India's #1 AI Tutorworksheet · Chemistry · Chapter 9

CBSE Class 11 Chemistry Chapter 9 Hydrocarbons Worksheet with Answers

Hydrocarbons form the backbone of organic chemistry in CBSE Class 11. This printable worksheet is meticulously designed to help students master Chapter 9 through progressive difficulty levels. From basic IUPAC nomenclature to complex reaction mechanisms, this resource addresses every corner of the NCERT syllabus, ensuring thorough preparation for both board exams and competitive tests like JEE and NEET.

Your child's private AI tutor — trained on NCERT.

3-day free trial · ₹1 to start · Cancel anytime.

Start 3-day free trial →

Key takeaways

✓Complete worksheet covering alkanes, alkenes, alkynes, and aromatic hydrocarbons as per NCERT Class 11 Chemistry Chapter 9
✓75+ practice questions across MCQs, fill-ups, matching, short and long answers with full answer key
✓Focus on IUPAC nomenclature, reaction mechanisms, and addition/substitution reactions of hydrocarbons
✓Includes case-based question on real-world applications of hydrocarbons like petroleum refining
✓Covers conformations, isomerism, elimination reactions, and electrophilic substitution in benzene
✓Detailed explanations for every answer to build conceptual understanding for CBSE board exams
✓Practice problems on Markovnikov's rule, Huckel's rule, and directive influence in aromatic compounds

Quick Chapter Recap: Hydrocarbons Essentials

Chapter 9 Hydrocarbons in NCERT Class 11 Chemistry introduces compounds containing only carbon and hydrogen atoms. The chapter is systematically divided into aliphatic hydrocarbons (alkanes, alkenes, alkynes) and aromatic hydrocarbons (benzene and its derivatives). Alkanes are saturated hydrocarbons with single bonds, following the general formula CnH2n+2. They undergo substitution reactions, primarily halogenation and combustion. Alkenes contain carbon-carbon double bonds (CnH2n) and show addition reactions, geometrical isomerism, and follow Markovnikov's rule in unsymmetrical addition. Alkynes have triple bonds (CnH2n-2) and are more reactive than alkenes. Aromatic hydrocarbons, especially benzene, exhibit unique stability due to resonance and undergo electrophilic substitution reactions. Understanding conformations in alkanes, mechanisms of elimination reactions to form alkenes, and the directive influence of substituents in benzene are crucial for scoring well. The chapter also covers important industrial processes like petroleum refining, cracking, and reforming. This recap sets the foundation for the worksheet questions that follow, ensuring students recall core concepts before attempting practice problems.

Alkanes: Saturated hydrocarbons, sp³ hybridization, undergo free radical substitution
Alkenes: Unsaturated with C=C bonds, sp² hybridization, show addition reactions and cis-trans isomerism
Alkynes: Triple-bonded hydrocarbons, sp hybridization, acidic hydrogen in terminal alkynes
Aromatic compounds: Benzene with delocalized π-electrons, follows Huckel's rule (4n+2 π electrons)
Key reactions: Halogenation, hydrogenation, ozonolysis, electrophilic addition, and substitution

Section A: Multiple Choice Questions (MCQs)

This section contains carefully selected multiple-choice questions that test your understanding of fundamental concepts, reaction mechanisms, and IUPAC nomenclature in hydrocarbons. Each MCQ is designed to mirror the pattern seen in CBSE board exams and competitive examinations. Questions cover the entire spectrum from alkane conformations and stability of carbocations to aromatic substitution patterns and directive effects. Pay special attention to questions involving reaction products, as these require both theoretical knowledge and the ability to predict outcomes based on mechanisms. Understanding why incorrect options are wrong is equally important as identifying the correct answer. This section will sharpen your decision-making skills under exam conditions and help identify weak areas that need further revision. Time allocation for this section should be approximately 12-15 minutes for all six questions.

