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Class 12 Chemistry: questions from CBSE board papers, by chapter
Every question of the 4 CBSE board exam papers Shishya has solved (2026 Q.P. 56/1/1, 2025 Q.P. 56/1/1, 2024 Q.P. 56/1/1, 2023 Q.P. 56/1/1), listed under the NCERT chapter it was asked from. The question lines are in Shishya's own shorter words; each links to its step-by-step solution, and the paper page links CBSE's own question paper. Marks per chapter count every listed question, including both sides of an either/or choice.
Solutions
17 questions, 35 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q2 · 1 markAmong 0.1 M aqueous solutions of glucose, CaCl₂, KCl and urea, which freezes at the lowest temperature?
- Asked in CBSE 2026 · 56/1/1 · Q13 · 1 markAssertion: An azeotrope's components cannot be separated by fractional distillation. Reason: In an azeotrope, liquid and vapour have identical composition and it boils at a fixed temperature.
- Asked in CBSE 2026 · 56/1/1 · Q17 · 2 marksA phenol–aniline mixture: which deviation from Raoult's law does it show and why? How does its boiling point change on mixing?
- Asked in CBSE 2026 · 56/1/1 · Q24 · 3 marks0.61 g benzoic acid (M = 122 g mol⁻¹) in 5 g CS₂ dimerises 88%. CS₂ boils at 46.2 °C, Kb = 2.3 K kg mol⁻¹. Find the solution's boiling point.
- Asked in CBSE 2025 · 56/1/1 · Q1 · 1 markWhen solute particles associate in solution, how does the abnormal (observed) molar mass change?
- Asked in CBSE 2025 · 56/1/1 · Q12 · 1 markWhy does a raw mango kept in strong salt solution for pickling shrivel?
- Asked in CBSE 2025 · 56/1/1 · Q17(A) · 2 marks(a) Why does food cook faster in a pressure cooker than in an open pan? (b) Liquids X and Y on mixing give a smaller total volume. Which deviation from Raoult's law is this, and how does temperature change on mixing?
- Asked in CBSE 2025 · 56/1/1 · Q17(B) · 2 marksWhat is an azeotrope? Which kind arises from negative deviation from Raoult's law? Give one example.
- Asked in CBSE 2025 · 56/1/1 · Q22 · 3 marksAn aqueous glucose solution (M = 180 g/mol) boils at 100.20 °C. Find its freezing point. Kf = 1.86 and Kb = 0.512 K kg mol⁻¹.
- Asked in CBSE 2024 · 56/1/1 · Q4 · 1 markWhat can be said about the van't Hoff factor i of an electrolyte that associates in a solvent?
- Asked in CBSE 2024 · 56/1/1 · Q13 · 1 markAssertion: adding NaCl to water lowers its freezing point. Reason: NaCl dissociates in water. Choose the A-R code.
- Asked in CBSE 2024 · 56/1/1 · Q31(a) · 5 marks(i) CO₂ dissolves in water more than O₂ at one temperature; which has the larger KH and why? (ii) What happens to blood cells in aqueous NaCl stronger than 0.9% (mass/volume)? (iii) A 1 molal aqueous solution of A₂B₃ is 60% ionised; find its boiling point. Kb(water) = 0.52 K kg mol⁻¹.
- Asked in CBSE 2024 · 56/1/1 · Q31(b) · 5 marks(i) At 25 °C p°A = 75 mm Hg and p°B = 25 mm Hg; liquid mixture has xA = 0.4. Find the mole fraction of B in the vapour. (ii) Define a colligative property; which one is preferred for molar masses of macromolecules? (iii) Why are equimolar NaCl and glucose solutions not isotonic?
- Asked in CBSE 2023 · 56/1/1 · Q1 · 1 markWhich colligative property is preferred for finding molar masses of polymers and proteins?
- Asked in CBSE 2023 · 56/1/1 · Q2 · 1 markWhy do people at high altitudes have a low oxygen level in blood and tissues?
- Asked in CBSE 2023 · 56/1/1 · Q19 · 2 marksState Henry's law and give one use of it.
- Asked in CBSE 2023 · 56/1/1 · Q26 · 3 marks(a) Give a difference between ideal and non-ideal solutions. (b) Urea (30 g) is dissolved in water (846 g). Pure water has vapour pressure 23.8 mm Hg at 298 K; find the vapour pressure of water over this solution.
Electrochemistry
21 questions, 58 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q5 · 1 markAqueous CuCl₂ is electrolysed with platinum electrodes. What happens?
- Asked in CBSE 2026 · 56/1/1 · Q23(a) · 3 marks(i) Why is Kc linked to E°cell rather than Ecell? (ii) Metals A and B have E° = −0.24 V and +0.80 V. Which one releases H₂ from dilute H₂SO₄? (iii) Give the cell reaction of a lead storage battery while it is being charged.
- Asked in CBSE 2026 · 56/1/1 · Q23(b) · 3 marksWhat kind of battery is the mercury cell, what advantage does it have over a dry cell, and what is its overall reaction?
- Asked in CBSE 2026 · 56/1/1 · Q33(a) · 5 marksA cell at 298 K has a Mg anode dipping in 0.01 M Mg²⁺ and an Ag cathode dipping in 0.001 M Ag⁺. Standard potentials: Ag⁺/Ag +0.80 V, Mg²⁺/Mg −2.37 V. Take F = 96500 C mol⁻¹ and log 10 = 1. Find emf and ΔG.
