CHSE Odisha 12 Chemistry Sample Paper 2026

COUNCIL OF HIGHER SECONDARY EDUCATION, ODISHA

SAMPLE QUESTION PAPER – 2026

SCIENCE (CHEMISTRY)

605 R/E (Regular/Ex-Regular)

CHEMISTRY

(for students registered in 2023 & 2024)

SET – A

Time : 3 Hours

Full Marks : 70

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Total No. of Printed Pages : 16

[Set Roll No.]

________________

General Instructions :

1. All questions are compulsory.
2. The question paper consists of 38 questions divided into 4 Groups :
• Group – A : Q. No. 1 carries 1 × 7 = 7 marks (Objective/MCQ).
• Group – B : Q. No. 2 to 21 carry 1 × 14 = 14 marks (Very Short Answer).
• Group – C : Q. No. 22 to 33 carry 2 × 12 = 24 marks (Short Answer).
• Group – D : Q. No. 34 to 38 carry 3 × 5 = 15 marks (Long Answer).
3. Figures in the right-hand margin indicate marks.
4. An examinee has to attempt only one of the alternatives in such questions wherever provided.
5. Use of Calculator is prohibited.
6. Answers should be brief and to the point.
7. Draw neat labelled diagrams wherever necessary.

GROUP – A
(Objective Type – Compulsory)

1. Choose and write the correct answer of the following :

(a) The hybridization of carbon in diamond is :

(i) sp³ (ii) sp² (iii) sp (iv) dsp²

(b) Which of the following is a secondary amine ?

(i) CH₃NH₂ (ii) (CH₃)₂NH (iii) (CH₃)₃N (iv) C₆H₅NH₂

(c) The unit of rate constant for a first-order reaction is :

(i) mol L^–1 s^–1 (ii) s^–1 (iii) L mol^–1 s^–1 (iv) L² mol^–2 s^–1

(d) In a face-centered cubic (FCC) unit cell, the number of atoms per unit cell is :

(i) 1 (ii) 2 (iii) 3 (iv) 4

(e) Phenol on reaction with Br₂ water gives :

(i) o-Bromophenol (ii) p-Bromophenol (iii) 2,4,6-Tribromophenol (iv) No reaction

(f) The transition elements show variable oxidation states due to :

(i) Large size (ii) High ionization energy (iii) Availability of d-orbitals (iv) Low electronegativity

(g) The conductivity of strong electrolytes :

(i) Increases on dilution (ii) Decreases on dilution (iii) Remains constant (iv) First increases then decreases

[1 × 7 = 7]

GROUP – B
(Very Short Answer Type – 1 mark each)

2. Define molarity. [1]

3. What is the SI unit of specific conductance ? [1]

4. Write the IUPAC name of CH₃CH(OH)CH₂COOH. [1]

5. Name the product formed when ethanol is heated with conc. H₂SO₄ at 443 K. [1]

6. What is the role of ZnCl₂ in Lucas test ? [1]

7. Define half-life period of a reaction. [1]

8. Write the expression for integrated rate equation for a first-order reaction. [1]

9. What is peptization ? [1]

10. Why do Zr and Hf exhibit similar properties ? [1]

11. Write the formula of potassium hexacyanoferrate(III). [1]

12. What is the coordination number of Cr in [Cr(NH₃)₆]Cl₃ ? [1]

13. Define optical isomerism. [1]

14. What is the geometry of [Ni(CN)₄]^2– ? [1]

15. Name the enzyme used in the conversion of glucose into ethanol. [1]

16. What are biodegradable polymers ? Give one example. [1]

17. What is the monomer of Teflon ? [1]

18. Define nucleophiles. [1]

19. What is the effect of adding a catalyst on the equilibrium constant ? [1]

20. Why is the melting point of p-dichlorobenzene higher than o- and m-isomers ? [1]

21. What is the role of pyridine in the acetylation of aniline ? [1]

[1 × 14 = 14]

GROUP – C
(Short Answer Type – 2 marks each)

