Prepare for the Grade 11 Annual Examination 2027 with the ALP Smart Syllabus Solved Chemistry Model Paper 2027, developed according to the latest smart syllabus issued by PECTAA Punjab. These Punjab Board 2027 Model Papers are designed to help students prepare effectively for their 11th Class Chemistry examination. The study material includes a Full Book Test Series and Chapter Wise Test Series, along with solved questions to support exam preparation and strengthen subject knowledge. Students can use these Class 11 Chemistry solved model papers to revise important topics, practise examination-style questions, and prepare according to the new PECTAA ALP Smart Syllabus 2026–27 for the Annual Examination 2027.
MODEL PAPER OF CHEMISTRY FOR CLASS-11
Objective Type
Q-1: Four possible answers A, B, C and D to each question are given. The choice which you think is correct, fill that circle with marker or pen ink in the answer-book. Cutting or filling two or more circles will result in zero mark in that question.
(i) Which is the oxidation state of sulfur in the sulfate ion (SO42−)?
(A) +4(B) +2(C) +6(D) 0
(C) +6. Let S = x: x + 4(−2) = −2, so x = +6.
(ii) Which of the following elements have the highest ionization energy?
(A) Sodium (Na)(B) Megnesium (Mg)(C) Aluminum (Al)(D) Argon (Ar)
(D) Argon. It is a noble gas at the right end of period 3 with a stable octet and the smallest size, so its ionization energy is highest.
(iii) How many ‘d’ orbitals are there in a given energy level?
(A) 1(B) 3(C) 5(D) 7
(C) 5. For d, l = 2, so m = −2, −1, 0, +1, +2 (2l + 1 = 5).
(iv) The enthalpy of neutralization of NaOH and HCl is?
(A) − 57.1 kJ mol−1(B) + 436 kJ mol−1(C) −27.8 kJ mol−1(D) 01 kJ mol−1
(A) −57.1 kJ mol−1. H+ + OH− → H2O is exothermic for a strong acid and a strong base.
(v) The number of σ and π bonds in the N2 molecule are:
(A) One σ and one π bond(B) One σ and two π bonds(C) Three σ bonds only(D) Two σ and one π bond
(B). N≡N is a triple bond: one σ bond (head-on overlap) and two π bonds (sideways overlap).
(vi) Which one of the following has the greatest mass?
(A) 0.5 mol of N2(B) 0.5 mol of NH3(C) 0.5 mol of He(D) 0.5 mol of CO2
(D). Mass = 0.5 × molar mass: N2 14 g, NH3 8.5 g, He 2 g, CO2 22 g. CO2 is greatest.
(vii) When water freezes at 0 °C, its density decreases due to:
(A) Cubic structure of ice(B) Decrease in volume(C) Decrease in density(D) Empty spaces in structure of ice
(D). Hydrogen bonding forms an open hexagonal cage with empty spaces, so volume increases and density falls.
(viii) The enthalpy change for a reaction depends on:
(A) Pathway taken from reactants to products(B) Presence of catalyst(C) Initial and final states of reactants and products(D) Rate of reaction
(C). Enthalpy is a state function (Hess’s law): it does not depend on the path, catalyst or rate.
Model Paper – Page 1 of 5
(ix) The order of chemical reaction that is independent of concentration is:
(A) Second order reaction(B) First order reaction(C) Zero order reaction(D) Pseudo first order reaction
(C). Rate = k[A]0 = k, so the rate does not change with concentration.
(x) For a specific reaction, the value of the equilibrium constant Kc:
(A) Always remain the same at different reaction conditions.(B) Increases if the concentration of one of the products is increased(C) Changes with changes in the temperature(D) Increases if the concentration of one of the reactants is increased
(C). Kc depends only on temperature (not on concentration, pressure or catalyst).
(xi) Which of the following pairs forms a buffer solution?
(A) HCl and NaCl(B) CH3COONa and CH3COOH(C) HCl and NaOH(D) NH3 and Na2SO4
(B). A buffer is a weak acid with its salt (conjugate base): CH3COOH / CH3COONa.
(xii) If the salt bridge is not used between two half cells in a Galvanic cell, then the voltage:
(A) Decreases slowly(B) Decreases rapidly(C) Does not change(D) Drop to zero
(D). The circuit is incomplete and charge builds up in the half cells, so the cell stops working and the voltage drops to zero.
(xiii) Which of the following statements about a photovoltaic cell is correct?
A) It converts chemical energy directly into electrical energy.B) It converts light energy directly into electrical energy.C) It converts electrical energy into light energy.D) It stores energy like a battery.