- Asked in CBSE 2026 · 56/1/1 · Q33(b) · 5 marksCell reaction: 2AgCl(s) + H₂ (at 0.4 atm) gives 2Ag(s) with H⁺ at 0.1 M and Cl⁻ at 0.2 M (2 mol of each ion). ΔG° = −43500 J mol⁻¹. Find the emf at 25 °C, taking F = 96500 C mol⁻¹ and log 10 = 1.
- Asked in CBSE 2025 · 56/1/1 · Q2 · 1 markE° of Sn⁴⁺/Sn²⁺ is +0.15 V and of Cr³⁺/Cr is −0.74 V. Find E°cell when the two standard couples form a cell.
- Asked in CBSE 2025 · 56/1/1 · Q23 · 3 marks(a) State (i) Kohlrausch's law of independent migration of ions, (ii) Faraday's first law of electrolysis. (b) E°(X²⁺/X) = −2.36 V, E°(Y²⁺/Y) = −0.14 V, E°(Fe²⁺/Fe) = −0.44 V. Which metal, X or Y, is better for coating iron against corrosion, and why?
- Asked in CBSE 2025 · 56/1/1 · Q31(A) · 5 marks(a) For Sn | Sn²⁺ (0.004 M) || H⁺ (0.02 M) | H₂ (1 bar) | Pt at 298 K, write the cell reaction and find the emf. E°(Sn²⁺/Sn) = −0.14 V, E°(H⁺/H₂) = 0.00 V. (b) Explain: (i) electrolysis of aqueous NaCl gives Cl₂, not O₂, at the anode although E° values favour O₂; (ii) conductivity of CH₃COOH falls on dilution.
- Asked in CBSE 2025 · 56/1/1 · Q31(B) · 5 marks(a) Give the anode, cathode and overall reactions of a lead storage battery while discharging. (b) Half-cell: Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2Cr³⁺ + 7H₂O, E° = 1.33 V. Find its potential with 0.01 M K₂Cr₂O₇, 0.01 M Cr³⁺ and 1.0 × 10⁻⁴ M H⁺. log 10 = 1.
- Asked in CBSE 2024 · 56/1/1 · Q17 · 2 marksFind the electrode potential of Fe²⁺(0.01 M)/Fe at 298 K. E°(Fe²⁺/Fe) = −0.45 V, log 10 = 1.
- Asked in CBSE 2024 · 56/1/1 · Q22 · 3 marksA cell shows 100 Ω with 0.05 M KCl (κ = 1.35 × 10⁻² Ω⁻¹ cm⁻¹) and 90 Ω with 0.02 M AgNO₃ at 25 °C. Find κ and Λm of the AgNO₃ solution.
- Asked in CBSE 2024 · 56/1/1 · Q29(a) · 1 markCase on batteries and fuel cells: how is a primary battery different from a secondary one?
- Asked in CBSE 2024 · 56/1/1 · Q29(b) · 1 markWhy does the mercury cell keep a steady potential of 1.35 V throughout its life?
- Asked in CBSE 2024 · 56/1/1 · Q29(c) · 2 marksGive the reactions taking place when a lead storage battery is recharged.
- Asked in CBSE 2024 · 56/1/1 · Q29(c)-OR · 2 marksState two advantages that fuel cells have over other galvanic cells.
- Asked in CBSE 2023 · 56/1/1 · Q3 · 1 markWhich cell notation correctly represents Zn + 2Ag⁺ → Zn²⁺ + 2Ag?
- Asked in CBSE 2023 · 56/1/1 · Q4 · 1 markFor a spontaneous cell reaction, what are the signs of ΔG and E°cell?
- Asked in CBSE 2023 · 56/1/1 · Q20(a) · 2 marksOn dilution, Λm of electrolyte A rises 25 times and that of B rises 1.5 times. Which is the strong electrolyte? Support with a graph.
- Asked in CBSE 2023 · 56/1/1 · Q20(b) · 2 marksNaOH solution (0.05 mol L⁻¹) fills a tube 50 cm long and 1 cm in diameter; its resistance is 5.55 × 10³ Ω. Find the conductivity κ.
- Asked in CBSE 2023 · 56/1/1 · Q33(a) · 5 marks(i) State Kohlrausch's law and write Λ°m for acetic acid using it. (ii) For Ni(s) + 2Ag⁺(aq) ⇌ Ni²⁺(aq) + 2Ag(s) at 298 K, find the maximum work and log Kc, using standard potentials −0.25 V for Ni²⁺/Ni and +0.80 V for Ag⁺/Ag (F = 96500 C mol⁻¹).
- Asked in CBSE 2023 · 56/1/1 · Q33(b) · 5 marks(i) State Faraday's first law of electrolysis; how many faradays reduce 1 mol Cu²⁺ to Cu? (ii) Find the emf at 298 K of Mg(s) | Mg²⁺(0.1 M) || Cu²⁺(0.01 M) | Cu(s); standard emf is +2.71 V (F = 96500 C mol⁻¹; take log 10 = 1).
Chemical Kinetics
20 questions, 31 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q1 · 1 markFour graphs are shown; pick the one that fits a first order reaction.
- Asked in CBSE 2026 · 56/1/1 · Q4 · 1 markWhich expression gives the fraction of molecules having energy at least Ea?