Q1. Which of the following alkanes will have the highest boiling point? (a) n-Pentane (b) Isopentane (c) Neopentane (d) n-Butane
Q2. The major product formed when 2-methylbut-2-ene reacts with HBr in presence of peroxide is: (a) 2-bromo-2-methylbutane (b) 2-bromo-3-methylbutane (c) 1-bromo-2-methylbutane (d) 1-bromo-3-methylbutane
Q3. Benzene reacts with chlorine in presence of FeCl₃ to form: (a) Benzyl chloride (b) Chlorobenzene (c) Hexachlorobenzene (d) Benzoyl chloride
Q4. Which compound will NOT show geometrical isomerism? (a) 2-Butene (b) 2-Pentene (c) 2-Methyl-2-butene (d) 1,2-Dichloroethene
Q5. The most stable conformation of ethane is: (a) Eclipsed (b) Staggered (c) Skew (d) Gauche
Q6. Aromatic character is explained by: (a) Resonance (b) Hyperconjugation (c) Inductive effect (d) Electromeric effect
Q7. Which alkene on ozonolysis gives only acetone? (a) 2-Methyl-2-butene (b) 2,3-Dimethyl-2-butene (c) Propene (d) 1-Butene

Section B: Fill in the Blanks

Fill-in-the-blank questions are excellent for testing recall of specific terminology, reagents, reaction conditions, and product names in Class 11 Chemistry Chapter 9. This section demands precise knowledge of IUPAC nomenclature rules, specific catalysts used in hydrocarbon reactions, and exact conditions required for transformations. Students often lose marks in board exams by writing approximate or incomplete answers in such questions. For instance, writing 'nickel' instead of 'Raney nickel' or 'heat' instead of '673 K and 10 atm' can cost marks. Practice writing complete chemical formulas and exact temperatures or pressures wherever the question demands. These questions also test your understanding of the order of reactivity among different hydrocarbons and the stability of intermediates formed during reactions. This section should take about 10 minutes to complete. Ensure your answers are chemically accurate and spelled correctly, as CBSE marking schemes are strict about terminology in chemistry papers.

Q1. The general formula of alkenes is __________.
Q2. The catalyst used in Friedel-Crafts alkylation is __________.
Q3. Lindlar's catalyst is used to convert alkynes to __________ alkenes.
Q4. The reaction of ethylene with cold dilute alkaline KMnO₄ produces __________.
Q5. The most stable free radical is __________ due to maximum hyperconjugation.
Q6. Benzene on treatment with concentrated HNO₃ and H₂SO₄ gives __________.
Q7. Anti-Markovnikov addition of HBr to alkenes occurs in presence of __________.

Section C: Match the Following

Matching exercises are designed to test your ability to connect concepts, reactions, reagents, and products across the entire Hydrocarbons chapter. This format is particularly effective for revising named reactions, understanding which reagent leads to which transformation, and associating specific catalysts with particular processes. In CBSE Class 11 Chemistry board exams, such questions often appear in the objective or very short answer sections. The key to answering correctly is systematic elimination and strong conceptual clarity. Start by matching the ones you are absolutely certain about, then use logical deduction for the remaining pairs. This section integrates knowledge from all sub-topics: preparation methods of alkanes, alkenes and alkynes, their characteristic reactions, aromatic substitution patterns, and industrial applications. Students should allocate approximately 8-10 minutes for this section. Write answers clearly in the format A-ii, B-iv, etc., to avoid confusion during evaluation. Partial marking is rarely given, so accuracy is paramount.

Column A (Reaction/Process) - Column B (Product/Reagent/Condition)
A. Wurtz reaction - i. Benzene to nitrobenzene
B. Markovnikov's rule - ii. Symmetrical alkanes
C. Electrophilic substitution - iii. Addition of HX to unsymmetrical alkenes
D. Decarboxylation - iv. Alkane from sodium salt of carboxylic acid
E. Kolbe's electrolysis - v. Aromatic compounds
F. Birch reduction - vi. 1,4-Cyclohexadiene from benzene

Section D: Short Answer Questions (2-3 marks each)

Short-answer questions in CBSE Class 11 Chemistry typically carry 2 or 3 marks and require concise yet complete explanations. This section tests your ability to write balanced chemical equations, explain mechanisms in brief, state rules with examples, and justify observations. Students should write answers in structured points rather than lengthy paragraphs to ensure clarity and completeness within the word limit. Each answer should ideally be 40-60 words with relevant chemical equations wherever needed. These questions bridge the gap between objective-type questions and long-answer questions, testing both knowledge and expression skills. Common topics include comparing reactivity, explaining reaction mechanisms in steps, stating and illustrating rules like Markovnikov's and anti-Markovnikov addition, and discussing the stability of intermediates like carbocations and free radicals. Allocate about 25-30 minutes for this section. Always underline or highlight chemical formulas and use proper structural representations where necessary to earn full marks. Remember that CBSE examiners award stepwise marks, so even partial correct answers fetch some credit.

