If you want to know how to study Chemical Kinetics and Nuclear Chemistry for JEE — Main or Advanced — this guide is built entirely from real previous-year papers. We pulled every question this chapter produced in the most recent cycles — 73 questions across JEE Main 2024, 2025 and 2026, plus 9 from JEE Advanced 2020–2026 — and sorted them by sub-topic. What follows is the real pattern behind a Physical Chemistry chapter that's growing on both exams at once.
Chemical Kinetics and Nuclear Chemistry carries a 5.68% weightage in JEE Main 2026, up 3.84% from 2025 — a modest but real gain that keeps it firmly in the high-frequency Physical Chemistry tier. On JEE Advanced it's climbing far more sharply, sitting at 5.88% weightage, up 87.86% year-on-year. Between the two exams, the signal is consistent even if the scale differs: this chapter is becoming more important, not less, and a huge share of that importance sits in one specific rate-law skill.
| Year | Questions (MCQ + Numerical) | Note |
|---|---|---|
| JEE Main 2024 | 20 | Lowest of the three years |
| JEE Main 2025 | 26 | Sharp rise from 2024 |
| JEE Main 2026 | 27 | 5.68% weightage, up 3.84% year-on-year |
ExamSIDE's archive shows 224 total JEE Main questions from this chapter since 2002, across 183 papers — an almost even split between MCQ and Numerical formats, unusual for a Physical Chemistry chapter and a sign that NTA tests both conceptual recall and numerical rate-constant calculations here in roughly equal measure. The steady climb from 20 (2024) to 26 (2025) to 27 (2026) questions, matched by rising weightage, makes this one of the more reliably-growing chapters in our series so far.
| Year | Questions | Note |
|---|---|---|
| 2020 | 2 | MCQ Multi + Numerical |
| 2021 | 1 | MCQ Multi only |
| 2022 | 1 | MCQ Single only |
| 2023 | 0 | No questions this year |
| 2024 | 2 | Numerical only (×2) |
| 2025 | 1 | Numerical only |
| 2026 | 2 | MCQ Single + MCQ Multi |
ExamSIDE's full archive (1978–2026) records 53 total JEE Advanced questions across 38 papers, with a large historical Subjective share (13) and a healthy split across MCQ-Single (15), MCQ-Multi (11) and Numerical (14) in the modern format. The chapter skipped only 2023 in our 2020–2026 window and otherwise shows up every year — and the 87.86% weightage jump into 2026 signals it's earning a bigger share of the paper, not just holding steady.
| Sub-topic | JEE Main (2024–26) | JEE Advanced (2020–26) | Combined |
|---|---|---|---|
| Integrated Rate Equations & Half-life | 32 | 3 | 35 |
| Rate Law & Order of Reaction | 9 | 4 | 13 |
| Arrhenius Equation & Activation Energy | 11 | 0 | 11 |
| Nuclear Chemistry & Radioactivity | 3 | 2 | 5 |
18 of the 73 JEE Main questions couldn't be confidently sub-topic-classified — about 25%, in line with several other Physical Chemistry chapters in this series, mostly questions built around tables of raw kinetic data (pressure vs. time, concentration vs. time) where the classifying keyword lives in a table our text extraction couldn't reliably parse. Where we found real signal, we used it.
Integrated Rate Equations & Half-life alone accounts for 35 of the 82 combined, categorised questions — 43%, comfortably the largest single sub-topic. This is the chapter's real center of gravity: first-order integrated rate law calculations (k = (1/t)ln([A]₀/[A])), half-life formulas, and reading rate constants off pressure-time or concentration-time data all fall under this one umbrella. Rate Law & Order of Reaction is the clear second priority, and notably makes up a larger share of Advanced questions (4 of 9, 44%) than Main ones (9 of 73, 12%) — Advanced leans harder into determining reaction order from experimental data than Main does.
Our Chemistry HOD, AN Naik Sir, builds Kinetics sessions around making k = (1/t)ln([A]₀/[A]) and its half-life shortcut completely automatic — because it alone explains more than four in ten PYQs here.