- Asked in CBSE 2026 · 56/1/1 · Q21 · 2 marksThe elementary (one-step) reaction 2A + B → 2C: how does the rate change when the vessel volume is cut to one-third? Does the order change?
- Asked in CBSE 2026 · 56/1/1 · Q22 · 3 marksFirst order gas reaction C₂H₅Cl(g) → C₂H₄(g) + HCl(g): total pressure is 0.30 atm at t = 0 s and 0.50 atm at t = 30 s. Find k. (log 3 = 0.48)
- Asked in CBSE 2025 · 56/1/1 · Q24 · 3 marksA first order reaction is half done in 20 min at 300 K and in 5 min at 350 K. Find Ea. R = 8.314 J K⁻¹ mol⁻¹, log 4 = 0.602.
- Asked in CBSE 2025 · 56/1/1 · Q29(a) · 2 marksCase on reaction rate, order and molecularity. (i) What is the rate determining step? (ii) What is a complex reaction?
- Asked in CBSE 2025 · 56/1/1 · Q29(b) · 1 markHow does temperature affect a reaction's rate constant?
- Asked in CBSE 2025 · 56/1/1 · Q29(b)-OR · 1 markWhy does molecularity apply only to elementary reactions while order applies to both elementary and complex ones?
- Asked in CBSE 2025 · 56/1/1 · Q29(c) · 1 markX → Y is second order. How does the rate of forming Y change if [X] is made 3 times?
- Asked in CBSE 2024 · 56/1/1 · Q5 · 1 markWrite the differential rate expression linking d[Y]/dt and d[P]/dt for X + 2Y → P.
- Asked in CBSE 2024 · 56/1/1 · Q9 · 1 markFor a plot of log k versus 1/T (Arrhenius equation), state the slope and the intercept.
- Asked in CBSE 2024 · 56/1/1 · Q18 · 2 marksWhat is molecularity? Give one condition under which a bimolecular reaction behaves as first order.
- Asked in CBSE 2024 · 56/1/1 · Q23 · 3 marksFor 2NO + Br₂ → 2NOBr: [NO], [Br₂] (mol/L) and initial rate (mol L⁻¹ s⁻¹) are 0.05, 0.05, 1.0 × 10⁻³; 0.05, 0.15, 3.0 × 10⁻³; 0.15, 0.05, 9.0 × 10⁻³. Find (a) the orders in NO and Br₂, (b) k, (c) the rate at [NO] = 0.4 M, [Br₂] = 0.2 M.
- Asked in CBSE 2023 · 56/1/1 · Q5 · 1 markAmong ΔH, ΔG, Ea and ΔS, which quantity does a catalyst change?
- Asked in CBSE 2023 · 56/1/1 · Q6 · 1 markWhat is the order of the photochemical reaction H₂(g) + Cl₂(g) → 2HCl(g) (in light, hν)?
- Asked in CBSE 2023 · 56/1/1 · Q17 · 1 markAssertion: H₂ + Br₂ → 2HBr seems to have molecularity 2. Reason: in this elementary step two reactant molecules take part.
- Asked in CBSE 2023 · 56/1/1 · Q31(i) · 1 markDefine the average rate of a reaction.
- Asked in CBSE 2023 · 56/1/1 · Q31(ii) · 1 markName two factors on which reaction rate depends.
- Asked in CBSE 2023 · 56/1/1 · Q31(iii) · 2 marksFor a zero order reaction: (1) how does the rate depend on concentration? (2) what is the unit of k?
- Asked in CBSE 2023 · 56/1/1 · Q31(iii)-OR · 2 marks(1) Reaction P + 2Q → products follows rate = k[P]^(1/2)[Q]. Give the overall order. (2) Define a pseudo first order reaction with an example.
The d-and f-Block Elements
15 questions, 39 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q3 · 1 markWhich one is not a transition metal: Sc, Ag, Hg or Cu?
- Asked in CBSE 2026 · 56/1/1 · Q15 · 1 markAssertion: Actinoids show many different oxidation states. Reason: Actinoids are radioactive.
- Asked in CBSE 2026 · 56/1/1 · Q32(a) · 5 marks(i) E°(M²⁺/M) in V: V −1.18, Cr −0.91, Mn −1.18, Fe −0.44, Co −0.28, Ni −0.25, Cu +0.34. (I) Why is the trend irregular? (II) Why is Cu's value unusually positive? (III) Why is Mn's value so negative? (3 marks) (ii) Ionic equations for KMnO₄ oxidising I⁻ in acidic and in alkaline solution. (2 marks)
- Asked in CBSE 2026 · 56/1/1 · Q32(b) · 5 marks(i) Name a lanthanoid that shows (I) +4 and (II) +2 oxidation state. (1 mark) (ii) Why are transition metals good catalysts? (1) (iii) Why does Cr melt higher than Mn? (1) (iv) What happens to acidified KMnO₄ solution left standing for some time? Equation and type of reaction. (2)
- Asked in CBSE 2025 · 56/1/1 · Q3 · 1 markSpin-only magnetic moment of Cr³⁺ (Cr: Z = 24)?
- Asked in CBSE 2025 · 56/1/1 · Q4 · 1 markTo what does acidified KMnO₄ oxidise sulphite ion?
- Asked in CBSE 2025 · 56/1/1 · Q18 · 2 marksComplete and balance: (a) 2MnO₄⁻ + 10I⁻ + 16H⁺ → ? (b) Cr₂O₇²⁻ + 6Fe²⁺ + 14H⁺ → ?
