The NDA (National Defence Academy) & CDS (Combined Defence Services) Exams are conducted by UPSC to recruit candidates for the Indian Armed Forces. The written exam tests core subjects including Mathematics, English, General Knowledge, and General Science (Physics, Chemistry & Biology).
In Chemistry, questions are mainly conceptual, basic, and application-based, often asked in MCQ format. Understanding fundamental principles is essential for scoring well in the General Knowledge section.
1. Acids, Bases and Salts – Overview
Introduction
Acids, bases, and salts are fundamental chemical substances that play key roles in daily life and industrial processes. NDA/CDS exams frequently test their properties, examples, reactions, and applications.
Subtopics
- Definition and Characteristics
- Properties of acids (taste, pH, reactions)
- Properties of bases (feel, reaction with indicators)
- Salts as neutralization products
- Types of Acids and Bases
- Strong vs weak acids
- Strong vs weak bases
- Mineral acids vs organic acids
- pH Scale
- Meaning of pH
- Acidic, basic, and neutral solutions
- Importance of pH in daily life
- Indicators
- Litmus, phenolphthalein, methyl orange
- Natural indicators
- Neutralization Reactions
- Acid + Base → Salt + Water
- Applications (antacids, agriculture, industry)
- Common Salts and Their Uses
- Sodium chloride, baking soda, washing soda, plaster of Paris
- Chemical formulas and uses
Conclusion
Understanding acids, bases, and salts helps decode many real-life reactions and is a high-yield topic for NDA/CDS exams. Mastery of their properties and examples ensures strong command over basic chemistry.
2. Elements, Compounds and Mixtures – Overview
Introduction
Matter exists in various forms, and its classification into elements, compounds, and mixtures forms the foundation of chemistry. NDA/CDS MCQs often test definitions, differences, and examples.
Subtopics
- Elements
- Definition and characteristics
- Metals, non-metals, metalloids
- Common examples and uses
- Compounds
- Chemical bonding and fixed composition
- Examples: water, carbon dioxide, sodium chloride
- Difference between compounds and mixtures
- Mixtures
- Homogeneous vs heterogeneous mixtures
- Examples: air, salt solution, sand & iron fillings
- Methods of Separation of Mixtures
- Filtration
- Evaporation
- Distillation
- Sublimation
- Chromatography
- Chemical & Physical Changes
- Identifying features
- Real-world examples
Conclusion
A clear understanding of elements, compounds, and mixtures helps build a strong conceptual foundation in chemistry. These basics are repeatedly tested in NDA/CDS and form the base for further chemical study.
Shivangi Srivastava
