JEE · NEET · AIIMS · BITSAT · KVPY

Master Some Basic Concepts
of Chemistry
through Real Exam Questions

NCERT Class XI · Chapter 1 · Real PYQs from top competitive exams — filter by exam, attempt, and track your prep.

Attempt PYQs Study Strategy
IIT-JEE / JEE Main NEET AIIMS BITSAT KVPY
⚗️
—
Real PYQs
5
Exam Bodies
15+
Years Covered
~8%
Exam Weightage

PYQs Overview

⚖️
Mole Concept & Avogadro
Mole–mass–number interconversions — most frequently tested numerical topic in this chapter.
★★★★★
2001200820162021
🧮
Stoichiometry & Limiting Reagent
Balancing equations, mole ratios, limiting reactant, theoretical/actual yield calculations.
★★★★★
2003201020182022
📊
Empirical & Molecular Formula
Percentage composition, determination of empirical formula, vapour density method.
★★★★☆
200220092014
💧
Concentration Terms
Molarity, molality, normality, mole fraction, mass/volume % — both theory and numerical.
★★★★☆
200520132019
🔬
Laws of Chemical Combination
Lavoisier, Proust, Dalton, Gay-Lussac, Avogadro — statement, example and application MCQs.
★★★★☆
200020072015
🏷️
Atomic & Molecular Mass / IUPAC
Relative atomic mass, gram-atomic mass, formula/molecular mass, SI units, significant figures.
★★★☆☆
199920042017

Topic Frequency

Mole Concept & Avogadro's Number94%
Stoichiometry & Limiting Reagent90%
Concentration Terms (Molarity/Molality)82%
Empirical & Molecular Formula75%
Laws of Chemical Combination68%
Atomic & Molecular Mass55%
Significant Figures & SI Units40%
💡 Did You Know?
  • ✅ Avg. 1–2 questions per JEE Main paper
  • ✅ NEET asks 1–2 MCQs every year
  • ✅ Mole concept — zero skips in 15 yrs
  • ✅ Limiting reagent asked 8× since 2010
  • ✅ Numericals = ~70% of marks here

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Key Takeaways

🔑
1 mole = 6.022 × 10²³ particles

Avogadro's number is the bridge between atomic/molecular scale and lab-scale quantities. Non-negotiable.

⚡
Identify the limiting reagent first

Convert all reactants to moles → divide by stoichiometric coefficients → smallest quotient = limiting reagent.

📐
Empirical formula from % composition

% → moles (÷ atomic mass) → divide by smallest → round to whole numbers. Always check n = M/E.

🌊
Molarity changes with temperature; Molality doesn't

Molarity uses volume (varies with T); molality uses mass of solvent (constant). Key distinction for MCQs.

🧮
Five Laws of Chemical Combination

Conservation of Mass → Definite Proportions → Multiple Proportions → Reciprocal Proportions → Gay-Lussac's.

🎯
% Yield = (Actual / Theoretical) × 100

Always calculate theoretical yield from limiting reagent, never from excess. Common MCQ trap.

Study Strategy

1
Conceptual Foundation (Day 1–2)
Read NCERT text once; focus on laws of chemical combination, mole concept, and Dalton's atomic theory. Note every definition — NEET loves statement-based MCQs directly from NCERT.
2
Formula Sheet & Unit Conversions (Day 3)
Build a personal formula card: mole–mass–volume (STP), Avogadro conversions, molarity/molality formulae, % composition, empirical formula algorithm. Memorise SI units for all quantities.
3
Numericals Practice (Day 4–5)
Solve 25+ numericals: mole–mass interconversions, limiting reagent problems, solution concentration calculations, empirical/molecular formula determination. Time yourself for exam speed.
4
Attempt All PYQs Above (Day 6–7)
Go topic-wise through all questions. Mark sub-topics you get wrong — especially concentration term conversions and stoichiometry traps. These are your revision priorities for Day 8.
5
Rapid Revision Mock (Day 8)
Attempt a 30-question timed mock (Chapter 1 only) in 30 minutes. Review every wrong answer immediately. Repeat weekly until exam day to cement calculation speed.
🗓️ 8-Day Chapter Plan
DayFocus
1–2NCERT Reading + Laws + Notes
3Formula Sheet + SI Units
4–5Numericals (25+ per topic)
6–7All PYQs (this page)
8Full Mock + Error Analysis
🧠 Pro Tip: Chapter 1 is 70% numerical. If you master the mole concept thoroughly, limiting reagent and stoichiometry problems become trivial.
🚀

Ready to crack every Basic Concepts of Chemistry question?

Real PYQs, topic-wise overview, key takeaways and an 8-day strategy — all in one place.

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