(B). A photovoltaic (solar) cell turns light energy directly into electricity.
(xiv) The most stable carbonium ion among the following is:
(A) CH3+(B) CH3CH2+(C) (CH3)2CH+(D) (CH3)3C+
(D). The tertiary carbocation has three electron-donating alkyl groups (inductive effect and hyperconjugation) that spread the positive charge.
(xv) Peroxyacetyl nitrate (PAN) formation starts when ______ reacts with the hydrocarbons.
(A) NO(B) NO2(C) O3(D) H2O
(C) O3. Ozone (formed from NO2 photolysis) attacks hydrocarbons to give peroxyacetyl radicals, which then combine with NO2 to give PAN.
(xvi) Which of the halogen molecules has the strongest bond?
(A) F2(B) Br2(C) Cl2(D) I2
(C) Cl2 (243 kJ mol−1). F2 is weaker because of repulsion between lone pairs on its very small atoms.
(xvii) Which gas causes yellow colour in photochemical smog?
(A) CO(B) SO3(C) NO2(D) SO2
(C) NO2. It is a reddish-brown gas that gives the yellowish-brown haze.
Model Paper – Page 2 of 5
Subjective Type (Part-I)
Q. 2: Write short answers to any eight (08) questions:(2 × 8 = 16)
i. What is 1st ionization energy? Give an example.
The minimum energy needed to remove the most loosely held electron from one mole of isolated gaseous atoms. Example: Na(g) + 496 kJ mol−1 → Na+(g) + e−.
ii. What are the factors that affect the electronegativity?
(1) Atomic size: smaller atoms attract bonding electrons more strongly. (2) Nuclear charge: higher effective nuclear charge raises electronegativity. (3) Shielding by inner electrons lowers it.
iii. Why oxides of sodium and magnesium are more ionic than the oxides of nitrogen and phosphorus?
Na and Mg have low electronegativity, so the difference with oxygen is large (>1.7) and they transfer electrons to form ionic oxides. N and P have electronegativity close to oxygen, so they share electrons and form covalent oxides.
iv. There are three orientations of p-orbital due to three values of magnetic quantum number. Justify it.
For a p-orbital l = 1, and m = −l to +l gives −1, 0, +1 (2l + 1 = 3). These are the orbitals px, py, pz directed along the x, y and z axes.
v. What is the purpose of Azimuthal Quantum Number and how is it represented?
It gives the shape of the orbital (subshell) and its angular momentum. It is represented by l, with values 0 to (n − 1): 0 = s, 1 = p, 2 = d, 3 = f.
vi. What do you understand by the rate of reaction?
The change in concentration of a reactant or product per unit time. Unit: mol dm−3 s−1.
vii. Differentiate between order and molecularity of a reaction?
Order is the sum of the powers of concentrations in the rate law; it is found by experiment and can be zero or fractional. Molecularity is the number of molecules colliding in an elementary step; it is a whole number (1, 2, 3).
viii. What is meant by the state of chemical equilibrium?
In a reversible reaction, the state at which the rates of forward and reverse reactions are equal, so concentrations of reactants and products stay constant.
ix. Write two characteristics of equilibrium constant.
(1) Kc has a fixed value at a given temperature and does not depend on initial concentrations. (2) It is unaffected by a catalyst and changes only with temperature.
x. Why HF is weaker acid than HCl?
The H–F bond is very short and strong (565 kJ mol−1), and HF is hydrogen-bonded, so it ionizes only slightly. The H–Cl bond is weaker, so HCl ionizes almost completely.
xi. Which halogen is the least reactive, which is the most reactive? Give reason.?
Iodine is the least reactive and fluorine the most reactive. Reactivity falls down the group as atomic size increases and electronegativity (oxidizing power) decreases.
xii. How does the reactivity of halogens with hydrogen vary?
F2 reacts explosively even in the dark; Cl2 explosively in sunlight; Br2 only on heating with a catalyst; I2 slowly and reversibly on strong heating. Reactivity decreases F > Cl > Br > I.
Model Paper – Page 3 of 5
Q. 3: Write short answers to any eight (08) questions:(2 × 8 = 16)
i. Explain the difference between the formation of σ and π bonds in terms of Valence Bond Theory (VBT).
A σ bond forms by head-on (axial) overlap of orbitals along the internuclear axis; it is strong. A π bond forms by sideways overlap of parallel p-orbitals above and below the axis; it is weaker.
ii. Define bond order with one example.
Bond order = ½ (number of electrons in bonding MOs − number in antibonding MOs). Example: N2 = ½(10 − 4) = 3.
iii. Define sp2 hybridization with suitable example.
