Introduction | परिचय

Acids, bases and salts are important chemical substances used in laboratories, industries, medicines and daily life. This chapter explains their properties, reactions, pH scale and applications. (Class 10 Science )

अम्ल, क्षार और लवण महत्वपूर्ण रासायनिक पदार्थ हैं जिनका उपयोग प्रयोगशाला, उद्योग, दवाइयों तथा दैनिक जीवन में किया जाता है। इस अध्याय में इनके गुण, अभिक्रियाएँ, pH स्केल तथा उपयोगों का अध्ययन किया जाता है।

What are Acids? | अम्ल क्या हैं?

Acids are substances that produce hydrogen ions (H⁺) in aqueous solution.

जो पदार्थ जलीय विलयन में H⁺ आयन देते हैं उन्हें अम्ल कहते हैं।

Examples of Acids

Acid Name	Chemical Formula	Common Use
Hydrochloric Acid	HCl	Stomach acid
Sulphuric Acid	H₂SO₄	Car batteries
Nitric Acid	HNO₃	Fertilizers
Acetic Acid	CH₃COOH	Vinegar

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Physical Properties of Acids | अम्लों के भौतिक गुण

Properties in English	हिंदी में
Sour in taste	स्वाद में खट्टे
Turn blue litmus red	नीले लिटमस को लाल करते हैं
Conduct electricity	विद्युत का संचालन करते हैं
Corrosive in nature	संक्षारक प्रकृति
React with metals	धातुओं से अभिक्रिया करते हैं

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Chemical Properties of Acids | अम्लों के रासायनिक गुण

1. Reaction with Metals

Acids react with metals to form salt and hydrogen gas.

अम्ल धातुओं से अभिक्रिया करके लवण और हाइड्रोजन गैस बनाते हैं।

$Zn + 2HCl \rightarrow ZnCl_2 + H_2\uparrow$Zn+2HCl→ZnCl2​+H2​↑

Observation

• Bubbles of hydrogen gas are produced.
• Zinc chloride salt is formed.

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2. Reaction with Metal Carbonates

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

$CaCO_3 + 2HCl \rightarrow CaCl_2 + CO_2 + H_2O$CaCO3​+2HCl→CaCl2​+CO2​+H2​O

Important Observation

Carbon dioxide gas turns lime water milky.

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What are Bases? | क्षार क्या हैं?

Bases are substances that produce hydroxide ions (OH⁻) in aqueous solution.

जो पदार्थ जलीय विलयन में OH⁻ आयन देते हैं उन्हें क्षार कहते हैं।

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Properties of Bases | क्षारों के गुण

Properties	हिंदी में
Bitter in taste	स्वाद में कड़वे
Soapy to touch	साबुन जैसे चिकने
Turn red litmus blue	लाल लिटमस को नीला करते हैं
Conduct electricity	विद्युत चालक
Neutralize acids	अम्ल को उदासीन करते हैं

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Strong and Weak Acids & Bases (Class 10 Science )

Type	Examples	Characteristics
Strong Acids	HCl, H₂SO₄	Completely ionize
Weak Acids	CH₃COOH	Partially ionize
Strong Bases	NaOH, KOH	Completely ionize
Weak Bases	NH₄OH	Partially ionize

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Acid-Base Indicators | अम्ल-क्षार संकेतक

Indicators are substances that show different colors in acidic and basic solutions.

संकेतक ऐसे पदार्थ हैं जो अम्लीय एवं क्षारीय विलयन में अलग-अलग रंग प्रदर्शित करते हैं।

Types of Indicators (Class 10 Science )

Indicator	Acidic Medium	Basic Medium
Litmus	Red	Blue
Phenolphthalein	Colorless	Pink
Methyl Orange	Red	Yellow

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Natural Indicators | प्राकृतिक संकेतक

Natural Indicator	Acidic Color	Basic Color
Turmeric	Yellow	Reddish Brown
China Rose	Dark Pink	Green
Red Cabbage	Red	Greenish Yellow

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Neutralization Reaction | उदासीनीकरण अभिक्रिया

The reaction between an acid and a base to form salt and water is called neutralization reaction.