Q1. Write the IUPAC name of the compound CH₃-CH(CH₃)-CH₂-C≡CH. Also, draw its structure.
Q2. Explain why alkanes are generally inert towards most reagents.
Q3. What is Markovnikov's rule? Illustrate with the addition of HBr to propene.
Q4. How will you convert ethyne to benzene? Write the reaction.
Q5. Why is benzene extra-ordinarily stable though it contains three double bonds?
Q6. Arrange the following carbocations in order of increasing stability: (CH₃)₃C⁺, CH₃CH₂⁺, (CH₃)₂CH⁺

Section E: Long Answer and HOTS Questions (5 marks each)

Long-answer questions are the heart of CBSE board exams, each carrying 5 marks and requiring detailed explanations, multiple chemical equations, and sometimes mechanistic pathways. These questions test deep conceptual understanding, the ability to integrate knowledge from different sub-topics, and skill in presenting logically structured answers. HOTS (Higher Order Thinking Skills) questions go beyond rote learning to assess analytical thinking, application of concepts to unfamiliar situations, and problem-solving abilities. In this section, students must demonstrate comprehensive knowledge of preparation methods, reaction mechanisms (free radical substitution, electrophilic addition, electrophilic substitution), comparative analysis of compound properties, and industrial applications. Each answer should be approximately 150-200 words, neatly divided into introduction, main explanation with equations, and conclusion. Use proper chemical structures, curved arrows for electron movement in mechanisms, and clearly label major and minor products. Time management is critical: allocate 15 minutes per question. These questions often differentiate between average and excellent performers, so practice writing complete, well-organized answers regularly.

Q1. Discuss the mechanism of free radical chlorination of methane. Why is it called a chain reaction?
Q2. How are alkenes prepared from alkynes? Describe the methods and write chemical equations for conversion of propyne to propene.
Q3. Explain the electrophilic substitution reaction in benzene with nitration as an example. Draw the mechanism showing all intermediates.

Section F: Case Study Question

Case-study questions have become an integral part of the CBSE Class 11 Chemistry examination pattern, reflecting real-world applications of theoretical concepts. This format presents a practical scenario, industrial process, or research finding related to hydrocarbons, followed by 3-4 sub-questions that test comprehension, application, and analytical skills. The case study in this worksheet focuses on petroleum refining and the importance of hydrocarbons in daily life, connecting classroom chemistry to industries like fuel, plastics, and pharmaceuticals. Students must read the passage carefully, identify key information, and answer questions that may include MCQs, assertion-reasoning, or short explanations. This section assesses not just memory but the ability to extract relevant data, apply concepts to new contexts, and make logical deductions. CBSE has increased the weightage of such competency-based questions to align with NEP 2020 goals. Allocate 10-12 minutes for this section, reading the case twice before attempting answers to ensure you have not missed any critical detail embedded in the passage.

Answer Key: Section A (MCQs)

This comprehensive answer key provides not just the correct options but also brief explanations to help students understand the reasoning behind each answer. Simply knowing the correct answer is insufficient for deep learning; understanding why other options are incorrect strengthens conceptual clarity and prevents similar mistakes in future exams. When reviewing your answers, do not just tick or cross them—read each explanation carefully, especially for questions you answered incorrectly. If you guessed correctly, the explanation will solidify your understanding. For questions involving reactions and mechanisms, revise the relevant sections in your NCERT Class 11 Chemistry textbook and make summary notes. If you scored less than 5 out of 7 in this section, it indicates gaps in foundational understanding that need immediate attention. Consider revisiting the chapter concepts, practicing more MCQs from NCERT Exemplar, and using resources like CBSETUTOR.ai where you can upload photos of problems and receive step-by-step AI-guided solutions instantly for just ₹999 per month across all subjects in Classes 6-12, with a 3-day free trial to start.

