🧪 CBSE · Class 10 · Science · Chapter 2

Acids, Bases
and Salts

Complete chapter resources for CBSE Class 10 Science — topic breakdown, key reactions and concepts, sample questions, previous year board questions, and instant AI question paper generation.

4Topics
5–7Board marks
8Sample questions
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Key Concepts & Reactions — Chapter 2
  • Neutralisation: Acid + Base → Salt + Water
  • Acid + Metal: Acid + Metal → Salt + H₂↑
  • Acid + Carbonate: Acid + Metal CO₃ → Salt + CO₂ + H₂O
  • pH scale: 0–6 acidic · 7 neutral · 8–14 basic
  • Washing soda: Na₂CO₃·10H₂O
  • Baking soda: NaHCO₃
Chapter Overview

What this chapter covers

Chapter 2 of CBSE Class 10 Science introduces the chemical properties of acids and bases at a deeper level than Class 7. Students learn how acids and bases react with metals, metal oxides, metal carbonates, and metal bicarbonates, and why these reactions produce characteristic products like hydrogen gas, carbon dioxide, and salts. The chapter uses everyday substances — vinegar, lemon juice, baking soda, caustic soda — to anchor the concepts in real life.

A central concept is the pH scale (0–14), introduced to measure the concentration of H⁺ ions in solution. A pH below 7 indicates an acidic solution, exactly 7 is neutral, and above 7 is basic. Students explore how universal indicator and natural indicators (turmeric, litmus, China rose) change colour with pH, and study the biological importance of pH — in digestion, tooth decay, soil quality, and acid rain.

The chapter concludes with an in-depth study of salts — their families, the pH of salt solutions, and the preparation and uses of important salts such as sodium chloride, washing soda (Na₂CO₃·10H₂O), baking soda (NaHCO₃), bleaching powder (CaOCl₂), and plaster of Paris (CaSO₄·½H₂O). Board questions consistently test balanced chemical equations, the preparation of these salts, and their practical applications.

Topics

What's inside Chapter 2

As per NCERT Class 10 Science (CBSE syllabus)

Topic 1
Chemical Properties of Acids and Bases
Reactions of acids and bases with metals, metal oxides, metal carbonates, metal bicarbonates, and with each other (neutralisation). Recognising patterns in products formed.
Topic 2
What Do All Acids and Bases Have in Common?
Behaviour in aqueous solutions — acids produce H⁺ (H₃O⁺) ions and bases produce OH⁻ ions. Concepts of dilution, strength of acids and bases, and the role of water in ionisation.
Topic 3
pH Scale and Importance of pH
The pH scale (0–14), universal indicator, natural indicators. Biological significance: pH of digestive system, tooth decay, soil pH, acid rain, and self-defence by animals and plants.
Topic 4
Salts — Families, Preparation, and Uses
pH of salt solutions, common salt (NaCl) and its products (NaOH, Na₂CO₃, NaHCO₃), bleaching powder, washing soda, baking soda, and plaster of Paris — preparation, properties, and uses.
Connections

How this chapter fits in

Useful for setting question difficulty and cross-chapter papers.

Builds on
Class 7 · Acids, Bases & Salts
Litmus test, basic acid-base classification, neutralisation concept
Ch 1 · Chemical Reactions & Equations
Balancing chemical equations, types of chemical reactions
Chapter 2 Acids, Bases
and Salts
Leads to
Ch 3 · Metals and Non-Metals
Reactivity series, reactions of metals with acids, ore extraction
Class 11 · Ionic Equilibrium
Ka, Kb, buffer solutions, solubility product, Henderson equation
Board Blueprint

Marks & question-type breakdown

Typical pattern based on CBSE Class 10 Science board papers from the last five years.

Question type Marks Typical count What's usually tested
MCQ / Objective 1 1–2 pH identification, indicator colour change, or salt type classification
Very Short Answer 2 1 Balanced equation for a reaction, name/formula of a salt, or dilution effect
Short Answer 3 1 Preparation of a common salt, importance of pH in daily life, or bleaching powder uses
Long Answer 4–5 1 Comprehensive question on the pH scale, or properties and uses of washing soda / baking soda
Total (approximate) 5–7 4–5 Weightage varies across paper sets and years
Sample Questions

8 sample questions — generated by MarksZen AI

Aligned to CBSE Class 10 Science Chapter 2. Covers all question types across Easy, Medium, and Hard difficulty.