- Asked in CBSE 2025 · 56/1/1 · Q25 · 3 marksFor the 3d series Sc to Zn: (a) why is E°(Cu²⁺/Cu) unusually positive? (b) which element is a strong reducing agent in the +2 state, and why? (c) why are Zn²⁺ salts colourless?
- Asked in CBSE 2024 · 56/1/1 · Q1 · 1 markAmong Fe (Z = 26), Mn (Z = 25), Cr (Z = 24) and V (Z = 23), which should have the highest third ionisation enthalpy?
- Asked in CBSE 2024 · 56/1/1 · Q14 · 1 markAssertion: Zr and Hf are hard to separate. Reason: lanthanoid contraction makes their radii almost equal. Choose the A-R code.
- Asked in CBSE 2024 · 56/1/1 · Q33(a) · 5 marks(i) Explain: (1) Zn, Cd, Hg have low melting and boiling points; (2) among d⁴ ions Cr²⁺ is a strong reductant but Mn³⁺ a strong oxidant; (3) E°(Cu²⁺/Cu) is positive (+0.34 V). (ii) Finish and balance: (1) KMnO₄ on heating; (2) Cr₂O₇²⁻ + 6I⁻ + 14H⁺ →.
- Asked in CBSE 2024 · 56/1/1 · Q33(b) · 5 marks(i) Which is more stable in water, Cu₂Cl₂ or CuCl₂, and why? (ii) Outer configuration common to all f-block elements. (iii) Which of Sc³⁺, Fe³⁺, Zn²⁺ (Z = 21, 26, 30) is coloured in water, and why? (iv) How is K₂Cr₂O₇ made from sodium chromate? (v) Why are transition metals and their compounds good catalysts?
- Asked in CBSE 2023 · 56/1/1 · Q7 · 1 markWhich oxidation state is the most common and stable one for lanthanoids?
- Asked in CBSE 2023 · 56/1/1 · Q21 · 2 marksComplete: (a) 2MnO₄⁻ + 5NO₂⁻ + 6H⁺ → ; (b) Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → .
- Asked in CBSE 2023 · 56/1/1 · Q34 · 5 marksGive reasons: (i) Mn reaches +7, the highest oxidation state in the 3d series; (ii) transition metals and their compounds are good catalysts; (iii) Cr²⁺ (d⁴) is a reductant but Mn³⁺ (d⁴) is an oxidant; (iv) Zn has the lowest enthalpy of atomisation; (v) Cu⁺ is unstable in water.
Coordination Compounds
22 questions, 39 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q7 · 1 markWhat is the secondary valency of cobalt in [Co(NH₃)₅(NO₂)]²⁺?
- Asked in CBSE 2026 · 56/1/1 · Q19(a) · 2 marksGive IUPAC names: (i) [Ag(NH₃)₂][Ag(CN)₂] (ii) K₃[Fe(C₂O₄)₃].
- Asked in CBSE 2026 · 56/1/1 · Q19(b) · 2 marks(i) Suggest a chemical test proving [Co(NH₃)₅SO₄]Cl and [Co(NH₃)₅Cl]SO₄ are ionisation isomers. (ii) Explain the chelate effect with one example.
- Asked in CBSE 2026 · 56/1/1 · Q30(a) · 2 marksIn an octahedral crystal field, which d-orbitals rise in energy as ligands approach, and why?
- Asked in CBSE 2026 · 56/1/1 · Q30(b) · 1 markBy crystal field theory, give the d-electron configuration of the metal ion in (i) [CoF₆]³⁻ (ii) [Co(NH₃)₆]³⁺. (Co = 27)
- Asked in CBSE 2026 · 56/1/1 · Q30(c) · 1 markBoth tetrahedral, yet [NiCl₄]²⁻ is paramagnetic and [Ni(CO)₄] diamagnetic. Explain. (Ni = 28)
- Asked in CBSE 2026 · 56/1/1 · Q30(c)-OR · 1 markGive the hybridisation and magnetic nature of [Fe(CN)₆]³⁻. (Fe = 26)
- Asked in CBSE 2025 · 56/1/1 · Q5 · 1 markGive the IUPAC name of [Pt(NH₃)₂Cl₂]²⁺.
- Asked in CBSE 2025 · 56/1/1 · Q13 · 1 markA: [Cr(H₂O)₆]Cl₂ and [Fe(H₂O)₆]Cl₂ are homoleptic. R: every ligand on the metal is the same.
- Asked in CBSE 2025 · 56/1/1 · Q32(A) · 5 marks(a) Why are low-spin tetrahedral complexes not known? (b) Why is Co²⁺ (Z = 27) readily oxidised to Co³⁺ with a strong ligand? (c) Which isomerism does [Co(NH₃)₆][Cr(CN)₆] show? (d) Why is [Ni(H₂O)₆]²⁺ green but [Ni(CN)₄]²⁻ colourless (Ni: Z = 28)? (e) IUPAC name of [Co(NH₃)₅(CO₃)]Cl.
- Asked in CBSE 2025 · 56/1/1 · Q32(B) · 5 marks(a) What is the chelate effect? Give an example. (b) Hybridisation and magnetic nature of [Fe(CN)₆]⁴⁻ (Fe: Z = 26)? (c) PtCl₂·2NH₃ gives no reaction with AgNO₃. Write its formula.
