PSEB CLASS 12 CHEMISTRY SAMPLE PAPER 2026 SET 2 ( SEPTEMBER EXAMINATION)

CLASS-XII: CHEMISTRY (THEORY)

Term-1 / September Examination (2026–27)

Time Allowed: 3 Hours | Maximum Marks: 70

General Instructions

1. There are 21 questions in this question paper with internal choice.

2. SECTION A consists of 1 question (Q1) with 18 sub-parts carrying 1 mark each. Sub-parts (i) to (xvi) are Multiple Choice Questions, and (xvii) to (xviii) are Assertion-Reasoning questions.

3. SECTION B consists of 12 Very Short Answer questions (Q2 to Q13) carrying 2 marks each. Internal choice is provided in three questions.

4. SECTION C consists of 6 Short Answer & Case Study questions (Q14 to Q19) carrying 3 marks each. Internal choice is provided in two questions. Q19 is a Case Study question.

5. SECTION D consists of 2 Long Answer questions (Q20 and Q21) carrying 5 marks each. Internal choice is provided in both questions.

6. Use of log tables and unprogrammable calculators is allowed.

Blue Print & Weightage Summary

Chapter Name	Section A (1M)	Section B (2M)	Section C (3M)	Section D (5M)	Total Marks
1. Solutions	3 (3M)	2 (4M)	1 (3M)	—	10 Marks
2. Electrochemistry	3 (3M)	2 (4M)	—	1 (5M)	12 Marks
3. Chemical Kinetics	3 (3M)	2 (4M)	1 (3M)	—	10 Marks
4. d- and f-Block Elements	3 (3M)	2 (4M)	1 (3M)	1 (5M)	15 Marks
5. Coordination Compounds	3 (3M)	2 (4M)	2 (6M)	—	13 Marks
6. Biomolecules	3 (3M)	2 (4M)	1 (3M)	—	10 Marks
Total Marks	18 Marks	24 Marks	18 Marks	10 Marks	70 Marks

SECTION A (18 Marks)

Q1. Select and write the most appropriate option for the following sub-parts:

(i) While doing an experiment, a student adds glucose (C₆H₁₂O₆) to water and measures the change in vapor pressure. Which colligative property is being studied?

(a) Osmosis (b) Elevation of boiling point (c) Relative lowering of vapor pressure (d) Depression in freezing point

(ii) According to Raoult's law, the vapour pressure of a solvent is directly proportional to its:

(a) Molarity (b) Mole fraction (c) Molality (d) Density

(iii) A student measures the osmotic pressure of different solutions at the same temperature. He finds that osmotic pressure is directly proportional to concentration. This relation is analogous to:

(a) Boyle's law (b) Avogadro's law (c) Ideal gas law (d) Charles's law

(iv) The standard electrode potential of a half-cell depends on:

(a) Concentration, pressure, and temperature (b) Only the temperature (c) Only concentration of ions (d) Nature of electrodes only

(v) An iron bridge near the sea is protected by attaching blocks of zinc to it. This method works because:

(a) Zinc forms a waterproof coating on iron (b) Zinc is more reactive than iron and oxidizes first (c) Zinc prevents oxygen from reaching iron (d) Zinc reacts with water to neutralize acids

(vi) What are the units of the rate constant (k) for a zero-order reaction?

(a) s⁻¹ (b) mol L⁻¹ s⁻¹ (c) L mol⁻¹ s⁻¹ (d) L² mol⁻² s⁻¹

(vii) The rate of a chemical reaction generally increases with an increase in temperature because of:

(a) Decrease in activation energy (b) Increase in the number of effective collisions (c) Decrease in collision frequency (d) Increase in the threshold energy

(viii) In a reaction, if the concentration of a reactant drops from 1.0 M to 0.5 M in 20 minutes, and from 0.5 M to 0.25 M in the next 20 minutes, the order of the reaction is:

(a) Zero (b) First (c) Second (d) Third

(ix) Which of the following is a property of lanthanoids?

(a) Constant ionic radius across the series (b) Gradual decrease in ionic size with increasing atomic number (c) No variable oxidation states (d) Colourless compounds only

(x) A student compared magnetic properties of Fe²⁺ and Fe³⁺ ions. Fe²⁺ shows 4 unpaired electrons while Fe³⁺ shows 5 unpaired electrons. Which statement is correct?

(a) Fe²⁺ is more paramagnetic (b) Fe³⁺ is more paramagnetic (c) Both are diamagnetic (d) Both show equal magnetic moment

(xi) Which transition metal compound acts as a catalyst in the Contact Process because of its ability to undergo changes in oxidation state?

