Acids, Bases and Salts | Definition, Properties, Examples & Explanation (Class 9–10 Science)

🧪 Acids, Bases and Salts

📌 What are Acids, Bases and Salts?

Acids, bases and salts are important chemical substances commonly found in daily life and studied in chemistry.

👉 In simple words:

Acids → Sour substances (like lemon)
Bases → Bitter and soapy substances
Salts → Formed from reaction of acid and base

🔗 Related Topics: Chemical Reactions and Equations, pH Scale, Neutralization Reaction

🧪 What is an Acid?

An acid is a substance that releases H⁺ (hydrogen ions) in aqueous solution.

👉 Examples:

Hydrochloric acid (HCl)
Sulfuric acid (H₂SO₄)
Citric acid (in lemon)

🔍 Properties of Acids

🔸 Sour taste
🔸 Turns blue litmus red
🔸 Conduct electricity in solution
🔸 React with metals to release hydrogen gas

🧪 What is a Base?

A base is a substance that releases OH⁻ (hydroxide ions) in aqueous solution.

👉 Examples:

Sodium hydroxide (NaOH)
Calcium hydroxide (Ca(OH)₂)

🔍 Properties of Bases

🔸 Bitter taste
🔸 Slippery (soapy) feel
🔸 Turns red litmus blue
🔸 Conduct electricity

🧪 What is a Salt?

A salt is a substance formed when an acid reacts with a base (neutralization reaction).

👉 Example: Sodium chloride (NaCl)

⚖️ Neutralization Reaction

\text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water}

Example:

HCl + NaOH \rightarrow NaCl + H_2O

🧠 Key Differences

Property	Acids	Bases
Taste	Sour	Bitter
Litmus Test	Blue → Red	Red → Blue
Ions Produced	H⁺	OH⁻
Nature	Acidic	Basic

⚙️ Strength of Acids and Bases (pH Scale)

pH < 7 → Acidic
pH = 7 → Neutral
pH > 7 → Basic

👉 Lower pH = Stronger acid
👉 Higher pH = Stronger base

📊 Real-Life Applications

🧪 Acids

🍋 Citric acid in food
🏭 Sulfuric acid in batteries

🧪 Bases

🧼 Soaps and detergents
🏗️ Whitewashing (calcium hydroxide)

🧂 Salts

🍽️ Common salt (NaCl)
🧪 Baking soda

❗ Important Notes (Exam-Oriented)

⭐ Acids release H⁺ ions
⭐ Bases release OH⁻ ions
⭐ Neutralization forms salt + water
⭐ pH scale is very important
⭐ Not all salts are neutral

❓ FAQs on Acids, Bases and Salts

Q1. What is an acid?
👉 Substance that releases H⁺ ions.

Q2. What is a base?
👉 Substance that releases OH⁻ ions.

Q3. What is a salt?
👉 Product of acid and base reaction.

Q4. What is neutralization?
👉 Reaction between acid and base forming salt and water.

Q5. What is pH scale?
👉 Scale to measure acidity or basicity.

📝 Practice Questions (With Answers)

Q1. Define acid.
👉 Answer: Substance that releases H⁺ ions.

Q2. Define base.
👉 Answer: Substance that releases OH⁻ ions.

Q3. Give one example of salt.
👉 Answer: Sodium chloride.

Q4. What happens in neutralization?
👉 Answer: Acid + base → salt + water.

Q5. What is pH of neutral solution?
👉 Answer: 7

🧠 MCQ Questions (Test Yourself)

1. Acids release:
A) OH⁻
B) H⁺
C) O₂
D) CO₂
👉 Answer: B

2. Bases release:
A) H⁺
B) O₂
C) OH⁻
D) CO₂
👉 Answer: C

3. Neutralization produces:
A) Acid
B) Base
C) Salt and water
D) Gas
👉 Answer: C

4. pH of neutral solution is:
A) 0
B) 7
C) 14
D) 1
👉 Answer: B

5. Which is an acid?
A) NaOH
B) HCl
C) Ca(OH)₂
D) NaCl
👉 Answer: B

6. Which is a base?
A) HCl
B) H₂SO₄
C) NaOH
D) CO₂
👉 Answer: C

7. Which is a salt?
A) NaCl
B) HCl
C) NaOH
D) H₂
👉 Answer: A

8. Acid turns blue litmus:
A) Green
B) Red
C) Blue
D) Yellow
👉 Answer: B

9. Base turns red litmus:
A) Blue
B) Red
C) Yellow
D) Green
👉 Answer: A

10. Which has bitter taste?
A) Acid
B) Base
C) Salt
D) Water
👉 Answer: B