22. Explain why the bond angle in NH₃ is less than 109°28′. [2]

23. Define elevation of boiling point. Derive the relationship between elevation of boiling point and molality of the solution. [2]

24. State Kohlrausch’s law of independent migration of ions. Give one application. [2]

25. The rate constant of a first-order reaction is 0.0693 min^–1. Calculate the time taken for 75% completion of the reaction. [2]

26. Explain the mechanism of cannizzaro reaction with suitable example. [2]

27. How will you convert :

(i) Benzene to toluene

(ii) Ethanol to ethene

[2]

28. Explain why phenol is more acidic than ethanol. [2]

29. What are ambident nucleophiles ? Explain with an example. [2]

30. Explain the cleansing action of soap. [2]

31. What is lanthanoid contraction ? Mention one consequence of it. [2]

32. Write the chemical reactions to show that KMnO₄ acts as an oxidizing agent in acidic medium. [2]

33. Explain why [CoF₆]^3– is paramagnetic while [Co(NH₃)₆]³⁺ is diamagnetic. [2]

[2 × 12 = 24]

GROUP – D
(Long Answer Type – 3 marks each)

34.

(a) State and explain Le Chatelier’s principle.

(b) For the equilibrium 2NO(g) + O₂(g) ⇌ 2NO₂(g), predict the effect of :

(i) Increase in pressure

(ii) Addition of inert gas at constant pressure

(iii) Increase in temperature (ΔH = –ve)

OR

(a) Derive the integrated rate equation for a zero-order reaction.

(b) A first-order reaction is 50% complete in 30 minutes. Calculate the rate constant and the time for 90% completion.

[3]

35.

(a) Explain the structure of XeF₆ on the basis of VSEPR theory.

(b) Why is HF a weak acid while HCl is a strong acid ?

(c) Complete the reaction : P₄ + HNO₃ →

OR

(a) Explain the preparation of ozone from oxygen.

(b) Why does nitrogen show inertness ?

(c) Draw the structure of PCl₅ in solid state.

[3]

36.

(a) Explain the mechanism of SN¹ reaction with a suitable example.

(b) Why do alkyl halides show nucleophilic substitution reactions ?

(c) Convert : Chlorobenzene → Phenol

OR

(a) Explain the mechanism of aldol condensation.

(b) How will you distinguish between formaldehyde and acetaldehyde ?

(c) Why do carboxylic acids not give characteristic reactions of carbonyl group ?

[3]

37.

(a) What are essential and non-essential amino acids ? Give two examples of each.

(b) What is denaturation of proteins ?

(c) Why are vitamin C and vitamin B considered as water-soluble vitamins ?

OR

(a) Define : (i) Analgesics (ii) Antiseptics

(b) What are detergents ? How do they differ from soaps ?

(c) Why is the use of aspartame limited to cold foods and drinks ?

[3]

38.

(a) Calculate the packing efficiency in body-centered cubic (BCC) structure.

(b) What is Schottky defect ? Mention one consequence of it.

(c) A metallic element crystallises in FCC lattice with edge length 400 pm. Calculate the density if the atomic mass is 60 g mol^–1.

OR

(a) Explain the following with one example each :

(i) Frenkel defect (ii) F-centers

(b) What is the relationship between molar conductivity and specific conductivity ?

(c) Calculate the EMF of the cell :

Zn | Zn²⁺ (0.1 M) || Cu²⁺ (0.01 M) | Cu

Given : E°(Zn²⁺/Zn) = –0.76 V, E°(Cu²⁺/Cu) = +0.34 V

[3]

[3 × 5 = 15]

Note :

• This sample paper follows the exact blueprint of the 2025 Odisha CHSE Chemistry Question Paper (pattern, marks distribution, question types, and difficulty level).
• All questions are original but aligned with the NCERT syllabus and CHSE examination standards for 2026.
• Diagrams, numericals, and chemical equations are included wherever required as per the original paper.

Prepared for Practice Purpose Only

Best of Luck for CHSE 2026!