MBOSE Class XII Chemistry Sample Question Paper 2027

MBOSE CHEMISTRY SAMPLE PAPER 2027

(Theory)

Full Marks: 70 Time: 3 Hours

General Instructions:

1. All questions are compulsory.
2. Attempt all parts of a question together at one place.
3. There are 33 questions in this question paper with internal choice.
4. Section A consists of 16 multiple-choice questions carrying 1 mark each.
5. Section B consists of 5 short answer-type questions carrying 2 marks each.
6. Section C consists of 7 short answer-type questions carrying 3 marks each.
7. Section D consists of 2 questions carrying 4 marks each.
8. Section E consists of 3 long answer-type questions carrying 5 marks each.

SECTION A

(Marks: 16)

Question Nos. 1 to 16 are multiple-choice questions. Only one of the choices is correct. Select and write the correct choice.

1. The concentration term which does not change with temperature is:

1. Molarity
2. Molality
3. Normality
4. Formality

1

2. For an ideal solution, the enthalpy of mixing is:

1. Positive
2. Negative
3. Zero
4. Infinite

1

3. The unit of the rate constant for a second-order reaction is:

1. s⁻¹
2. L mol⁻¹ s⁻¹
3. mol L⁻¹ s⁻¹
4. L² mol⁻² s⁻¹

1

4. The half-life of a first-order reaction is:

1. Dependent on initial concentration
2. Independent of initial concentration
3. Directly proportional to initial concentration
4. Inversely proportional to initial concentration

1

5. The oxidation state of Mn in KMnO₄ is:

1. +2
2. +4
3. +6
4. +7

1

6. Which property of transition metals is mainly responsible for their ability to form coordination compounds?

1. Large atomic size
2. Availability of vacant orbitals
3. Low melting points
4. Low density

1

7. Which reagent is commonly used to distinguish aldehydes from ketones?

1. Lucas reagent
2. Tollens' reagent
3. Conc. H₂SO₄
4. NaCl solution

1

8. The most acidic compound among the following is:

1. Ethanol
2. Phenol
3. Water
4. Ethane

1

9. Ethanol can be oxidised to ethanal using:

1. PCC
2. LiAlH₄
3. NaBH₄
4. H₂/Ni

1

10. Which compound gives the iodoform test?

1. Methanol
2. Ethanol
3. Propanol
4. tert-Butanol

1

11. Aldol condensation is shown by compounds containing:

1. No carbonyl group
2. α-Hydrogen adjacent to a carbonyl group
3. Only aromatic rings
4. A halogen atom

1

12. The reagent used in the Sandmeyer reaction is:

1. CuCl/CuBr
2. NaOH
3. LiAlH₄
4. KMnO₄

1

13. Which of the following is an aryl halide?

1. CH₃Cl
2. C₂H₅Br
3. C₆H₅Cl
4. CH₂Cl₂

1

14. Which ligand is bidentate?

1. NH₃
2. Cl⁻
3. H₂O
4. Ethane-1,2-diamine

1

15. A complex ion with coordination number 4 can have:

1. Only linear geometry
2. Only tetrahedral geometry
3. Tetrahedral or square-planar geometry
4. Only octahedral geometry

1

16. The non-reducing sugar among the following is:

1. Glucose
2. Fructose
3. Sucrose
4. Maltose

1

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SECTION B

(Marks: 10)

Question Nos. 17 to 21 are very short answer-type questions carrying 2 marks each.

17. Either

(a) Define elevation in boiling point. A solution containing 2.0 g of a non-volatile solute in 50 g of water shows an elevation in boiling point of 0.52 K. Calculate the molar mass of the solute. Given: K_b for water = 0.52 K kg mol⁻¹.

OR

(b) What is osmotic pressure? Why is it considered a colligative property?

18. Either

(a) A first-order reaction has a rate constant of 2.31 × 10⁻³ s⁻¹. Calculate its half-life.

OR

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

19.

(a) Write the IUPAC name of [Co(NH₃)₅Cl]Cl₂. 1

(b) What is linkage isomerism? Give one example. 1

20.

(a) Arrange the following compounds in increasing order of boiling point: CH₃Cl, CH₃CH₂Cl and CH₃CH₂CH₂Cl. 1

(b) Write the major product formed when 2-bromopropane is heated with alcoholic KOH. 1

21.

(a) Complete the reaction:

C₆H₅NH₂ + NaNO₂ + HCl → ?

(b) Why is aniline less basic than ethylamine? 1

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SECTION C

(Marks: 21)

Question Nos. 22 to 28 are short answer-type questions carrying 3 marks each.

22. Either

(a) What is meant by positive deviation from Raoult's law? Give one example and explain its cause.

(b) Calculate the van't Hoff factor for Al₂(SO₄)₃ assuming complete dissociation in water.

OR

(c) Define depression in freezing point.

(d) Calculate the depression in freezing point when 18 g of glucose is dissolved in 100 g of water. Given: K_f = 1.86 K kg mol⁻¹; molar mass of glucose = 180 g mol⁻¹.