(a) MnO₂ (b) V₂O₅ (c) CuO (d) ZnO

(xii) The IUPAC name of [Co(NH₃)₆]Cl₃ is:

(a) Hexaamminecobalt(III) chloride (b) Hexaamminecobalt(II) chloride (c) Hexaammoniacobalt trichloride (d) Cobalthexammine chloride

(xiii) Which of the following complexes shows linkage isomerism?

(a) [Co(NH₃)₆]³⁺ (b) [Co(NO₂)(NH₃)₅]²⁺ (c) [Fe(CN)₆]⁴⁻ (d) [NiCl₄]²⁻

(xiv) The hybridization of the central metal atom in [Ni(CN)₄]²⁻ is:

(a) sp³ (b) dsp² (c) sp² (d) sp³d²

(xv) Which base is present in RNA but not in DNA?

(a) Uracil (b) Cytosine (c) Guanine (d) Thymine

(xvi) The helical structure of a protein is stabilized by:

(a) Peptide bond (b) Hydrogen bond (c) van der Waals forces (d) Dipole association

Directions for sub-parts (xvii) and (xviii):

In each question, an Assertion (A) is followed by a Reason (R). Choose the correct option:

(a) Both (A) and (R) are true, and (R) is the correct explanation of (A). (b) Both (A) and (R) are true, but (R) is not the correct explanation of (A). (c) (A) is true, but (R) is false. (d) (A) is false, but (R) is true.

(xvii)

Assertion (A): The emf of a Daniell cell increases when the concentration of Cu²⁺ ions is increased.

Reason (R): According to the Nernst equation, cell emf depends on the concentration of ions in solution.

(xviii)

Assertion (A): Glucose is a reducing sugar.

Reason (R): Glucose contains a free aldehydic group in its open-chain structure.

SECTION B (24 Marks)

Q2. A solution contains 5% by mass of urea (CH₄N₂O) in water. Calculate the molarity of the solution, given that the density of the solution is 1.10 g/mL. (2 Marks)

Q3. Given the vapor pressure of pure water at 298 K is 23.8 mm Hg, and a solution has a vapor pressure of 22.8 mm Hg, calculate the mole fraction of solute in the solution. (2 Marks)

Q4. What amount of electricity (in Coulombs or Faradays) can deposit 1 mole of calcium metal at the cathode when passed through molten CaCl₂? (2 Marks)

Q5. The resistance of 0.5 N solution of an electrolyte in a conductivity cell was found to be 25 Ω. Calculate the equivalent conductivity of the solution if the electrodes in the cell are 1.6 cm apart and have an area of 3.2 cm². (2 Marks)

OR

The molar conductances at infinite dilution for sodium acetate (CH₃COONa), hydrochloric acid (HCl), and sodium chloride (NaCl) are 95.5, 426.9, and 120.4 S cm² mol⁻¹ respectively at 298 K. Calculate the molar conductance of acetic acid (CH₃COOH) at infinite dilution. (2 Marks)

Q6. Define a pseudo first-order reaction and illustrate it with a balanced chemical equation. (2 Marks)

Q7. Calculate the half-life of a first-order reaction having rate constant k = 200 s⁻¹. (2 Marks)

Q8. Explain why zinc (Zn) and cadmium (Cd) are normally not considered transition metals. (2 Marks)

Q9. Zn²⁺ ion is colourless whereas Cu²⁺ ion is coloured in aqueous solutions. Explain with reason. (2 Marks)

OR

Why are Fe³⁺ compounds more stable than Fe²⁺ compounds towards oxidation? (2 Marks)

Q10. Define a ligand. Give two examples of bidentate ligands. (2 Marks)

Q11. Write the hybridization and geometry/shape of [Ni(CO)₄]. (2 Marks)

Q12. What is a peptide linkage/bond? Illustrate with an example. (2 Marks)

Q13. Differentiate between essential and non-essential amino acids. (2 Marks)

OR

Why cannot Vitamin C be stored in the human body? (2 Marks)

SECTION C (18 Marks)

Q14. Addition of 0.643 g of a non-volatile compound to 50 mL of benzene (density = 0.879 g/mL) lowers the freezing point from 5.51 °C to 5.03 °C. If K_f for benzene is 5.12 K kg mol⁻¹, calculate the molecular mass of the compound. (3 Marks)

Q15. A first-order reaction is 20% complete in 10 minutes. Calculate the time required for 75% completion of this reaction. (3 Marks)