Mixing of one s and two p orbitals to give three equivalent sp2 orbitals at 120° (trigonal planar). Example: BF3, C2H4.
iv. Explain, at the molecular level, why evaporation leads to a cooling effect.
The fastest (highest kinetic energy) molecules escape from the surface, so the average kinetic energy of the remaining molecules falls and the liquid cools.
v. Why does the boiling point of a liquid increase when the external pressure rises?
A liquid boils when its vapour pressure equals the external pressure. Higher external pressure needs a higher temperature to reach it.
vi. What factors influence the magnitude of the lattice enthalpy?
(1) Charge on the ions: higher charge gives larger lattice enthalpy. (2) Ionic size: smaller ions give larger lattice enthalpy.
vii. Why does wood burn more rapidly in pure oxygen than in air?
Air has only about 21% O2, diluted by N2. Pure oxygen has a higher concentration, so collisions are more frequent and the rate is faster.
viii. Why does common ion effect decrease solubility of a less soluble salt?
The added common ion shifts the dissolution equilibrium backwards (Le Chatelier’s principle), so some salt precipitates and its solubility falls.
ix. How does a buffer maintain pH stability?
Added H+ is consumed by the conjugate base, and added OH− is neutralized by the weak acid, so the pH changes very little.
x. Differentiate between aliphatic and aromatic hydrocarbons.
Aliphatic hydrocarbons are open-chain or non-benzene ring compounds (alkanes, alkenes). Aromatic hydrocarbons contain a benzene ring with delocalized π electrons and special stability, e.g. benzene.
xi. Explain why alkanes do not undergo addition reactions.
Alkanes are saturated; they have only strong σ bonds and no π bond to open. They therefore undergo substitution instead.
xii. Define enthalpy change of Atomization with a suitable example.
The enthalpy change when one mole of gaseous atoms is formed from the element in its standard state. Example: Na(s) → Na(g), ΔHat ≈ +107 kJ mol−1.
Q. 4: Write short answers to any six (06) questions:(2 × 6 = 12)
i. List two reasons for inertness of N2.
(1) Very strong N≡N triple bond (944 kJ mol−1). (2) Non-polar molecule with no easily attacked site.
ii. What is the construction and function of a catalytic converter?
A steel chamber holding a ceramic honeycomb coated with Pt, Pd and Rh. It converts CO to CO2, unburnt hydrocarbons to CO2 and H2O, and NOx to N2.
iii. Identify and briefly explain two major natural sources of air pollutants.
(1) Volcanic eruptions release SO2, H2S and ash. (2) Forest fires release CO, CO2 and smoke particles.
iv. How do Chlorofluorocarbons (CFCs) cause depletion of Ozone?
UV breaks CFCs to give Cl atoms: CFCl3 → Cl• + •CFCl2. Then Cl• + O3 → ClO• + O2 and ClO• + O → Cl• + O2. The chain repeats and one Cl atom destroys thousands of O3 molecules.
v. How is the concept of mole derived from Avogadro’s number?
One mole is the amount of substance containing 6.022 × 1023 particles (Avogadro’s number), the number of atoms in 12 g of carbon-12.
vi. What is stoichiometry? Give the basic assumptions of stoichiometric calculations.
It is the study of the quantitative relationship between reactants and products. Assumptions: reactants are pure, the reaction goes to completion, there are no side reactions, and mass is conserved.
vii. How and why electrical double layer is formed?
When a metal is dipped in a solution of its ions, M ⇌ Mn+ + ne−. The rod gains negative charge while Mn+ ions gather near it, forming a layer of opposite charges at the interface. This happens because the metal tends to lose (or gain) ions to reach equilibrium.
viii. During electrolysis of NaCl, why is Na not liberated at cathode?
In aqueous solution, water is reduced more easily (E° = −0.83 V) than Na+ (E° = −2.71 V), so H2 is liberated and not Na.
ix. What are the advantages of salt bridge in a galvanic cell?
It completes the circuit, keeps both half cells electrically neutral by ion migration, and prevents mixing of the two solutions.
Model Paper – Page 4 of 5
Subjective Type (Part II)
Note: Attempt any three questions.
Q.5:
(a) What are quantum numbers? Describe briefly principal and spin quantum numbers. (4)
Quantum numbers are numbers that describe the energy, size, shape and orientation of an orbital and the spin of an electron. Principal (n): n = 1, 2, 3… gives the shell, its size and energy; a shell holds up to 2n2 electrons. Spin (ms): +½ or −½, showing the clockwise or anticlockwise spin of the electron; an orbital holds two electrons of opposite spin.