- Asked in CBSE 2024 · 56/1/1 · Q24 · 3 marks(a) Formula of potassium tetrahydroxidozincate(II). (b) Put [Cr(NH₃)₅Cl]Cl₂, [Cr(NH₃)₃Cl₃], [Cr(NH₃)₆]Cl₃ in increasing order of solution conductivity. (c) Name the isomerism shown by (i) [Co(NH₃)₅NO₂]²⁺ and (ii) [Co(en)₃]Cl₃.
- Asked in CBSE 2024 · 56/1/1 · Q30(a) · 1 markCase on VBT and crystal field theory: define crystal field splitting energy.
- Asked in CBSE 2024 · 56/1/1 · Q30(b) · 1 markUsing crystal field theory, explain why [Ti(H₂O)₆]³⁺ is violet.
- Asked in CBSE 2024 · 56/1/1 · Q30(c) · 2 marksWhy is [Cr(NH₃)₆]³⁺ paramagnetic but [Ni(CN)₄]²⁻ diamagnetic? (Cr = 24, Ni = 28)
- Asked in CBSE 2024 · 56/1/1 · Q30(c)-OR · 2 marksWhy is [Fe(CN)₆]³⁻ an inner orbital complex while [Fe(H₂O)₆]³⁺ is outer orbital? (Fe = 26)
- Asked in CBSE 2023 · 56/1/1 · Q8 · 1 markWhat type of isomerism is shown by the pair [Co(SO₄)(NH₃)₅]Br and [Co(Br)(NH₃)₅]SO₄?
- Asked in CBSE 2023 · 56/1/1 · Q18 · 1 markAssertion: low-spin tetrahedral complexes are rare. Reason: for tetrahedral complexes Δt is smaller than the pairing energy.
- Asked in CBSE 2023 · 56/1/1 · Q32(i) · 1 markPtCl₂·2NH₃ gives no precipitate with AgNO₃. Write its formula.
- Asked in CBSE 2023 · 56/1/1 · Q32(ii) · 1 markSecondary valency of cobalt in [Co(en)₃]³⁺?
- Asked in CBSE 2023 · 56/1/1 · Q32(iii) · 2 marks(1) Formula of iron(III) hexacyanidoferrate(II). (2) IUPAC name of [Co(NH₃)₅Cl]Cl₂.
- Asked in CBSE 2023 · 56/1/1 · Q32(iii)-OR · 2 marksHybridisation and magnetic nature of [Ni(CN)₄]²⁻ (Ni: Z = 28).
Haloalkanes and Haloarenes
15 questions, 29 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q9 · 1 markWhich statement about enantiomers is false: same chemical reactivity, same specific rotation, same melting/boiling point, or same refractive index?
- Asked in CBSE 2026 · 56/1/1 · Q18 · 2 marksGive two reasons why haloarenes react poorly in nucleophilic substitution.
- Asked in CBSE 2026 · 56/1/1 · Q28 · 3 marksX (C₄H₉Br) gives an alcohol with aqueous KOH at a rate depending only on [X]. Y, an optically active isomer of X, reacts with aqueous KOH at a rate depending on both [Y] and [KOH]. (a) Structures of X and Y. (b) Which racemises and why? (c) Which gives inversion of configuration and why?
- Asked in CBSE 2025 · 56/1/1 · Q6 · 1 markOrder by increasing boiling point: (i) (CH₃)₂CHCH₂Br, (ii) CH₃CH₂CH₂CH₂Br, (iii) (CH₃)₃CBr.
- Asked in CBSE 2025 · 56/1/1 · Q7 · 1 markWhat happens to configuration when an alkyl halide reacts by the SN2 path?
- Asked in CBSE 2025 · 56/1/1 · Q14 · 1 markA: boiling points fall as RI > RBr > RCl > RF. R: alkyl chlorides, bromides and iodides boil much higher than hydrocarbons of similar molar mass.
- Asked in CBSE 2025 · 56/1/1 · Q26(A) · 3 marksGive the main monohalogen product: (a) 4-chloroethylbenzene (Cl–C₆H₄–CH₂CH₃, para) with Br₂ and heat; (b) 1-methylcyclohexene + HBr; (c) 4-(hydroxymethyl)phenol (HOCH₂–C₆H₄–OH, para) with HCl and heat.
- Asked in CBSE 2025 · 56/1/1 · Q26(B) · 3 marksConvert: (a) chlorobenzene → biphenyl; (b) propene → 1-iodopropane; (c) 2-bromobutane → but-2-ene.
- Asked in CBSE 2024 · 56/1/1 · Q6 · 1 markWhich of the four bromides drawn in the paper reacts fastest by the SN1 path?
- Asked in CBSE 2024 · 56/1/1 · Q20(a) · 2 marksGive the main monohalo product: (i) C₆H₅CH=CH₂ + HBr; (ii) cyclohexene + Br₂ in UV light.
- Asked in CBSE 2024 · 56/1/1 · Q20(b) · 2 marksExplain: (i) a Grignard reagent must be made in dry conditions; (ii) aqueous KOH turns alkyl halides into alcohols but alcoholic KOH gives alkenes.
- Asked in CBSE 2024 · 56/1/1 · Q25 · 3 marks(a) Which is allylic: CH₃–CH=CH–Br or CH₂=CH–CH(Br)–CH₃? (b) Which is more reactive to nucleophilic substitution, chlorobenzene or 2,4,6-trinitrochlorobenzene, and why? (c) Which C₄H₉Cl isomer boils lowest?