OR

The rate constant of a first-order reaction increases from 2.5 × 10⁻² s⁻¹ to 5.0 × 10⁻² s⁻¹ when the temperature is raised from 300 K to 310 K. Calculate the activation energy (E_a) of the reaction (R = 8.314 J K⁻¹ mol⁻¹). (3 Marks)

Q16. What is meant by 'lanthanoid contraction'? State its primary cause and describe two major consequences on the chemistry of post-lanthanoid elements. (3 Marks)

Q17. Write the systematic IUPAC names of the following coordination entities: (3 Marks)

(i) [Co(en)₂Cl₂]⁺

(ii) [Cr(NH₃)₄Cl₂]Cl

(iii) K₂[PdCl₄]

OR

Using Valence Bond Theory (VBT), explain why [Ni(CO)₄] is diamagnetic while [NiCl₄]²⁻ is paramagnetic. (3 Marks)

Q18. Draw the crystal field splitting diagram of d-orbitals in an octahedral coordination field (Δ_o). Explain how the magnitude of crystal field splitting determines the formation of low-spin vs high-spin complexes. (3 Marks)

Q19. CASE STUDY QUESTION

Read the passage below and answer the questions that follow:

Proteins are high molecular mass biopolymers of α-amino acids joined together by peptide bonds. They play a fundamental role in physiological structure and metabolic regulation. In native proteins, the secondary and tertiary structures are stabilized by hydrogen bonding, disulfide linkages, and van der Waals interactions. When a native protein is subjected to physical changes such as temperature or chemical changes like alteration of pH, these non-covalent interactions are disrupted. As a result, globules unfold and helices get uncoiled, leading to loss of biological function without cleaving the covalent peptide backbone.

(a) Name the type of chemical linkage formed between −COOH and −NH₂ groups of adjacent amino acids in a protein chain. (1 Mark)

(b) Differentiate between fibrous proteins and globular proteins on the basis of shape and solubility. (1 Mark)

(c) What happens to the primary structure of a protein during denaturation? Give one common daily-life example of protein denaturation. (1 Mark)

SECTION D (10 Marks)

Q20.

(a) For the galvanic cell:

Zn(s) | Zn²⁺(0.0004 M) || Cd²⁺(0.2 M) | Cd(s)

Calculate the cell EMF (E_cell) at 298 K and find the standard Gibbs free energy change (ΔG°) for the reaction.

[Given: E°(Zn²⁺/Zn) = −0.76 V, E°(Cd²⁺/Cd) = −0.40 V, 1 F = 96,500 C mol⁻¹] (3 Marks)

(b) State Faraday's first law of electrolysis. A steady current of 4 A is passed through an aqueous solution of CuSO₄ for 2 hours. Calculate the mass of copper deposited at the cathode.

[Molar mass of Cu = 63.5 g mol⁻¹, 1 F = 96,500 C mol⁻¹] (2 Marks)

OR

(a) Represent the electrochemical cell and calculate its EMF (E_cell) at 298 K for the reaction:

Mg(s) + Cu²⁺(0.0001 M) → Mg²⁺(0.001 M) + Cu(s)

[Given: E°(Mg²⁺/Mg) = −2.37 V, E°(Cu²⁺/Cu) = +0.34 V] (3 Marks)

(b) Give reasons for the following:

(i) Write the chemical reactions occurring at the cathode and anode of a Hydrogen-Oxygen fuel cell.

(ii) Zinc blocks attached to the hull of steel ships protect iron from corrosion even if scratched. (2 Marks)

Q21.

(a) Account for the following:

(i) Transition metals show variable oxidation states.

(ii) Zn, Cd, and Hg are soft metals with comparatively low melting and boiling points.

(iii) E° value for the Mn³⁺/Mn²⁺ couple is highly positive (+1.57 V) compared to Cr³⁺/Cr²⁺. (3 Marks)

(b) Write one point of similarity and one point of difference between the chemistry of lanthanoids and actinoids. (2 Marks)

OR

(a) Explain the following observations:

(i) Transition metals and their compounds are effective industrial catalysts.

(ii) Zirconium (Zr, Z=40) and Hafnium (Hf, Z=72) have almost identical atomic and ionic radii.

(iii) KMnO₄ exhibits an intense purple colour despite the absence of unpaired d-electrons on Mn⁷⁺. (3 Marks)

(b) Write the chemical formulae of:

(i) Manganate ion

(ii) Dichromate ion

What is Misch metal? State one of its major uses. (2 Marks)