अम्ल और क्षार की अभिक्रिया से लवण और जल बनने की प्रक्रिया को उदासीनीकरण कहते हैं।

$HCl + NaOH \rightarrow NaCl + H_2O$HCl+NaOH→NaCl+H2​O

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pH Scale | pH स्केल

The pH scale is used to measure acidity or basicity of a solution.

pH स्केल का उपयोग किसी विलयन की अम्लीयता या क्षारीयता मापने के लिए किया जाता है।

$pH = -\log[H^+]$pH=−log[H+]

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Importance of pH Scale

Situation	Importance
Digestion	Stomach contains HCl
Tooth decay	pH below 5.5 damages teeth
Agriculture	Soil pH affects crop growth
Human body	Blood pH must remain stable

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Universal Indicator and pH Values

pH Value	Nature
0 – 3	Strong Acid
4 – 6	Weak Acid
7	Neutral
8 – 11	Weak Base
12 – 14	Strong Base

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What are Salts? | लवण क्या हैं? (Class 10 Science )

Salts are ionic compounds formed during neutralization reaction.

लवण आयनिक यौगिक हैं जो उदासीनीकरण अभिक्रिया में बनते हैं।

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Types of Salts (Class 10 Science )

Salt Type	Example
Neutral Salt	NaCl
Acidic Salt	NaHSO₄
Basic Salt	Mg(OH)Cl

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Common Salt (Sodium Chloride)

Chemical Formula:

$NaCl$NaCl

Uses

• Food preservation
• Cooking
• Manufacturing chemicals

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Baking Soda

Chemical Formula:

$NaHCO_3$NaHCO3​

Preparation

$NaCl + NH_3 + CO_2 + H_2O \rightarrow NaHCO_3 + NH_4Cl$NaCl+NH3​+CO2​+H2​O→NaHCO3​+NH4​Cl

Uses of Baking Soda

Uses	Explanation
Baking cakes	Produces CO₂
Fire extinguisher	Releases CO₂
Antacid	Neutralizes acidity

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Washing Soda

Chemical Formula:

$Na_2CO_3\cdot10H_2O$Na2​CO3​⋅10H2​O

Uses

Uses	Application
Cleaning agent	Washing clothes
Removes hardness	Softens water
Industry use	Glass, soap, paper

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Bleaching Powder

Chemical Formula:

$CaOCl_2$CaOCl2​

Uses

• Disinfecting drinking water
• Bleaching cotton and linen
• Used in paper industries

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Plaster of Paris (POP)

Chemical Formula:

$CaSO_4\cdot\frac{1}{2}H_2O$CaSO4​⋅21​H2​O

Uses of POP

Uses	Example
Orthopedic plaster	Bone fracture
Decorative items	Statues
Construction	False ceiling

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Important Chemical Equations (Class 10 Science )

Reaction	Equation
Acid + Metal	Zn + 2HCl → ZnCl₂ + H₂
Neutralization	HCl + NaOH → NaCl + H₂O
Baking Soda Heating	2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O
Lime Water Test	Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

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Important NCERT Questions

Very Short Answer Questions

1. Define pH scale.
2. Name one strong acid.
3. Why does tooth decay occur?

Short Answer Questions

1. Explain neutralization reaction with equation.
2. Differentiate between acids and bases.
3. Explain the importance of pH in everyday life.

Long Answer Questions

1. Describe preparation and uses of baking soda.
2. Explain properties of acids with chemical equations.
3. What are salts? Explain types and uses of salts.

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Conclusion | निष्कर्ष (Class 10 Science )

Acids, bases and salts play an important role in chemistry as well as daily life. Their reactions, pH values and industrial applications are essential concepts for Class 10 students and competitive exams. Keep learning with Rising Star Mindset your daily study partner.

अम्ल, क्षार और लवण रसायन विज्ञान तथा दैनिक जीवन का महत्वपूर्ण भाग हैं। इनके गुण, pH मान तथा औद्योगिक उपयोग Class 10 और प्रतियोगी परीक्षाओं के लिए अत्यंत महत्वपूर्ण हैं।

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