Acids, Bases and Salts Class 10 Notes in Hindi + English | Assertion Reason & Case Study Questions

Acids, Bases Salts Class 10: रसायन विज्ञान का अध्याय “Acids, Bases and Salts” कक्षा 10 के छात्रों के लिए बेहद महत्वपूर्ण है, क्योंकि यह न केवल बोर्ड परीक्षा में अच्छे अंक दिलाने में मदद करता है बल्कि हमारे दैनिक जीवन से भी जुड़ा हुआ है। नींबू का खट्टा स्वाद, साबुन का चिकनापन और नमक का उपयोग—all these are practical examples of acids, bases and salts. इस अध्याय में हम अम्ल, क्षार और लवण के गुण, उनके रासायनिक अभिक्रियाएं, pH स्केल, सूचक (Indicators) तथा उनके उपयोग को सरल भाषा में समझेंगे।

साथ ही इस पोस्ट में आपको Assertion-Reason प्रश्न, Case Study आधारित प्रश्न और महत्वपूर्ण उदाहरण मिलेंगे, जो आपकी परीक्षा की तैयारी को मजबूत बनाएंगे। यदि आप इस टॉपिक को आसान तरीके से समझना चाहते हैं, तो यह नोट्स आपके लिए बहुत उपयोगी साबित होंगे। For objective questions, visit Learneasily 8.

Acids Bases Salts Class 10 Notes:

In our daily life, we use many substances like lemon, soap, baking soda, etc. These substances are classified as acids, bases, and salts based on their chemical properties.

हम अपने दैनिक जीवन में नींबू, साबुन, बेकिंग सोडा जैसी चीज़ों का उपयोग करते हैं। इनके रासायनिक गुणों के आधार पर इन्हें अम्ल (Acids), क्षार (Bases) और लवण (Salts) में वर्गीकृत किया जाता है।

Acids (अम्ल)

Definition

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

अम्ल वे पदार्थ हैं जो पानी में घुलकर H⁺ आयन उत्पन्न करते हैं।

Examples

• HCl (Hydrochloric acid)
• H₂SO₄ (Sulphuric acid)
• HNO₃ (Nitric acid)

Properties (गुण)

• Sour taste (खट्टा स्वाद)
• Turn blue litmus red (नीले लिटमस को लाल करते हैं)
• Conduct electricity in solution
• React with metals to produce hydrogen gas

Reaction Example:

Zn + 2HCl → ZnCl₂ + H₂↑

Bases and Alkalis (क्षार)

Definition

Bases are substances that produce OH⁻ ions in solution.
Alkalis are bases that dissolve in water.

क्षार वे पदार्थ हैं जो पानी में OH⁻ आयन उत्पन्न करते हैं।
जो क्षार पानी में घुल जाते हैं उन्हें Alkali (क्षारीय) कहते हैं।

Examples

• NaOH (Sodium hydroxide)
• KOH (Potassium hydroxide)
• Ca(OH)₂ (Calcium hydroxide)

Properties

• Bitter taste (कड़वा स्वाद)
• Soapy touch (चिकना स्पर्श)
• Turn red litmus blue (लाल लिटमस को नीला करते हैं)

Read Also: Chemical Reactions and Chemical Equations Class 10 Notes (Hindi + English)

Salts (लवण)

Definition

Salts are formed by the neutralization reaction between an acid and a base.

लवण अम्ल और क्षार के उदासीनीकरण (Neutralization) से बनते हैं।

Example

HCl + NaOH → NaCl + H₂O

Strength of Acids and Bases (मजबूती)

Strong vs Weak

Type	Example	Explanation
Strong Acid	HCl	Fully ionizes
Weak Acid	CH₃COOH	Partially ionizes
Strong Base	NaOH	Fully ionizes
Weak Base	NH₄OH	Partially ionizes

pH Scale (pH पैमाना)

• Range: 0 to 14
• pH < 7 → Acid
• pH = 7 → Neutral
• pH > 7 → Base

Important Values:

• Lemon → pH ~ 2
• Water → pH = 7
• Soap → pH ~ 10

Chemical Properties

Reaction with Metals

Acid + Metal → Salt + Hydrogen gas

Example:
Zn + H₂SO₄ → ZnSO₄ + H₂

Reaction with Metal Carbonates

Acid + Carbonate → Salt + CO₂ + H₂O

Example:
Na₂CO₃ + 2HCl → 2NaCl + CO₂ + H₂O

Neutralization Reaction

Acid + Base → Salt + Water

Example:
HCl + NaOH → NaCl + H₂O

Indicators (सूचक)

Types:

Indicator	Acid	Base
Litmus	Red	Blue
Phenolphthalein	Colorless	Pink
Methyl Orange	Red	Yellow

Important Concepts

Dilution (तनुकरण)

• Always add acid to water (Never reverse)
  👉 Safety rule: “Do as you oughtta, add acid to water”

Universal Indicator

• Shows different colors for different pH values

Tooth Decay

• pH < 5.5 causes tooth decay
• Toothpaste is basic to neutralize acid

Common Salts and Their Uses

Baking Soda (NaHCO₃)

• Used in baking
• Makes cakes soft

Washing Soda (Na₂CO₃·10H₂O)

• Used for cleaning
• Softening hard water

Bleaching Powder (CaOCl₂)

• Used for bleaching clothes
• Disinfecting water

Plaster of Paris (CaSO₄·½H₂O)

• Used for making statues and casts

Water of Crystallization

Definition:
Water molecules present in crystals of salts.