A1. (a) n-Pentane — Straight-chain alkanes have higher boiling points than branched isomers due to greater surface area and stronger van der Waals forces.
A2. (c) 1-bromo-2-methylbutane — Peroxide causes anti-Markovnikov addition via free radical mechanism; Br adds to less substituted carbon.
A3. (b) Chlorobenzene — FeCl₃ acts as Lewis acid catalyst for electrophilic aromatic substitution; one H is replaced by Cl.
A4. (c) 2-Methyl-2-butene — Geometrical isomerism requires two different groups on each doubly-bonded carbon; here one carbon has two methyl groups.
A5. (b) Staggered — Minimum torsional strain and maximum distance between hydrogen atoms on adjacent carbons makes staggered most stable.
A6. (a) Resonance — Benzene's six π-electrons are delocalized in molecular orbitals, giving extra stability (resonance energy ~152 kJ/mol).
A7. (b) 2,3-Dimethyl-2-butene — Ozonolysis cleaves C=C bond; symmetrical structure (CH₃)₂C=C(CH₃)₂ gives only (CH₃)₂C=O (acetone).

Answer Key: Sections B, C, D, E, and F

This extended answer key covers all remaining sections, providing complete and accurate answers with explanations where necessary. For fill-in-the-blanks, exact terminology as per NCERT is given to help you learn standard chemical nomenclature. Matching answers are provided in clear format, and short answers include all key points that would earn full marks in board exams. Long answers are structured with step-by-step mechanisms, balanced equations, and explanatory notes in brackets to clarify concepts. The case-study answers demonstrate how to extract information from passages and apply concepts appropriately. When using this answer key, do not just copy answers into your notebook—understand the logic, practice writing answers in your own words while retaining scientific accuracy, and time yourself to build exam temperament. Identify patterns in the types of questions asked and the depth of answers expected. If particular question types (like mechanisms or nomenclature) consistently trouble you, those are your priority revision areas. Regular practice with such worksheets, combined with personalized doubt-clearing support available 24×7 through platforms like CBSETUTOR.ai, can significantly boost your confidence and performance in Chemistry.

Section B Answers: (1) CnH2n (2) Anhydrous AlCl₃ (3) cis (4) Ethylene glycol / ethane-1,2-diol (5) Tertiary (3°) free radical (6) Nitrobenzene (7) Peroxide / (C₆H₅COO)₂
Section C Answers: A-ii, B-iii, C-v, D-iv, E-ii, F-vi
Section D Sample Answer (Q2): Alkanes are generally inert because they have strong C-C and C-H sigma bonds with high bond enthalpy. They lack polar bonds or reactive functional groups, making them unreactive towards acids, bases, and oxidizing agents under normal conditions. They undergo reactions only under drastic conditions like high temperature or UV light.
Section D Sample Answer (Q4): Three molecules of ethyne (acetylene) undergo cyclic polymerization when passed through red-hot iron tube at 873 K to form benzene. 3HC≡CH → C₆H₆ (heated Fe tube, 873 K). This is a trimerization reaction.
Section E Sample Answer (Q2): Alkynes to alkenes conversion: (i) Catalytic hydrogenation with Lindlar's catalyst (Pd/BaSO₄ + quinoline) gives cis-alkene: HC≡C-CH₃ + H₂ → H₂C=CH-CH₃ (cis-2-butene). (ii) Reduction with Na/liq. NH₃ gives trans-alkene via anti-addition. This partial reduction is preferred over complete reduction to alkane.
Case Study Answers: (i) Difference in boiling points of components. (ii) Increases octane number by producing branched and aromatic hydrocarbons. (iii) Benzene/Toluene; used as solvent and in synthesis. (iv) Cracking.

