CBSE Class 10 Science Revision Notes Chapter 2 Acids, Bases and Salts 2026–27

Acids, Bases and Salts explains how substances behave in acidic, basic and neutral solutions. In CBSE Class 10 Science, Chapter 2 covers indicators, reactions, pH scale, salts and chemicals from common salt.

Acids, Bases, and Salts form an important chemistry chapter in Class 10 Science. The chapter explains how acids and bases react, how indicators identify them, and how salts are formed from neutralisation reactions.

Use these CBSE Class 10 Science Revision Notes Chapter 2 to revise the chapter for the 2026–27 exams. Start with definitions, then revise indicators, chemical reactions, pH scale, common salt compounds and Plaster of Paris.

Key Takeaways

• Acids: Acids produce H⁺ ions in water and turn blue litmus red.
• Bases: Bases produce OH⁻ ions in water and turn red litmus blue.
• pH scale: A pH below 7 is acidic, pH 7 is neutral and pH above 7 is basic.
• Common salt: Sodium chloride gives important compounds such as sodium hydroxide, bleaching powder, baking soda and washing soda.

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CBSE Class 10 Science Revision Notes Chapter 2 at a Glance

Chapter 2 connects daily-use substances with chemical reactions. Lemon juice, soap, toothpaste, baking soda and common salt all help explain acids, bases and salts.

These Class 10 Science Chapter 2 Notes help students revise definitions, reactions and formulas in one place.

What Are Acids, Bases and Salts?

Acids are substances that produce hydrogen ions in water. They taste sour and turn blue litmus paper red.

Examples of acids include hydrochloric acid, sulphuric acid, nitric acid, acetic acid and citric acid.

Bases are substances that produce hydroxide ions in water. They taste bitter, feel soapy and turn red litmus paper blue.

Examples of bases include sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonium hydroxide.

Salts are formed when an acid reacts with a base. This reaction forms salt and water.

Acid + Base → Salt + Water

Example:

HCl + NaOH → NaCl + H₂O

This reaction is called a neutralisation reaction.

Difference Between Acids, Bases and Salts

Acids, bases and salts can be compared through taste, litmus test, ions and pH. This table gives a quick revision view.

Do not taste chemicals in the laboratory. Some acids and bases are corrosive.

Indicators for Acids and Bases

Indicators help identify whether a substance is acidic or basic. They show a colour change or smell change in different solutions.

Litmus is a natural indicator obtained from lichens. It is one of the most common indicators used in Chapter 2 Science Class 10 Notes.

Olfactory indicators change smell in acidic or basic solutions. Onion, vanilla essence and clove oil are common examples.

Chemical Properties of Acids and Bases

Acids and bases show their chemical nature through reactions. These reactions help students identify products quickly in exam questions.

Reaction of Acids with Metals

Acids react with metals to form salt and hydrogen gas.

Acid + Metal → Salt + Hydrogen gas

Example:

2HCl + Zn → ZnCl₂ + H₂

Hydrogen gas can be tested by bringing a burning candle near it. The gas burns with a pop sound.

Reaction of Acids with Metal Carbonates

Acids react with metal carbonates to form salt, water and carbon dioxide.

Acid + Metal carbonate → Salt + Water + Carbon dioxide

Example:

Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

Carbon dioxide turns lime water milky.

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Reaction of Acids with Metal Hydrogen Carbonates

Acids react with metal hydrogen carbonates to form salt, water and carbon dioxide.

Acid + Metal hydrogen carbonate → Salt + Water + Carbon dioxide

Example:

NaHCO₃ + HCl → NaCl + H₂O + CO₂

This reaction also shows brisk effervescence due to carbon dioxide gas.

Reaction of Acids with Bases

Acids react with bases to form salt and water. This is called a neutralisation reaction.

Acid + Base → Salt + Water

Example:

HCl + NaOH → NaCl + H₂O

Neutralisation is used in many daily-life situations, such as treating acidity with antacids.

Reaction of Acids with Metal Oxides

Metal oxides are basic in nature. They react with acids to form salt and water.

Metal oxide + Acid → Salt + Water

Example:

CuO + 2HCl → CuCl₂ + H₂O

Copper oxide is black, while copper chloride solution is blue-green.

Reaction of Bases with Non-Metal Oxides

Non-metal oxides are acidic in nature. They react with bases to form salt and water.

Base + Non-metal oxide → Salt + Water

Example:

2NaOH + CO₂ → Na₂CO₃ + H₂O

This reaction shows that non-metal oxides behave like acids.

Reaction of Bases with Metals

Some bases react with metals such as zinc to form salt and hydrogen gas.

Base + Metal → Salt + Hydrogen gas

Example:

2NaOH + Zn → Na₂ZnO₂ + H₂

Here, sodium zincate and hydrogen gas are formed.

What Happens When Acids and Bases Dissolve in Water?