Q1 Easy 1 mark MCQ
The pH of a solution is 3. Which of the following best describes the solution? (a) Strongly basic (b) Weakly basic (c) Neutral (d) Acidic
Q2 Easy 2 marks Short Answer
Write the balanced chemical equation for the reaction between dilute sulphuric acid and zinc metal. What type of reaction is this?
Q3 Medium 2 marks Short Answer
Why does dry hydrochloric acid gas not change the colour of dry litmus paper, but moist HCl gas does? Explain with reference to ionisation.
Q4 Medium 3 marks Short Answer
List three uses of baking soda (NaHCO₃). Write the chemical equation showing how baking soda reacts with a dilute acid, and name the gas produced.
Q5 Medium 3 marks Short Answer
What happens to the pH of an acidic solution when water is progressively added to it? Explain why the change in pH becomes negligible after a certain degree of dilution.
Q6 Hard 4 marks Short Answer
Describe with balanced chemical equations how washing soda (Na₂CO₃·10H₂O) is obtained from sodium chloride. State two properties and two uses of washing soda.
Q7 Hard 4 marks Word Problem
A farmer finds that the pH of his soil is 4.5. He wants to grow a crop that requires soil pH between 6 and 7. (i) What does a pH of 4.5 indicate about the soil? (ii) What substance should he add to the soil to increase its pH? (iii) Explain the chemical principle behind this treatment. (iv) Why is it harmful if the soil pH rises above 8?
Q8 Hard 5 marks Case-Based
Plaster of Paris (POP) is widely used in hospitals and construction. (i) Write the chemical formula of Plaster of Paris and its IUPAC name. (ii) Write the equation for its preparation from gypsum. (iii) What happens when POP is mixed with water? Write the equation for this reaction. (iv) Why should Plaster of Paris be stored in moisture-free containers? (v) Name one other use of Plaster of Paris besides making casts for fractured bones.
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Previous Year Questions

From CBSE board examinations

Actual questions from past Class 10 Science board papers — Acids, Bases and Salts chapter.

Board 20222 marks
A student dropped a few pieces of marble in dilute hydrochloric acid contained in a test tube. The marble pieces dissolved slowly. Write the balanced chemical equation for the reaction that takes place and name the gas evolved. (All India 2022)
Board 20233 marks
What is a neutralisation reaction? Write balanced chemical equations for two examples of neutralisation reactions. Mention one application of neutralisation in everyday life. (Delhi 2023)
Board 20205 marks
(a) What is the chemical name and formula of baking soda? (b) Write the equation for the reaction of baking soda with dilute hydrochloric acid. (c) How is baking soda converted into washing soda? Write the balanced equation. (d) State two uses of washing soda. (CBSE 2020)
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FAQ

Questions teachers ask

How many marks does Acids, Bases and Salts carry in the CBSE Class 10 board exam? +
Typically 5–7 marks across 3–4 questions — one 1-mark MCQ on pH or indicators, one 2-mark short answer on reactions or uses of salts, and one 3–5 mark question on the preparation of salts or the pH scale. This chapter appears consistently in every CBSE Class 10 Science board paper.
What are the most important chemical reactions to memorise from this chapter? +
The highest-priority reactions for board exams are: (1) Acid + Base → Salt + Water (neutralisation), (2) Acid + Metal → Salt + Hydrogen gas, (3) Acid + Metal Carbonate → Salt + CO₂ + Water, (4) Acid + Metal Bicarbonate → Salt + CO₂ + Water, and (5) the preparation of washing soda and baking soda. Students should write balanced equations with correct formulae.
How does the pH scale work and what pH values should students remember? +
The pH scale ranges from 0 to 14. A pH below 7 indicates an acidic solution, pH 7 is neutral, and pH above 7 is basic or alkaline. Key values to remember: pure water = 7, human blood ≈ 7.4, gastric juice ≈ 1–2, and baking soda solution ≈ 8–9. Board questions often ask students to identify the nature of a substance from its pH or arrange solutions in order of acidity.
What is the difference between a strong acid and a weak acid in this chapter? +
A strong acid (e.g., HCl, H₂SO₄, HNO₃) completely ionises in water, producing a high concentration of H⁺ ions and a very low pH. A weak acid (e.g., CH₃COOH, H₂CO₃) partially ionises, giving a relatively higher pH. The NCERT chapter introduces this distinction through the concept of dilution and the change in the concentration of H⁺/OH⁻ ions.
How do I generate a custom question paper for Acids, Bases and Salts using MarksZen? +
Sign up for a free MarksZen account, choose CBSE Class 10 Science, select Chapter 2 (Acids, Bases and Salts), set your preferred question-type mix (MCQ, short answer, case-based) and total marks — the AI generates a complete board-aligned paper with answer key in under 2 minutes, ready for PDF export.