Revision Notes: Class 10 Science Chapter 2 Acids, Bases and Salts

A fast, one-glance recap of Class 10 Science Chapter 2 (Acids, Bases and Salts) — for the full worked explanations, see the Solutions. These Class 10 Science Chapter 2 notes are ideal for quick revision just before exams.

Last Updated: October 24, 2026

Common Mistakes Students Make in Acids, Bases and Salts

Why This Chapter Matters

Acids, Bases and Salts is one of the standard chapters in the CBSE/NCERT Class 10 Science syllabus and questions from it appear regularly in board exams, in formats ranging from 1-mark objective questions to longer 3-5 mark descriptive or numerical questions. Because the concepts here often build on earlier chapters (and feed into later ones), a solid grip on this chapter also makes the rest of the Science syllabus easier to follow.

Revision Notes: Acids, Bases and Salts

• Acid: releases H⁺ (as H₃O⁺) ions in water — e.g. HCl, H₂SO₄, CH₃COOH
• Base: releases OH⁻ ions in water — e.g. NaOH, KOH, Ca(OH)₂
• Indicators: litmus (red↔blue), phenolphthalein (colourless in acid, pink in base), methyl orange; olfactory indicators like onion/vanilla/clove oil lose their smell in base
• Acid + Metal → Salt + H₂↑ (test: burning splinter gives a pop sound)
• Metal carbonate/bicarbonate + Acid → Salt + CO₂↑ + H₂O (test: CO₂ turns lime water milky)
• Acid + Base → Salt + Water (neutralisation); ionically just H⁺ + OH⁻ → H₂O
• Metallic oxide + Acid → Salt + Water (metallic oxides are basic in nature)
• Non-metallic oxide + Base → Salt + Water (non-metallic oxides are acidic in nature)
• Strong vs weak: strong acids/bases ionise almost completely (HCl, NaOH); weak ones ionise only partially (CH₃COOH, NH₄OH)
• pH scale: 0–14; <7 acidic, =7 neutral, >7 basic; lower pH = higher H⁺ concentration
• pH matters for: soil health, digestion (stomach HCl), tooth decay (enamel erodes below pH 5.5), and plant/animal survival (narrow pH range)
• Water of crystallisation: fixed water molecules per formula unit, e.g. CuSO₄·5H₂O, Na₂CO₃·10H₂O
• Common salts: NaCl (table salt), NaOH (chlor-alkali process), Na₂CO₃·10H₂O (washing soda), NaHCO₃ (baking soda), CaOCl₂ (bleaching powder), CaSO₄·½H₂O (Plaster of Paris)
• Bleaching powder: Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
• Plaster of Paris: gypsum (CaSO₄·2H₂O) heated at ~373 K → CaSO₄·½H₂O + 1½H₂O

See also: Extra Questions (HOTS) | Class 10 Science Key Reactions Handbook

How to Use These Notes

These revision notes are meant for quick recall in the last few days before an exam or unit test — they are not a substitute for first reading the full chapter and working through examples in the NCERT textbook. A good routine is: read the chapter once, solve the in-text and end-of-chapter questions using the linked Solutions, then come back to this page a day or two before the exam to refresh the key definitions and formulas without re-reading the whole chapter.

Frequently Asked Questions

What is the pH scale, and what do its values indicate?
The pH scale runs from 0 to 14 and measures how acidic or basic a solution is: values below 7 indicate acidic, exactly 7 indicates neutral, and above 7 indicates basic — it is a logarithmic scale, so each whole-number change represents a tenfold change in acidity/basicity.

What is the difference between a strong acid/base and a weak acid/base?
A strong acid or base ionises almost completely in water, producing a high concentration of H+ or OH- ions; a weak acid or base ionises only partially, producing fewer ions — strength is about the degree of ionisation, not the concentration of the solution.

What to Revise First (and Last) in This Chapter

Written by Satish

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