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"Most students can recite the first-order rate law formula but freeze the moment it's hidden inside a pressure-vs-time table. The exam almost never hands you concentration directly in this chapter — you have to extract it from total pressure or partial pressure data first. That translation step, not the formula itself, is what separates a five-second answer from a five-minute one." — AN Naik Sir, HOD Chemistry, JEE Prep Master
A large share of JEE Main 2024–2026 Numerical questions give you total system pressure at time t and at completion, rather than concentration directly — you must first convert pressure data into a concentration or fractional-conversion term before applying the integrated rate law. Skipping this translation step is the single most common reason otherwise-capable students stall on these questions.
Several 2024–2025 questions define two or three parallel or sequential first-order steps, each with its own activation energy, and ask for an overall or comparative rate constant (e.g., "if Ea for the second reaction is half of the first, and k₅₀₀ᴷ of the second equals double k₅₀₀ᴷ of the first, find k₃₀₀ᴷ of the second"). These require chaining the Arrhenius equation across two reactions in sequence, not just applying it once.
Multiple 2025–2026 Main questions present two statements about rate constants, half-life, or the Arrhenius equation and ask which is/are correct — testing conceptual precision (e.g., "the fraction of molecules with KE less than Ea" vs. the actual Boltzmann-factor definition) rather than numerical calculation.
Only 5 of 82 combined PYQs in our window are pure Nuclear Chemistry & Radioactivity (decay sequences, half-life dating, alpha/beta particle counting) — but they appear reliably in both exams (JEE Advanced 2024 and 2020 in our window; JEE Main scattered across all three years), meaning you can't skip this sub-topic even though it's clearly lower-priority by volume.
Advanced held at 1–2 questions per year across 2020–2026 with a gap in 2023 — the weightage jump into 2026 reflects a smaller overall paper (fewer total questions across all chapters) more than a flood of new Kinetics questions specifically. Don't over-read the percentage jump as "many more questions" — it's really "this chapter's existing question(s) now count for more."
The first-order integrated rate law is k = (1/t)ln([A]₀/[A]), and its half-life shortcut is t½ = 0.693/k — independent of initial concentration, which is the single most-tested conceptual fact about first-order reactions. For zero-order reactions, the integrated form is [A]₀ − [A] = kt and t½ = [A]₀/(2k), which does depend on initial concentration — mixing up which order's half-life is concentration-independent is one of the most common conceptual slips in this chapter. When a question gives pressure data instead of concentration, first write the stoichiometric relationship between total pressure and the extent of reaction, solve for the partial pressure of the reactant at time t, then substitute that in place of concentration in the rate law.
Worked example: A first-order decomposition A(g) → B(g) + C(g) starts with pure A at 1 bar in a 1 L vessel at temperature T. After 100 minutes, total pressure is 1.5 bar. Find the rate constant. Let x = drop in partial pressure of A. Since 1 mole of A gives 1 mole each of B and C, total pressure = (1−x) + x + x = 1+x. Setting 1+x = 1.5 gives x = 0.5, so partial pressure of A remaining = 1−0.5 = 0.5 bar. Using k = (1/t)ln(P₀/P) = (1/100)ln(1/0.5) = (1/100)ln2 = (1/100)(0.693) = 0.00693 min⁻¹. This exact "express total pressure in terms of x using stoichiometry, solve for remaining partial pressure, substitute into the standard rate law" sequence resolves the large majority of pressure-based Numerical questions in this chapter.
The rate law rate = k[A]ᵐ[B]ⁿ has orders m and n that must be determined experimentally — never assumed equal to stoichiometric coefficients unless the reaction is stated to be elementary. The standard method: compare two experimental runs where only one reactant's concentration changes, and use the ratio of rates to solve for that reactant's order directly. Advanced-style questions often go further, giving you the mechanism's slow (rate-determining) step and asking you to derive the rate law from it — in which case the rate law is written using only the species appearing in that slow step, with any intermediate species eliminated using the preceding fast equilibrium.
Worked example: For A + B → Products, when [A] is doubled at constant [B], rate doubles; when [B] is doubled at constant [A], rate becomes four times. Find the rate law. Since rate ∝ [A]¹ (doubling [A] doubles rate, so order in A = 1) and rate ∝ [B]² (doubling [B] quadruples rate, so order in B = 2), the rate law is rate = k[A][B]², giving an overall order of 3. This "isolate one variable at a time, compare the rate ratio to the concentration ratio, read off the exponent" method is the standard, reusable approach for every experimental rate-law determination question.