23.

(a) For the cell reaction:

Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Calculate the standard Gibbs energy change if E^°_cell = 1.10 V. Given: F = 96500 C mol⁻¹.

(b) What does a positive value of E^°_cell indicate about a cell reaction?

24. Either

(a) Differentiate between order and molecularity of a reaction.

(b) For the reaction 2A → B, the rate of disappearance of A is 4.0 × 10⁻³ mol L⁻¹ s⁻¹. Calculate the rate of formation of B.

OR

(c) The rate law for a reaction is:

r = k[A]²[B]

Find the overall order of the reaction.

(d) State one difference between an elementary reaction and a complex reaction.

25. Either

(a) Explain the SN2 mechanism using the reaction of bromoethane with aqueous hydroxide ion.

(b) Why are tertiary alkyl halides generally more reactive than primary alkyl halides towards SN1 reactions?

OR

(c) Carry out the following conversions:

1. Ethene to ethanol
2. Aniline to chlorobenzene
3. 1-bromopropane to propan-1-ol

26.

(a) Write the chemical equation for the preparation of anisole by Williamson ether synthesis.

(b) How will you convert:

1. Phenol into picric acid
2. Ethanol into ethanoic acid

OR

(c) Arrange the following in increasing order of acidity: ethanol, phenol and p-nitrophenol.

(d) Give the major product of phenol with bromine water.

27.

(a) Arrange the following in decreasing order of basic strength: NH₃, CH₃NH₂, (CH₃)₂NH and aniline.

(b) Identify the products A and B:

CH₃CH₂Br → KCN → A → LiAlH₄ → B

28. Either

(a) Name the four nitrogenous bases present in DNA.

(b) What is denaturation of proteins?

(c) What are essential amino acids? Give one example.

OR

(d) Distinguish between reducing and non-reducing sugars.

(e) What is meant by a peptide bond? Write its general structure.

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SECTION D

(Marks: 8)

Question Nos. 29 and 30 carry 4 marks each.

29.

(a) Calculate the oxidation number of Co in [Co(NH₃)₅Cl]Cl₂. 1

(b) Give one example of a tetrahedral complex. 1

(c) Which of the following is an inner-orbital complex: [Co(NH₃)₆]³⁺ or [CoF₆]³⁻? Give reason. 1

(d) Why are coordination compounds generally coloured? 1

30.

(a) What are monosaccharides? Give one example. 1

(b) What are epimers? Give one example. 1

(c) Name one optically active amino acid. 1

(d) Why does glucose form an oxime with hydroxylamine? 1

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SECTION E

(Marks: 15)

Question Nos. 31 to 33 are long answer-type questions carrying 5 marks each.

31. Either

(a) Define conductivity and molar conductivity. 1

(b) Calculate the EMF of the cell:

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

Given E^°_cell = 1.10 V at 298 K. 2

(c) What is cathodic protection? Explain its principle. 2

OR

(d) State Kohlrausch's law of independent migration of ions. 1

(e) Explain why molar conductivity increases on dilution. 1

(f) Calculate the molar conductivity of CH₃COOH at infinite dilution using:

Λ°(HCl) = 426 S cm² mol⁻¹
Λ°(CH₃COONa) = 91 S cm² mol⁻¹
Λ°(NaCl) = 126 S cm² mol⁻¹

3

32. Either

(a) Why do transition metal ions generally form coloured compounds? 1

(b) Write the structure of the permanganate ion. 1

(c) Explain why Mn²⁺ is particularly stable among the first-row transition-metal ions. 1

(d) Write balanced equations for the reactions of KMnO₄ with:

1. FeSO₄ in acidic medium
2. Oxalic acid in acidic medium

2

OR

(e) Why do transition metals readily form alloys? 1

(f) Why is zinc not considered a transition element? 1

(g) Write the balanced equation for the oxidation of iodide ion by KMnO₄ in acidic medium. 1

(h) Describe briefly the preparation of KMnO₄ from pyrolusite ore. 2

33. Either

(a) Why is benzaldehyde less reactive than ethanal towards nucleophilic addition reactions? Explain. 2

(b) Identify the products A, B and C in the following sequence:

CH₃CH₂Br → Mg/dry ether → A → CO₂ → B → H₃O⁺ → C

2

(c) Predict the product of the reaction of ethanal with dilute NaOH followed by heating. 1

OR

(d) Write the structures of pentan-2-one and pentan-3-one. How would you distinguish between them using a chemical test? 2

(e) Identify the products A and B:

C₆H₅NO₂ → Sn/HCl → A → CHCl₃/alc. KOH → B

2

(f) The pK_a values of benzoic acid, p-nitrobenzoic acid and p-methoxybenzoic acid are 4.20, 3.44 and 4.47, respectively. Which acid is strongest? Give a reason. 1

MBOSE Class XII Chemistry — Sample Question Paper
Designed according to the structure and marks distribution according to 2026 Chemistry theory paper.