- Asked in CBSE 2023 · 56/1/1 · Q9 · 1 markWhich method is best for making alkyl fluorides?
- Asked in CBSE 2023 · 56/1/1 · Q22 · 2 marksIdentify A and B: (a) CH₃CH(OH)CH₃ with PCl₅ gives A, which with AgCN gives B; (b) CH₃CH₂CH₂Cl with KOH in ethanol gives A, which with HBr gives B.
- Asked in CBSE 2023 · 56/1/1 · Q27 · 3 marksMain product: (a) CH₃Cl with NaI in acetone; (b) hydrolysis of 2,4,6-trinitrochlorobenzene; (c) n-butyl chloride with alcoholic KOH.
Alcohols, Phenols and Ethers
18 questions, 27 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q6 · 1 markAcetylating which compound gives aspirin?
- Asked in CBSE 2026 · 56/1/1 · Q8 · 1 markWhat does phenol give with dilute HNO₃ at low temperature?
- Asked in CBSE 2026 · 56/1/1 · Q14 · 1 markAssertion: The –OH group of phenol sends incoming groups to the meta position. Reason: –OH activates the benzene ring for electrophilic substitution.
- Asked in CBSE 2026 · 56/1/1 · Q27 · 3 marksGive the equations for Kolbe's reaction, the Reimer–Tiemann reaction (both on phenol) and Friedel–Crafts acylation of anisole.
- Asked in CBSE 2025 · 56/1/1 · Q8 · 1 markCorrect order of acid strength among C₆H₅OH, H₂O and ROH?
- Asked in CBSE 2025 · 56/1/1 · Q15 · 1 markA: ethanol boils higher than methoxymethane. R: ethanol shows intramolecular H-bonding.
- Asked in CBSE 2025 · 56/1/1 · Q30(a) · 2 marksCase on electrophilic substitution of phenols and the Reimer-Tiemann reaction. What forms when phenol reacts with (i) Br₂ in CS₂, (ii) concentrated HNO₃?
- Asked in CBSE 2025 · 56/1/1 · Q30(b) · 1 markWhy is phenol not easily protonated?
- Asked in CBSE 2025 · 56/1/1 · Q30(c) · 1 markWhich is the stronger acid, phenol or cresol? Why?
- Asked in CBSE 2025 · 56/1/1 · Q30(c)-OR · 1 markGive the IUPAC name of the product of the Reimer-Tiemann reaction of phenol.
- Asked in CBSE 2024 · 56/1/1 · Q2 · 1 markWhich alcohol gives a ketone when oxidised by CrO₃: (CH₃)₂CHCH₂OH, CH₃CH₂CH₂OH, (CH₃)₃COH or CH₃CH₂CH(OH)CH₃?
- Asked in CBSE 2024 · 56/1/1 · Q10 · 1 markName the reaction in which an alkyl halide and a sodium alkoxide give an ether.
- Asked in CBSE 2024 · 56/1/1 · Q11 · 1 markOrder (CH₃)₃C–OH, (CH₃)₂CH–OH and CH₃CH₂–OH by ease of dehydration with conc. H₂SO₄.
- Asked in CBSE 2024 · 56/1/1 · Q26 · 3 marks(a) Give the mechanism of CH₃CH₂OH → CH₂=CH₂ with H⁺ at 443 K. (b) Main products: (i) CH₃CH₂CH=CH₂ treated with B₂H₆ then H₂O₂/OH⁻; (ii) phenol treated with aq. NaOH, then CO₂ and H⁺.
- Asked in CBSE 2023 · 56/1/1 · Q10 · 1 markOrder of reactivity of 1°, 2° and 3° alcohols in R–OH + HCl (ZnCl₂) → RCl + H₂O.
- Asked in CBSE 2023 · 56/1/1 · Q23(a) · 2 marksExplain: (i) phenol is more acidic than alcohols; (ii) more branching in the alkyl chain lowers an alcohol's boiling point.
- Asked in CBSE 2023 · 56/1/1 · Q23(b) · 2 marks(i) Mechanism of CH₃CH₂OH → CH₂=CH₂ + H₂O with H⁺ at 443 K. (ii) Equation of the Reimer-Tiemann reaction.
- Asked in CBSE 2023 · 56/1/1 · Q28 · 3 marksDo any three conversions: (a) phenol → picric acid; (b) propanone → 2-methylpropan-2-ol; (c) phenol → anisole; (d) propene → propan-1-ol.
Aldehydes, Ketones and Carboxylic Acids
16 questions, 50 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q26 · 3 marksExplain: (a) carboxylic acids boil higher than alcohols of similar molar mass; (b) α-hydrogens of aldehydes and ketones are acidic; (c) ammonia and its derivatives do not add to C=O in strongly acidic medium.
- Asked in CBSE 2026 · 56/1/1 · Q31(a) · 5 marks(i) Compound X is C₅H₁₀O. Give a structure of X if: (I) Tollens' negative, iodoform positive; (II) Tollens' and iodoform negative but it shows aldol condensation; (III) it shows Cannizzaro reaction. (3 marks) (ii) Convert to benzoic acid: (I) acetophenone (II) ethylbenzene. (2 marks)
- Asked in CBSE 2026 · 56/1/1 · Q31(b) · 5 marks(i) Structure of benzaldehyde 2,4-dinitrophenylhydrazone. (ii) Order di-tert-butyl ketone, acetaldehyde, acetone by increasing reactivity with HCN. (iii) A simple test to tell benzoic acid from ethyl benzoate. (iv) Reagent for ethanenitrile → ethanal. (v) Product X when cyclohexanol is treated with CrO₃.