The Arrhenius equation k = Ae^(−Ea/RT) links rate constant, temperature and activation energy; its most exam-useful form is the two-temperature comparison ln(k₂/k₁) = −(Ea/R)(1/T₂ − 1/T₁), which lets you solve for Ea, a missing rate constant, or a missing temperature given the other three quantities. A catalyst works by lowering Ea (never by changing ΔH or the equilibrium position) — questions that ask you to compare catalysed vs. uncatalysed rates almost always reduce to plugging a modified (lower) Ea into this same two-point formula.
Worked example: A reaction's rate doubles when temperature rises from 298 K to 308 K. Find its activation energy. Using ln(k₂/k₁) = (Ea/R)(1/T₁ − 1/T₂) with k₂/k₁ = 2: ln2 = (Ea/8.314)(1/298 − 1/308). Computing 1/298 − 1/308 ≈ 0.003356 − 0.003247 = 0.000109 K⁻¹. So 0.693 = (Ea/8.314)(0.000109), giving Ea = 0.693 × 8.314 / 0.000109 ≈ 52,850 J/mol ≈ 52.85 kJ/mol. This two-temperature substitution is the single most-repeated calculation pattern in this sub-topic — the numbers change, the method never does.
Radioactive decay follows first-order kinetics, so the same k = (1/t)ln(N₀/N) and t½ = 0.693/k formulas from the Integrated Rate Equations sub-topic apply directly, just with N (number of nuclei) in place of concentration. For decay-series questions (alpha and beta particle counting), track mass number and atomic number separately: each alpha emission reduces mass number by 4 and atomic number by 2; each beta emission leaves mass number unchanged and increases atomic number by 1 — set up two simple equations (one for mass number, one for atomic number) and solve simultaneously for the number of each particle type emitted.
Worked example: A nucleus with mass number 238 and atomic number 92 decays through a series of alpha and beta emissions to a nucleus with mass number 206 and atomic number 82. Find the number of alpha and beta particles emitted. Let a = number of alpha particles, b = number of beta particles. Mass number equation: 238 − 4a = 206 → 4a = 32 → a = 8. Atomic number equation: 92 − 2a + b = 82 → 92 − 16 + b = 82 → b = 82 − 76 = 6. So 8 alpha and 6 beta particles are emitted. This two-equation, two-unknown setup handles essentially every decay-series counting question in this sub-topic.
It's a fast, formula-light sub-topic once you know the mass/atomic-number bookkeeping — AN Naik Sir makes sure it's never the reason you lose an easy mark.
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| Concept | Formula / Rule |
|---|---|
| First-order integrated rate law | k = (1/t)ln([A]₀/[A]) |
| First-order half-life | t½ = 0.693/k (independent of [A]₀) |
| Zero-order integrated rate law | [A]₀ − [A] = kt |
| Zero-order half-life | t½ = [A]₀/(2k) (depends on [A]₀) |
| Arrhenius equation | k = Ae^(−Ea/RT) |
| Two-temperature Arrhenius comparison | ln(k₂/k₁) = −(Ea/R)(1/T₂ − 1/T₁) |
| Radioactive decay (first-order analogue) | k = (1/t)ln(N₀/N), t½ = 0.693/k |
| Alpha/beta decay bookkeeping | Mass number: −4 per α; Atomic number: −2 per α, +1 per β |
The clearest shift is emphasis: Advanced leans more heavily into Rate Law & Order of Reaction (44% of its recent questions vs. just 12% for Main) and shows essentially no Arrhenius/activation-energy questions in our 2020–2026 window, unlike Main where Arrhenius accounts for 11 of 73 questions. If you're Advanced-focused, prioritise experimental rate-law determination and reversible-reaction kinetics (the 2026 Paper 1 question on forward/backward first-order rate constants is a good example of Advanced's taste for slightly more theoretical setups) over the Arrhenius-heavy drilling that pays off well on Main.