Example:
CuSO₄·5H₂O (Blue vitriol)

Important Reactions

1. Formation of Plaster of Paris:
   CaSO₄·2H₂O → CaSO₄·½H₂O + H₂O
2. Heating Baking Soda:
   2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O

Key Points (Revision)

• Acids give H⁺ ions
• Bases give OH⁻ ions
• pH tells strength
• Neutralization forms salt + water
• Indicators show acidic/basic nature

Assertion–Reason Questions

(Class 10 – Acids, Bases and Salts)

👉 Instruction:
(A) Both Assertion and Reason are true, and Reason is the correct explanation
(B) Both true, but Reason is NOT correct explanation
(C) Assertion true, Reason false
(D) Assertion false, Reason true

Q1.
Assertion: Acids conduct electricity in aqueous solution.
Reason: Acids produce ions in water.
Answer: A

Q2.
Assertion: Dry HCl gas does not change blue litmus paper.
Reason: HCl gas does not produce H⁺ ions without water.
Answer: A

Q3.
Assertion: All bases are alkalis.
Reason: Alkalis are bases soluble in water.
Answer: D

Q4.
Assertion: Strong acids have low pH values.
Reason: Strong acids completely ionize in solution.
Answer: A

Q5.
Assertion: NaOH is a strong base.
Reason: It partially dissociates in water.
Answer: C

Q6.
Assertion: Phenolphthalein turns pink in basic solution.
Reason: It is an indicator.
Answer: B

Q7.
Assertion: Tooth decay occurs when pH is below 5.5.
Reason: Acidic medium damages enamel.
Answer: A

Q8.
Assertion: Neutralization reaction produces salt and water.
Reason: Acid reacts with base.
Answer: A

Q9.
Assertion: Weak acids are less dangerous than strong acids.
Reason: Weak acids partially ionize.
Answer: B

Q10.
Assertion: Washing soda is used to soften hard water.
Reason: It reacts with calcium and magnesium salts.
Answer: A

Case Study Questions

Case Study 1: Lemon Juice and Soap

Ravi tested lemon juice and soap solution using litmus paper. Lemon juice turned blue litmus red, while soap turned red litmus blue.

Questions:

Q1. What is the nature of lemon juice?
Answer: Acidic

Q2. Why does soap turn red litmus blue?
Answer: Because it is basic

Q3. Which ions are present in lemon juice?
Answer: H⁺ ions

Q4. Which substance has higher pH?
Answer: Soap solution

Case Study 2: Reaction with Metal

A student added dilute HCl to zinc granules. A gas was evolved.

Questions:

Q1. Name the gas evolved.
Answer: Hydrogen

Q2. Write the reaction.
Answer: Zn + 2HCl → ZnCl₂ + H₂

Q3. What type of reaction is this?
Answer: Metal + Acid reaction

Q4. How can you test hydrogen gas?
Answer: By burning it (pop sound test)

Case Study 3: Tooth Decay

A person frequently eats sweets and does not brush properly.

Questions:

Q1. What happens to mouth pH?
Answer: It decreases (becomes acidic)

Q2. Below which pH tooth decay starts?
Answer: 5.5

Q3. Why toothpaste is basic?
Answer: To neutralize acids

Q4. Suggest one prevention method.
Answer: Regular brushing

Case Study 4: Baking Soda Heating

When baking soda is heated, it forms sodium carbonate, CO₂ and water.

Questions:

Q1. Write the reaction.
Answer: 2NaHCO₃ → Na₂CO₃ + CO₂ + H₂O

Q2. Why cakes become fluffy?
Answer: CO₂ gas is released

Q3. Nature of sodium carbonate?
Answer: Basic

Q4. Type of reaction?
Answer: Thermal decomposition

Short FAQs (Hindi + English)

Q1. What is an acid? / अम्ल क्या है?
Acid is a substance that produces H⁺ ions in water.

Q2. What is pH scale? / pH स्केल क्या है?
It measures acidity or basicity from 0 to 14.

Q3. What is neutralization? / उदासीनीकरण क्या है?
Reaction between acid and base forming salt and water.

Q4. Why should acids be diluted carefully?
Because reaction produces heat and may cause burns.

Conclusion (निष्कर्ष)

Acids, bases, and salts are very important in chemistry and daily life. Understanding their properties helps in solving real-life problems.

अम्ल, क्षार और लवण रसायन विज्ञान और हमारे दैनिक जीवन में बहुत महत्वपूर्ण हैं। इनके गुणों को समझना हमें व्यावहारिक जीवन में मदद करता है।