(b) Discuss structural changes when water turns into ice. Justify the empty spaces in its crystals as compared to H2O at 40 °C and lower density of ice. (4)
In liquid water, molecules are close and keep breaking and forming hydrogen bonds. On freezing, each molecule forms four hydrogen bonds with tetrahedrally arranged neighbours, giving an open hexagonal cage with empty spaces. Molecules are held farther apart than in the liquid, so the volume increases and the density falls (0.92 g cm−3), so ice floats. (Liquid water is densest at 4 °C.)
Q.6:
(a) Explain the orbital hybridization in NH3 and BF3. (4)
NH3: one 2s and three 2p orbitals of N mix to give four sp3 orbitals. Three overlap with H 1s orbitals and one holds the lone pair, so the shape is pyramidal (H–N–H ≈ 107°). BF3: B (2s12p2 after excitation) mixes one s and two p orbitals to give three sp2 orbitals that overlap with F 2p orbitals, so the shape is trigonal planar (120°).
(b) Define catalysis and explain two types with one example each. (4)
Catalysis is the change in rate of a reaction by a substance (catalyst) that is recovered unchanged at the end. Homogeneous: catalyst and reactants are in the same phase, e.g. 2SO2(g) + O2(g) → 2SO3(g) with NO(g). Heterogeneous: different phases, e.g. N2(g) + 3H2(g) → 2NH3(g) with solid Fe (Haber process).
Q.7:
(a) Define and explain the law of mass action and derive the expression for the equilibrium constant. (4)
The rate of a chemical reaction is proportional to the product of the active masses (molar concentrations) of the reactants, each raised to the power of its coefficient. For aA + bB ⇌ cC + dD: forward rate = kf[A]a[B]b; reverse rate = kr[C]c[D]d. At equilibrium the rates are equal, so
Kc = kf/kr = [C]c[D]d / [A]a[B]b
(b) In a solution, the pH is 9.2, determine the product of water Kw at 25 °C. (4)
pOH = 14 − 9.2 = 4.8. [H+] = 10−9.2 = 6.31 × 10−10 M; [OH−] = 10−4.8 = 1.58 × 10−5 M.
Kw = [H+][OH−] = 1.0 × 10−14 mol2 dm−6
Q.8:
(a) Describe the following methods for the preparation of alkenes: (2, 2)
i. Dehydrohalogenation of alkyl halides
ii. Dehydration of alcohol
i. Heating an alkyl halide with alcoholic KOH removes H and X from adjacent carbons:
CH3CH2Br + KOH(alc.) → CH2=CH2 + KBr + H2O
ii. Heating an alcohol with conc. H2SO4 at 170 °C (or passing vapours over Al2O3 at 350 °C) removes water:
CH3CH2OH → CH2=CH2 + H2O
(b) How does the burning of fossil fuel cause acid rain? Discuss in detail the chemical reaction. (4)
Fossil fuels contain sulfur and, at high temperature, N2 and O2 combine. Oxides of sulfur and nitrogen form:
S + O2 → SO2; 2SO2 + O2 → 2SO3; SO3 + H2O → H2SO4
N2 + O2 → 2NO; 2NO + O2 → 2NO2; 4NO2 + O2 + 2H2O → 4HNO3
These acids dissolve in rain water and lower its pH below 5.6, giving acid rain.
Q.9:
(a) How do the oxides of nitrogen (NOx) cause the formation of chemical smog and PAN? Give its mechanism. (4)
Sunlight splits NO2, and the oxygen atom forms ozone, which attacks hydrocarbons:
NO2 + hν → NO + O; O + O2 → O3; NO + O3 → NO2 + O2
O3 + hydrocarbons → aldehydes and peroxyacetyl radicals (CH3COO2•)
CH3COO2• + NO2 → CH3COO2NO2 (PAN)
The mixture of O3, aldehydes, PAN and NO2 with fog forms the photochemical smog.
(b) Describe the volatility of halogens and also explain its trends in detail. (4)
F2 (b.p. −188 °C) and Cl2 (−34 °C) are gases, Br2 (59 °C) is a volatile liquid and I2 (184 °C) is a solid that sublimes. Volatility therefore decreases down the group: F2 > Cl2 > Br2 > I2. Molecules become larger with more electrons, so London dispersion forces between them get stronger and more energy is needed to separate them.
Model Paper – Page 5 of 5
Source: PECTAA Model Paper of Chemistry for Class-11, Annual Exam-2027. Answers are provided as a study aid.