Against Definite Integration (technique-recognition-driven) and 3D Geometry (vector-projection-driven), Chemical Kinetics is closer to a data-translation chapter — the core formulas are few and simple, but a large share of questions bury the actual variable you need inside pressure tables, multi-step mechanisms, or decay sequences that must be unpacked first. Against Coordination Compounds and Aldehydes/Ketones (both concept-and-reaction-heavy Organic/Inorganic chapters), Kinetics is more numerically procedural, closer in spirit to Matrices and Determinants — reward comes from careful, repeatable execution of a small formula set rather than pattern-recognition across many reaction types.
Week 1 — Rate laws and order of reaction: Days 1–3: Rate law basics, differential vs. integrated forms, and the experimental method for determining order from concentration-rate data. Days 4–7: Zero-order and first-order integrated rate laws and their half-life formulas, with emphasis on which is concentration-independent.
Week 2 — Pressure-based and multi-step Numericals: Days 1–4: Converting total/partial pressure data into concentration terms using stoichiometry, then applying the standard rate law — this is the single highest-yield skill by volume. Days 5–7: Multi-step and sequential reaction problems involving two or more rate constants.
Week 3 — Arrhenius equation and activation energy: Days 1–4: The two-temperature Arrhenius comparison, catalyst-lowers-Ea questions, and reading Ea/frequency-factor off an Arrhenius plot. Days 5–7: Nuclear Chemistry & Radioactivity — decay kinetics and alpha/beta particle-counting bookkeeping.
Week 4 — Full drilling and Advanced-specific practice: Days 1–2: Statement-based (Assertion-Reason style) conceptual questions on rate constants, order and half-life. Days 3–5: Full timed sets from JEE Main 2024–2026. Days 6–7: JEE Advanced 2020–2026, with extra weight on experimental rate-law and reversible-reaction questions.
AN Naik Sir's sessions focus specifically on the pressure-to-concentration and mechanism-to-rate-law translation steps that cost students the most marks in this chapter.
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Every mistake above is one AN Naik Sir sees repeated every session, and corrects before it costs you marks on an actual paper.
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For anyone working out how to study Chemical Kinetics for JEE, weightage is the first signal — yes, at 5.68% weightage in 2026 (up 3.84% year-on-year), it's a steadily-growing Physical Chemistry chapter with 73 questions across just the last three years.
Based on our 2024–2026 analysis: 20 questions in 2024, 26 in 2025, and 27 in 2026 — a real, steady increase rather than a one-off spike.
Yes, and increasingly so — weightage jumped 87.86% into 2026, though raw question counts have stayed modest (1–2 per year) with a gap only in 2023.
Integrated rate equations and half-life — especially first-order kinetics and the pressure-to-concentration conversion step — account for 43% of all combined PYQs in this chapter, more than any other sub-topic.
Matrices rewards precise, error-free execution of known procedures with a fixed formula set. Chemical Kinetics has an even smaller formula set, but rewards correctly translating word-problem or table data (pressure, mechanism steps, decay series) into the right variable before you can even apply the formula.
Yes — mixing them up is one of the most common errors we found in this chapter's PYQ patterns, and the exam frequently tests exactly this distinction through statement-based conceptual questions.
Given its rising weightage on both exams, treat it as a top-priority Physical Chemistry chapter — a full 4 weeks if starting fresh, or 4–5 focused days for pure revision with extra time on pressure-based Numericals.
Yes — it's only 5 of 82 combined PYQs in our window, but it appears reliably across both exams and uses a small, learnable set of decay-bookkeeping rules, making it a low-effort, high-reliability sub-topic to lock down.
Chemical Kinetics and Nuclear Chemistry is a chapter with a small, learnable formula set where the real difficulty lies in extracting the right variable from pressure data, multi-step mechanisms, or decay sequences before you can apply it. This guide was built by pulling every JEE Main question from 2024–2026 and every JEE Advanced question from 2020–2026 directly from ExamSIDE's chapter-wise archives, classifying each by the technique it actually rewards, and cross-checking our counts against ExamSIDE's own published totals (224 JEE Main questions since 2002, 53 JEE Advanced questions since 1978). 18 of 73 JEE Main questions couldn't be confidently classified, mostly ones built around raw kinetic-data tables our text extraction couldn't fully parse — a gap we're flagging honestly rather than guessing past. If there's one takeaway on how to study Chemical Kinetics for JEE efficiently, it's this: master the first-order integrated rate law and the pressure-to-concentration translation step before anything else, since together they unlock the largest single share of this chapter's marks.