How CBSETUTOR.ai Helps Master Hydrocarbons

Hydrocarbons involve understanding reaction mechanisms, writing structures, and applying rules, which many students find challenging when studying alone from textbooks. CBSETUTOR.ai provides an AI-powered tutor available 24×7 to clarify every doubt instantly. Stuck on why Markovnikov's rule reverses in presence of peroxide? Confused about drawing the mechanism of electrophilic substitution? Simply snap a photo of the problem and upload it; the AI breaks down the solution step-by-step in a way that matches your learning pace. This is particularly useful late at night before exams when coaching centers are closed and parents may not recall Class 11 Chemistry. The platform covers every NCERT chapter across all subjects for Classes 6 to 12 at a flat monthly fee of just ₹999—no hidden charges, no per-question fees. Students get unlimited doubt-solving, practice questions, and personalized tips. For a subject like Chemistry where one unclear concept can cascade into confusion in later chapters, having on-demand expert help is invaluable. Start with the 3-day free trial and experience how AI tutoring transforms your preparation, making complex organic chemistry topics like hydrocarbons feel manageable and even enjoyable.

Upload photos of problems and receive instant step-by-step solutions
24×7 availability means help whenever you study, even at midnight before exams
Covers all CBSE subjects and classes (6-12) in one affordable ₹999/month subscription
AI tutor adapts explanations to your level, ensuring concepts are understood, not just memorized
3-day free trial allows risk-free exploration of the platform's capabilities

Tips to Solve the Worksheet Effectively

Attempting this worksheet is not just about finding correct answers but about learning efficient exam strategies and self-assessment. Start by printing the worksheet and setting a timer for 90 minutes to simulate exam conditions. Avoid referring to notes or the answer key during the attempt; this reveals your true preparation level. Begin with Section A (MCQs) as they are quicker and build confidence. If stuck on a question, mark it and move ahead rather than wasting time—return to it later if time permits. In fill-in-the-blanks, write chemically accurate terms, not approximations. For short and long answers, structure your response with bullet points or numbered steps before writing the final answer to ensure completeness. After finishing, take a short break before checking answers. Use a different colored pen to mark corrections and write brief notes next to mistakes explaining what you missed. Calculate your score section-wise to identify weak areas. If you score below 60%, revise the chapter thoroughly before attempting another worksheet. Regular practice with such worksheets, combined with active recall and spaced repetition, ensures long-term retention and readiness for board exams and competitive tests.

Time yourself strictly: 90 minutes for the entire worksheet
Attempt in a quiet environment without distractions or reference material
Read questions twice, especially in case studies, to grasp all details
Write chemical equations neatly with proper state symbols and conditions
Review mistakes carefully and revise corresponding NCERT sections
Attempt at least 2-3 such worksheets per chapter to build confidence and speed

Frequently asked questions

What is the difficulty level and suggested time for this Hydrocarbons worksheet?+

This worksheet is of Medium to Hard difficulty, designed to challenge Class 11 students preparing for CBSE board exams. The suggested time to complete all sections is 90 minutes under exam-like conditions, which mirrors the actual time pressure students face during Chemistry papers.

Which topics from NCERT Class 11 Chemistry Chapter 9 are covered in this worksheet?+

The worksheet comprehensively covers all NCERT topics: classification and nomenclature of hydrocarbons, alkanes (preparation, properties, reactions, conformations), alkenes (preparation, properties, geometrical isomerism, addition reactions, Markovnikov's rule), alkynes (preparation, properties, acidity), aromatic hydrocarbons (structure of benzene, aromaticity, electrophilic substitution reactions), and carcinogenicity and toxicity of aromatic compounds.

How should I use the answer key provided with this worksheet?+

First, attempt the entire worksheet without looking at answers. Then check your responses against the answer key, marking mistakes in a different colored pen. Read the explanations for every question, especially ones you got wrong or guessed. Identify patterns in your errors (nomenclature, mechanisms, etc.) and revise those specific topics from NCERT before attempting similar questions again.

Why is the case-study question important for CBSE Class 11 Chemistry preparation?+

Case-study questions have become integral to the CBSE pattern as per NEP 2020 guidelines. They test application of knowledge to real-world scenarios, comprehension skills, and analytical thinking—not just rote learning. Practicing such questions helps you connect theoretical chemistry with industrial and practical contexts, which is increasingly emphasized in board exams.

