Class 8 General Science Notes: - Unit-7: Acid, Base and Salt : Solved Exercise (Long Questions and Answers)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

C. Long Questions

Q1. Describe acids and bases with at least three examples.

Ans:

Acid: An acid is a substance that gives Hydrogen ions (H⁺) when dissolved in water. Acids have a sour taste.

Examples: HCl, H₂SO₄, and carbonic acid (H₂CO₃) are mineral acids. Acetic acid CH₃COOH and formic acid (HCOOH) are organic acids.

Base: A compound that has a bitter taste is called a base. A base that is dissolved in water is called an alkali. Alkalis are compounds that produced hydroxide ions (OH⁻) when dissolved in water.

Examples:

NaOH Sodium hydroxide, Potassium hydroxide, etc.

NaOH ⟶ Na⁺ + OH⁻

KOH ⟶ K⁺ + OH⁻

Q2. Differentiate between strong and weak acids with examples.

Ans:

Acids are classified on the basis of ionizing capacity.

Strong Acids: Acids that ionize in water completely are called strong acids.

For Example HCl, H₂SO₄, HNO₃, etc.

Weak Acids: Acids that do not ionize in water completely are called weak acids.

For example Vinegar, Formic acid, Carbonic acid, etc.

Q3. Give examples of strong and weak bases.

Ans:

Alkalis are classified on the basis of ionizing capacity.

Strong Alkalis: Alkalis that ionize in water completely are called strong alkalis:

For example NaOH, KOH.

Weak Alkalis: Alkalis that do not ionize in water completely are called weak alkalis.

For example: NH₄OH, Cu(OH)₂, Al(OH)₃ etc

Unit-7: Acid, Base and Salt: Solved Short Questions and Answers

Class 8 General Science Notes

Source: General Science Book (National Book Foundation, Pakistan)

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