By SenaPrep Defence Team Updated July 2026 8 min read
Cracking the UPSC National Defence Academy (NDA) written examination requires a highly focused preparation timeline. In this comprehensive study guide, our defence education experts analyze the core concepts of alloys composition NDA, metals nonmetals reactivity, GAT elements notes, outline high-yield preparation tips, and provide step-by-step examples.
Part 1: Understanding NDA Chemistry: Metals, Non-Metals & Alloys
The written examination conducted by the Union Public Service Commission (UPSC) is highly competitive. Every year, over 3 lakh candidates compete for less than 400 vacancies. To secure your name in the final recommendation list, you must clear the sectional cutoffs and score highly in both Papers.
Syllabus Breakdown & Marks Allocation
Subject Segment
Total Questions
Weightage (Marks)
Preparation Priority
Paper 1: Mathematics
120 Questions
300 Marks
Critical (Sectional Cutoff)
Paper 2: GAT (English)
50 Questions
200 Marks
High Yield (4 Marks/Q)
Paper 2: GAT (General Knowledge)
100 Questions
400 Marks
High Scoring (Science & GS)
Part 2: Key Revision Strategies for alloys composition NDA, metals nonmetals reactivity, GAT elements notes
Success in this topic requires consistent daily practice. Here are the core routines recommended by top defence educators:
Build Foundational Concepts: Rely on Class 11 and 12 NCERT books for math/science topics, and read standard grammar texts for English.
Solve Previous Year Papers (PYQs): Go through at least the last 5-10 years of UPSC question sets to analyze repeat question structures.
Speed & Time Management: Practice mock tests with a timer to improve your answering speed. You have only 75 seconds per math question in the real exam.
Track Weak Areas: Bookmark difficult problems and review your mistake history to continuously raise your score.
Part 3: Practical Questions & Solved Examples
Below is a preview of the type of questions asked by the UPSC. Test your current understanding of alloys composition NDA, metals nonmetals reactivity, GAT elements notes and review the step-by-step methods:
Use the interactive test panel below to solve live questions pulled directly from the SenaPrep exam bank.
Interactive Practice Quiz
Test your preparation live! Choose an option for each question to see instant feedback and deep step-by-step explanations.
Question 1 of 5 Live App Practice
The number of structural isomers of pentane is
Detailed Solution:
Correct Answer
✓ Option (d) is correct. Pentane has 3 structural isomers.
📖 Governing Law / Core Concept
Structural isomers are compounds with the same molecular formula but different structural arrangements.
🧪 Step-by-Step Breakdown
Pentan- C5H12 can be arranged structurally in three distinct isomers:
n-Pentane: A straight-chain form.
Isopentane (Methylbutane): A branched structure.
Neopentane: A more complex branched structure.
The illustrations of these isomers are as follows:
n-Pentane:
H H H H H
| | | | |
H - C - C - C - C - C - H
| | | | |
H H H H H
Isopentane:
H H H
| | |
H - C - C - C - H
| | |
H H H
|
H
Neopentane:
H H
| |
H - C - C - H
| |
H H
🔍 Option Analysis
Option A (5): Incorrect - More isomers than possible for pentane.
Option B (4): Incorrect - Incorrect count of branched forms.
Option C (2): Incorrect - Underestimation of the structural variations.
⚡ Mnemonic / Speed-Run
Remember: "Pentagon Has Three Structures" to signal the three isomers of pentane.
📊 Visual Suggestion
📊 Visual Suggestion
Create a comparative table of pentane isomers with visual representations for quick identification of each structural form.
📖 Factual Verification & Reference
📖 Factual Verification & Reference:
Verified against NCERT Class XII Chemistry, Chapter on Hydrocarbons.
Question 2 of 5 Live App Practice
Litmus, a well-known acid-base indicator, is derived from:
Detailed Solution:
Correct Answer
✓ Option B is correct. Litmus is derived from lichens.
📖 Governing Law / Core Concept
Litmus is a natural pH indicator obtained primarily from the lichen species Roccella tinctoria and Lecanora tartarea.
🧪 Step-by-Step Breakdown
Litmus undergoes color change upon reaction with acids and bases:
In acidic solutions (pH < 7): Litmus turns red.
In neutral solutions (pH = 7): Litmus remains purple.
In basic solutions (pH > 7): Litmus turns blue.
This color change occurs due to the protonation and deprotonation of the litmus dye, a complex mixture of various compounds providing these observable characteristics.
🔍 Option Analysis
A: Fungi - Incorrect; while lichens contain fungi, they are not derived solely from them.
C: Bacteria - Incorrect; litmus is not derived from bacterial sources.
D: Termite - Incorrect; termites do not produce litmus.
⚡ Mnemonic / Speed-Run
Remember: "Litmus Lichen - L for Lichen = Litmus!"
6. Visual Suggestion
6. Visual Suggestion
A pH scale diagram showing the color changes of litmus from red (in acidic) to blue (in basic) solutions, illustrating the transition points clearly for educational purposes.
📖 Factual Verification & Reference
📖 Factual Verification & Reference:
Verified against NCERT Class XI Chemistry, Chapter 14 (Environmental Chemistry).
Question 3 of 5 Live App Practice
What is the action of litmus on ethanol?
Detailed Solution:
Explanation: Ethanol is weak acid so it does not converts blue litmus to red, which indicate weak acidic nature of ethanol. So, ethanol is neutral towards litmus.
Question 4 of 5 Live App Practice
Which one of the following acid isused by goldsmith for cleaning of gold and silver articles ?
Detailed Solution:
Explanation: HNO₃ is used for cleaning of Gold and Silver Ornaments.
Question 5 of 5 Live App Practice
Which one of the following metals does NOT react with cold water to liberate hydrogen gas ?
Detailed Solution:
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