter 2: Acids, Bases & Salts

📘 Introduction

🔹 Key Concepts

📊 Chapter Summary Table

🧮 Practice Questions

1. What is an acid?

2. What is a base (alkali)?

3. What is a salt?

4. What is neutralisation?

5. What are indicators?

6. What happens when an acid reacts with a metal?

7. What happens when an acid reacts with a carbonate or hydrogen carbonate?

8. Give examples of acid reacting with a base (neutralisation) in everyday life.

9. What is the pH scale?

10. What is a universal indicator?

11. Difference between strong and weak acids?

12. Difference between strong and weak bases?

13. What do concentrated and dilute acids mean?

14. Write the reaction when sodium carbonate reacts with hydrochloric acid.

15. Reaction between hydrochloric acid and magnesium?

16. Reaction of an acid with metal oxide?

17. Reaction of acid with metal hydroxide (alkali)?

18. How does phenolphthalein act as an indicator?

19. How does methyl orange act as an indicator?

20. Describe the litmus test for acids and bases.

21. What is baking soda and one of its uses?

22. What is washing soda and one of its uses?

23. What is bleaching powder and a common use?

24. What is Plaster of Paris (POP) and a use?

25. How is baking soda (NaHCO3) prepared from sodium carbonate?

26. Outline how washing soda (Na2CO3) is industrially obtained starting from NaCl (brief).

27. How is common salt (NaCl) obtained and one major use?

28. Typical pH of human blood and its importance?

29. What is acid rain and its causes?

30. How do you test for carbon dioxide gas in the laboratory?

31. Briefly how is sodium chloride obtained from sea water?

32. One industrial use of NaOH (caustic soda)?

33. What happens when Plaster of Paris (POP) is mixed with water?

34. How do acids affect teeth?

35. Role of acid in digestion (stomach acid)?

36. What is a neutral salt? Give example.

37. What is an acidic salt? Example.

38. What is a basic salt? Example.

39. What is titration (brief) and its purpose?

40. Difference between end point and equivalence point?

41. Difference between antiseptic and disinfectant (brief)?

42. Important lab safety rules while handling acids and bases?

43. How do acids corrode metals? (link to acid rain)

44. What are amphoteric substances? Give an example.

45. Reaction between ammonia gas and hydrogen chloride gas?

46. How does soil pH affect plant growth and how are acids involved?

47. How do you choose an indicator for titration?

48. Give a common laboratory method to prepare CO2 gas.

49. List common mistakes students make in this chapter and tips to avoid them.

50. Quick revision points for exams (Chapter summary)?

25. How is baking soda (NaHCO₃) prepared from sodium carbonate?

26. Outline how washing soda (Na₂CO₃) is industrially obtained starting from NaCl (brief).

48. Give a common laboratory method to prepare CO₂ gas.