- Asked in CBSE 2025 · 56/1/1 · Q9 · 1 markWhich acid forms when propylmagnesium bromide reacts with CO₂ and the product is hydrolysed with acid?
- Asked in CBSE 2025 · 56/1/1 · Q19 · 2 marksIs benzaldehyde more or less reactive than propanal towards nucleophilic addition? Why?
- Asked in CBSE 2025 · 56/1/1 · Q33(A) · 5 marks(a) Convert (i) ethanal to but-2-enal, (ii) propanoic acid to ethane. (b) Alkene A (C₅H₁₀) on ozonolysis gives B and C. B gives Fehling's test and the iodoform test; C gives iodoform but not Fehling's test. Identify A, B, C.
- Asked in CBSE 2025 · 56/1/1 · Q33(B) · 5 marksCompound A (C₈H₁₆O₂) is hydrolysed by dilute H₂SO₄ into acid B and alcohol C. Chromic acid oxidises C to B, and C on dehydration gives but-1-ene. Identify A, B, C and give the equations.
- Asked in CBSE 2024 · 56/1/1 · Q7 · 1 markWhat does CH₃COOH give with PCl₅?
- Asked in CBSE 2024 · 56/1/1 · Q8 · 1 markAn aldehyde reacting with HCN to give a cyanohydrin is which type of reaction?
- Asked in CBSE 2024 · 56/1/1 · Q15 · 1 markAssertion: ethanoic acid has a lower pKa than ClCH₂COOH. Reason: the −I effect of Cl makes ClCH₂COOH more acidic. Choose the A-R code.
- Asked in CBSE 2024 · 56/1/1 · Q21 · 2 marksWrite the equation and name the reaction: (a) butan-2-one with zinc amalgam and conc. HCl; (b) two moles of benzaldehyde heated with conc. NaOH.
- Asked in CBSE 2024 · 56/1/1 · Q28 · 3 marksEster A (C₆H₁₂O₂) gives B and C with LiAlH₄. B + PCC gives D; D with dil. NaOH then heat gives E; E + H₂ (catalyst) gives C. D oxidises to a monobasic acid F of molar mass 60. Identify A to F.
- Asked in CBSE 2023 · 56/1/1 · Q29(a) · 3 marksWhy: (i) –COOH in benzoic acid directs to meta position; (ii) NaHSO₃ helps purify aldehydes/ketones; (iii) –COOH does not show the usual reactions of C=O?
- Asked in CBSE 2023 · 56/1/1 · Q29(b) · 3 marksCompound A (C₃H₈O) over Cu at 573 K gives B. B does not reduce Fehling's solution but gives a yellow precipitate C with I₂/NaOH. Find A, B, C.
- Asked in CBSE 2023 · 56/1/1 · Q35(a) · 5 marks(i) Convert ethanal into but-2-en-1-al, and convert propanoic acid into 2-chloropropanoic acid. (ii) Alkene A (C₅H₁₀) on ozonolysis gives B and C. B gives Fehling's test and the iodoform test; C gives iodoform but not Fehling's test. Identify A, B, C.
- Asked in CBSE 2023 · 56/1/1 · Q35(b) · 5 marks(i) Chemical test to tell apart (1) CH₃COCH₂CH₃ and CH₃CH₂CH₂CHO, (2) ethanal and ethanoic acid. (ii) Structure of acetone oxime. (iii) CH₃COOH with PCl₅ gives A; A with H₂/Pd–BaSO₄ gives B; B with CH₃MgBr then H₃O⁺ gives C; B with LiAlH₄ gives D. Identify A–D.
Amines
17 questions, 25 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q10 · 1 markWhat product distribution does direct nitration of aniline give?
- Asked in CBSE 2026 · 56/1/1 · Q11 · 1 markWhich has the lowest pKb: C₆H₅N(CH₃)₂, C₆H₅NHCH₃, C₆H₅NH₂ or p-nitroaniline (O₂N–C₆H₄–NH₂)?
- Asked in CBSE 2026 · 56/1/1 · Q29(a)(i) · 1 markIn water, why is CH₃NH₂ a stronger base than (CH₃)₃N?
- Asked in CBSE 2026 · 56/1/1 · Q29(a)(ii) · 1 markIdentify A and B: CH₃CONH₂ with NaOBr gives A; A with C₆H₅COCl in presence of base gives B.
- Asked in CBSE 2026 · 56/1/1 · Q29(b) · 1 markAmine X, C₃H₉N, gives a Hinsberg-reagent product that does not dissolve in alkali. Identify X.
- Asked in CBSE 2026 · 56/1/1 · Q29(b)-OR · 1 markHow is aniline changed into benzonitrile?
- Asked in CBSE 2026 · 56/1/1 · Q29(c) · 1 markWhy is aniline's –NH₂ acetylated before nitration?
- Asked in CBSE 2025 · 56/1/1 · Q10 · 1 markBest reagent to change propanamide into propanamine (same number of carbons)?
