‘रचना-प्रयोग’ का मुख्य उद्देश्य क्या है?

व्याकरण का व्यावहारिक प्रयोग सिखाना

‘द्वितीयः’ किस प्रकार की संख्या है?

क्रमवाचक (दूसरा)

What happens to the pH when an acid is diluted with water?

The concentration of H⁺ ions per unit volume decreases, so the pH rises slightly towards 7.

Why does dry HCl gas not turn blue litmus red?

Because it does not release H⁺ ions in the absence of water; acidic behaviour needs water to ionise.

How do acids and bases behave in water?

Acids produce hydrogen ions (H⁺) in water while bases produce hydroxide ions (OH⁻); water-soluble bases are called alkalis.

What are indicators? Name a few.

Substances that show whether a solution is acidic or basic by a change of colour or smell, such as litmus, phenolphthalein, methyl orange and olfactory indicators like onion.

What is the pH scale, and why is it important?

A scale from 0 to 14 measuring the acidity or basicity of a solution (7 is neutral); it matters in digestion, soil for crops, tooth decay and survival of organisms.

How do acids react with metals and with metal carbonates?

Acids react with active metals to give a salt and hydrogen gas, and with metal carbonates/bicarbonates to give a salt, water and carbon dioxide.

What is neutralisation? Give the general reaction.

The reaction between an acid and a base to form salt and water: acid + base → salt + water; the acidic and basic natures cancel out.

How are baking soda and washing soda made and used?

Baking soda (sodium hydrogencarbonate) is made from brine, ammonia and CO₂, and used in cooking and antacids; washing soda (sodium carbonate) is got from baking soda and used for cleaning and softening water.

What is bleaching powder, and how is it prepared?

Calcium oxychloride, prepared by passing chlorine over dry slaked lime; it is used for bleaching and disinfecting water.

What is water of crystallisation? Give an example.

A fixed number of water molecules present in one formula unit of a salt, e.g. copper sulphate crystals (CuSO₄·5H₂O), which turn white on heating.

Acids, Bases and Salts

Class 10 Science · Chapter 2

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Summary

Acids release hydrogen ions (H⁺) in water, while bases release hydroxide ions (OH⁻); alkalis are water-soluble bases. We identify them using indicators such as litmus, phenolphthalein and methyl orange, and we measure their strength on the pH scale from 0 to 14, where 7 is neutral. When an acid reacts with a base, neutralisation occurs, producing a salt and water. Acids and bases also react with metals, metal carbonates and metal oxides in predictable ways. The chapter studies several important salts — common salt, sodium hydroxide, bleaching powder, baking soda, washing soda and plaster of Paris — explaining how each is made and used. It also introduces the idea of water of crystallisation, the fixed number of water molecules in a salt’s crystal structure, as in hydrated copper sulphate.

Acids, bases and indicatorspH scale and its importanceNeutralisation reactionsReactions of acids and basesImportant salts and their uses

Key terms

pH scale

A 0–14 scale measuring acidity (low) or basicity (high); 7 is neutral.

Neutralisation

Reaction of an acid with a base to give salt and water.

Indicator

A substance that changes colour to show acidic or basic nature.

Water of crystallisation

Fixed water molecules present in a crystalline salt.

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Acids release which ion when dissolved in water?

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Acids, Bases and Salts

CBSE Class 10 Board Examination community

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