Acids produce H⁺ ions in water. These hydrogen ions combine with water molecules to form hydronium ions.

H⁺ + H₂O → H₃O⁺

Bases produce OH⁻ ions in water.

NaOH → Na⁺ + OH⁻

Acids show acidic behaviour only in water because H⁺ ions are formed in aqueous solution.

Dilution means adding water to an acid or base. It decreases the concentration of H₃O⁺ or OH⁻ ions per unit volume.

Dilution of acids and bases is exothermic. Always add acid to water slowly with constant stirring.

Strong and Weak Acids and Bases

The strength of an acid or base depends on how many ions it produces in water. This is different from concentration.

A concentrated acid has more acid in less water. A dilute acid has less acid in more water.

pH Scale in Acids, Bases and Salts

The pH scale measures the concentration of hydrogen ions in a solution. It ranges from 0 to 14.

A lower pH means a stronger acidic nature. A higher pH means a stronger basic nature.

Pure water has pH 7. It is neutral.

pH = -log[H⁺]

The pH scale is tested using universal indicator or pH paper.

Importance of pH in Everyday Life

The pH concept explains many daily-life processes. It connects chemistry with the human body, plants, soil and oral health.

Toothpaste is basic in nature. It helps neutralise acids formed in the mouth.

Salts and Family of Salts

Salts are ionic compounds formed from acids and bases. They contain positively charged ions and negatively charged ions.

NaCl contains Na⁺ and Cl⁻ ions.

Salts that have the same positive or negative ions belong to the same family.

Examples:

NaCl, KCl and LiCl belong to the same chloride family.

NaNO₃ and KNO₃ belong to the nitrate family.

The pH of a salt depends on the acid and base from which it is formed.

Chemicals from Common Salt

Common salt is sodium chloride. It is used to prepare several important chemicals.

These CBSE Notes Class 10 Science Chapter 2 compounds are important for formula-based revision.

Sodium Hydroxide from Common Salt

Sodium hydroxide is also called caustic soda. It is prepared by electrolysis of brine.

Brine is an aqueous solution of sodium chloride.

2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + Cl₂(g) + H₂(g)

Chlorine gas is released at the anode. Hydrogen gas is released at the cathode.

Sodium hydroxide remains in the solution.

This process is called the chlor-alkali process because chlorine and alkali are formed.

Bleaching Powder

Bleaching powder is prepared by passing chlorine over dry slaked lime.

Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

The chemical formula of bleaching powder is CaOCl₂.

Uses of bleaching powder:

• Bleaching cotton and linen in the textile industry
• Bleaching wood pulp in paper factories
• Disinfecting drinking water
• Acting as an oxidising agent in chemical industries

Baking Soda

Baking soda is sodium hydrogen carbonate. Its chemical formula is NaHCO₃.

It is prepared using sodium chloride, water, carbon dioxide and ammonia.

NaCl + H₂O + CO₂ + NH₃ → NH₄Cl + NaHCO₃

Uses of baking soda:

• Making baking powder
• Neutralising stomach acidity as an antacid
• Used in soda-acid fire extinguishers

When heated, baking soda gives sodium carbonate, water and carbon dioxide.

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

Washing Soda

Washing soda is sodium carbonate decahydrate. Its formula is Na₂CO₃·10H₂O.

It is obtained by recrystallisation of sodium carbonate.

Na₂CO₃ + 10H₂O → Na₂CO₃·10H₂O

Uses of washing soda:

• Used for washing clothes
• Used to soften hard water
• Used in glass, soap and paper industries

Washing soda is a basic salt.

Water of Crystallisation and Plaster of Paris

Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt.

Examples:

CuSO₄·5H₂O is hydrated copper sulphate.

Na₂CO₃·10H₂O is washing soda.

CaSO₄·2H₂O is gypsum.

Plaster of Paris is calcium sulphate hemihydrate.

Its formula is CaSO₄·1/2H₂O.

It is prepared by heating gypsum at 373 K.

CaSO₄·2H₂O → CaSO₄·1/2H₂O + 3/2H₂O

Plaster of Paris becomes hard when mixed with water. It changes back into gypsum.

Formula Table for Acids Bases and Salts Class 10

This table gives the main reactions and formulas from Class 10 Chapter 2 Science Notes.

Chapter 2 Acids, Bases and Salts Summary

Acids produce H⁺ ions in water, while bases produce OH⁻ ions. Indicators help identify whether a solution is acidic or basic.

Acids react with metals to produce hydrogen gas. They react with carbonates and hydrogen carbonates to produce carbon dioxide.

Acids and bases react to form salt and water. This is called neutralisation.

The pH scale measures acidic or basic nature. It ranges from 0 to 14.

Common salt gives important chemicals such as sodium hydroxide, bleaching powder, baking soda and washing soda. These Acids Bases and Salts Class 10 notes also cover water of crystallisation and Plaster of Paris.

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