- Asked in CBSE 2025 · 56/1/1 · Q20 · 2 marksName A and B: (a) CH₃CH₂Cl + NaCN → A; A + H₂/Ni → B. (b) C₆H₅NH₂ + NaNO₂/HCl at 0–5 °C → A; A + C₆H₅NH₂ in acid (H⁺) → B.
- Asked in CBSE 2025 · 56/1/1 · Q27 · 3 marks(a) Put (CH₃)₂NH, CH₃CH₂NH₂ and CH₃CH₂OH in increasing boiling point. (b) Explain: (i) Gabriel phthalimide synthesis cannot make aromatic primary amines; (ii) amides are weaker bases than amines.
- Asked in CBSE 2024 · 56/1/1 · Q16 · 1 markAssertion: aniline is more basic than NH₃. Reason: resonance makes the N lone pair of aniline less available for a proton. Choose the A-R code.
- Asked in CBSE 2024 · 56/1/1 · Q32 · 5 marksAnswer any five: (a) why N,N-diethylbenzenesulphonamide does not dissolve in alkali; (b) why aniline fails in Friedel-Crafts reactions; (c) a test to tell methylamine from aniline; (d) the Gabriel phthalimide reaction; (e) aniline to p-bromoaniline; (f) product of C₆H₅N₂⁺Cl⁻ with (i) HBF₄ then (ii) NaNO₂/Cu, heat; (g) A and B in C₆H₅COOH –(NH₃, heat)→ A –(Br₂ + NaOH)→ B.
- Asked in CBSE 2023 · 56/1/1 · Q11 · 1 markProduct when CH₃CONH₂ is treated with Br₂ and NaOH (alcoholic).
- Asked in CBSE 2023 · 56/1/1 · Q12 · 1 markLeast basic among (CH₃)₂NH, NH₃, C₆H₅NH₂ and (CH₃)₃N.
- Asked in CBSE 2023 · 56/1/1 · Q15 · 1 markAssertion: –NH₂ directs electrophiles to ortho/para positions. Reason: aniline does not give Friedel-Crafts reaction.
- Asked in CBSE 2023 · 56/1/1 · Q16 · 1 markAssertion: acetylated aniline gives a monosubstituted product. Reason: –NHCOCH₃ activates the ring more than –NH₂.
- Asked in CBSE 2023 · 56/1/1 · Q24 · 2 marksBriefly explain (a) the carbylamine reaction and (b) the Gabriel phthalimide synthesis.
Biomolecules
16 questions, 28 marks across 4 papers
- Asked in CBSE 2026 · 56/1/1 · Q12 · 1 markLack of which vitamin makes red blood cells more fragile and causes muscle weakness?
- Asked in CBSE 2026 · 56/1/1 · Q16 · 1 markAssertion: Glucose pentaacetate gives no reaction with hydroxylamine (H₂N–OH). Reason: This shows that glucose has a free –CHO group.
- Asked in CBSE 2026 · 56/1/1 · Q20 · 2 marksDistinguish: (i) peptide linkage vs glycosidic linkage (ii) essential vs non-essential amino acids.
- Asked in CBSE 2026 · 56/1/1 · Q25 · 3 marksGive the reaction of D-glucose with (a) HI (b) bromine water (c) concentrated HNO₃.
- Asked in CBSE 2025 · 56/1/1 · Q11 · 1 markPick the false statement about glucose: aldohexose; gives n-hexane with HI; exists in furanose form; no Schiff's test.
- Asked in CBSE 2025 · 56/1/1 · Q16 · 1 markA: apart from glycine, all natural α-amino acids are optically active. R: most natural amino acids have L-configuration.
- Asked in CBSE 2025 · 56/1/1 · Q21 · 2 marksWrite the reactions of D-glucose with (a) HCN and (b) bromine water.
- Asked in CBSE 2025 · 56/1/1 · Q28 · 3 marks(a) How does a native protein differ from a denatured one? (b) Which of glucose, lactose, amylose, fructose is a disaccharide? (c) Which vitamin is needed for blood clotting?
- Asked in CBSE 2024 · 56/1/1 · Q3 · 1 markDNA is made of β-D-2-deoxyribose, a heterocyclic base and one more component. Name the third component.
- Asked in CBSE 2024 · 56/1/1 · Q12 · 1 markIn glucose, which two groups react to give the cyclic hemiacetal (pyranose ring)?
- Asked in CBSE 2024 · 56/1/1 · Q19 · 2 marksWhat is formed when D-glucose reacts with (a) HI (prolonged heating) and (b) conc. HNO₃?
- Asked in CBSE 2024 · 56/1/1 · Q27 · 3 marksAnswer any three: (a) define a peptide linkage; (b) bonds holding the two DNA strands together; (c) the polysaccharide among sucrose, glucose, starch, fructose; (d) one water-soluble and one fat-soluble vitamin.
- Asked in CBSE 2023 · 56/1/1 · Q13 · 1 markWhich glycosidic linkage joins the glucose units in the amylose part of starch?
- Asked in CBSE 2023 · 56/1/1 · Q14 · 1 markThe α-helix is a structural feature of which class of substances?
- Asked in CBSE 2023 · 56/1/1 · Q25 · 2 marks(a) Give a reaction proving open-chain D-glucose has a straight (unbranched) carbon chain. (b) Which linkage forms proteins?
- Asked in CBSE 2023 · 56/1/1 · Q30 · 3 marks(a) Hydrolysis products of lactose and of maltose. (b) Basic structural difference between starch and cellulose.