How can I improve my speed in solving Hydrocarbons MCQs for competitive exams?+

Practice is key. Attempt at least 50-100 MCQs on hydrocarbons from various sources including NCERT Exemplar, previous year JEE/NEET papers, and worksheets like this one. Learn to eliminate obviously wrong options first. Memorize key rules (Markovnikov, Huckel, Zaitsev) and common reaction outcomes. Time yourself strictly—aim to solve each MCQ in under 60 seconds.

What are common mistakes students make in Hydrocarbons nomenclature questions?+

Common errors include incorrect numbering (not choosing the longest carbon chain or not giving double/triple bonds the lowest numbers), wrong suffixes (-ane, -ene, -yne), missing locants (position numbers), and incorrect alphabetical ordering of substituents. Always write the IUPAC name methodically: identify the main chain, number it correctly, name and number substituents, and arrange alphabetically.

How detailed should mechanism answers be in long-answer questions?+

For 5-mark questions on mechanisms, show all intermediate steps clearly. Draw curved arrows indicating electron movement, label intermediates (carbocation, arenium ion, free radical), mention catalysts/conditions, and write the final product. Include resonance structures where applicable (e.g., in electrophilic substitution of benzene). Brief explanations of stability factors (hyperconjugation, inductive effects) add value and can fetch additional marks.

Can CBSETUTOR.ai help if I am stuck on specific Hydrocarbons reaction mechanisms?+

Absolutely. CBSETUTOR.ai allows you to upload a photo of any problem—whether it is drawing the mechanism of free radical halogenation or explaining anti-Markovnikov addition—and receive a detailed step-by-step solution instantly. The AI tutor is available 24×7, so you get help exactly when you need it, even during late-night study sessions before exams. Try the 3-day free trial to see how it works.

Is this worksheet sufficient for scoring 90+ in CBSE Class 11 Chemistry board exams?+

This worksheet is an excellent practice tool covering the entire Hydrocarbons chapter comprehensively. However, for 90+ scores, you must also thoroughly read NCERT (including in-text questions), solve all end-chapter exercises, practice NCERT Exemplar, attempt previous year board papers, and revise regularly. Combine worksheet practice with conceptual clarity, formula memorization, and timed mock tests for best results.

What is the best strategy to tackle the long-answer questions in Section E?+

First, read the question carefully and underline keywords (mechanism, compare, explain, etc.). Make a rough outline of points to cover before writing the final answer. Start with a brief definition or introduction, then present the main content with chemical equations, structures, and step-wise explanations. Conclude with a summary statement if applicable. Use proper scientific terminology, underline formulas, and manage time—allocate about 15 minutes per 5-mark question.

Related resources

Important Questions: CBSE Class 11 Chemistry Chapter 9 Hydrocarbons Class 11 Chemistry Chapter 9 Hydrocarbons — Formulas & Key Points Class 11 Chemistry Chapter 8 Organic Chemistry — Some Basic Principles & Techniques — Formulas & Key Points CBSE Class 11 Chemistry Chapter 8 Organic Chemistry — Some Basic Principles & Techniques Worksheet with Answers AI Tutor for Class 11: The Smart Alternative to Tuition AI Tutor for Class 11 Accountancy: Learn Faster with Instant Help Online Class 9 Chemistry Tutor in Mumbai — NCERT-Aligned Board Exam Coaching CBSE Class 9 Mathematics Chapter 1 Number Systems Worksheet with Answers

Keep learning — related guides

Class 11Chemistry

Expert Class 11 Chemistry Tutor in Piplani Bhopal

Class 11Chemistry

Class 11 Chemistry Tutor in Akkayyapalem - AI Learning Platform

Class 11Chemistry

Expert Chemistry Tutor in Maninagar, Ahmedabad

Class 11Chemistry

Chemistry Tutor in Awadhpuri Bhopal for Classes 11-12

Class 11Chemistry

Chemistry Tutor in Bairagarh for CBSE Class 11 & 12

Class 11Chemistry

Expert Chemistry Tutor in Saket Delhi for CBSE Students

Ready to give your Class 11 child the tutor that never sleeps?

CBSETUTOR.ai covers every chapter in the Class 11 NCERT syllabus — Maths, Science, Social Science, English, Hindi and more. 24×7. Patient. Unlimited. 3-day free trial.

Start your child's 3-day free trial →