Class: 12 Chemistry Sample Paper 1

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Board EXAMINATION 2025-2026

Class: 12 | Subject: Chemistry (043) | Set: 2

Max Marks: 70 | Time: 3 Hours

Date: 13/12/2025

General Instructions:

• This question paper contains 33 questions. All 33 questions are compulsory.
• The question paper is divided into five sections - Section A, B, C, D and E.
• Section A: Q.1 to Q.16 are multiple choice type questions. Each question carries 1 mark.
• Section B: Q.17 to Q.21 are very short answer type questions. Each question carries 2 marks.
• Section C: Q.22 to Q.28 are short answer type questions. Each question carries 3 marks.
• Section D: Q.29 and Q.30 are case based questions. Each question carries 4 marks.
• Section E: Q.31 to Q.33 are long answer type questions. Each question carries 5 marks.
• There is no overall choice given in the question paper.
• Use of calculators is not allowed.

Section A (1 Mark Each)

1. The correct increasing order of boiling points of the compounds: Pentan-1-ol(a), n-butane(b), pentanal(c), ethoxy ethane(d)

1. \( b < d < c < a \)
2. \( a < b < c < d \)
3. \( c < a < d < b \)
4. \( d < a < b < c \)

2. Identify the reagent which can be used to distinguish ethanol from propanol using:

1. \( NaOH/I_2 \)
2. Lucas reagent
3. Na
4. \( FeCl_3 \)

3. The oxidation state of Cr in \( [Cr(NH_{3})_{4}Cl_{2}]^{+} \) is

1. +3
2. +2
3. +1
4. 0

4. Benzenediazonium chloride can be converted to nitro benzene using

1. \( \text{con.H}_2SO_4/\text{con. HNO}_3 \)
2. \( HBF_{4}/Cu, NaNO_{2}/\text{heat} \)
3. \( HBF_{4}/NH_{3} \)
4. \( HBF_4/HCN/H_3O^+ \)

5. Which of the following salt will have same value of vant Hoff's factor(i) as that of \( K_{4}[Fe(CN)_{6}] \)?

1. \( Al_{2}(SO_{4})_{3} \)
2. \( NaCl \)
3. \( Al(NO_{3})_{3} \)
4. \( Na_{2}SO_{4} \)

6. Arrange the following compounds in the decreasing order of acidity: Phenol, o-nitrophenol, o-cresol, and ethanol.

1. \( \text{o-nitrophenol} > \text{Phenol} > \text{o-cresol} > \text{Ethanol} \)
2. \( \text{Ethanol} > \text{Phenol} > \text{o-cresol} > \text{o-nitrophenol} \)
3. \( \text{o-cresol} > \text{Phenol} > \text{Ethanol} > \text{o-nitrophenol} \)
4. \( \text{Phenol} > \text{o-nitrophenol} > \text{o-cresol} > \text{Ethanol} \)

7. The reaction of toluene with \( Cl_{2} \) in the presence of \( FeCl_3 \) gives X and in the presence of light gives Y. Identify X and Y.

1. X - benzal chloride, Y - o-chlorotoluene
2. X - chlorotoluene, Y - p-chlorotoluene
3. X - o-and p-chlorotoluene, Y - benzyl chloride
4. X - benzyl chloride, Y - o-and p-chlorotoluene

8. Cellulose is a polymer of

1. \( \beta \)-D glucose
2. \( \alpha \)-D glucose
3. \( \beta \)-D fructose
4. \( \alpha \)-D fructose

9. When \( KMnO_{4} \) solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because

1. \( CO_{2} \) is formed as the product
2. reaction is exothermic
3. \( Mn^{2+} \) acts as auto catalyst
4. \( MnO_{4}^{-} \) catalyses the reaction

10. Which of the following expressions gives the limiting molar conductivity of ammonium hydroxide?

1. \( \lambda^{0}_{m(NH_4OH)} + \lambda^{0}_{m(NH_4Cl)} - \lambda^{0}_{m(HCl)} \)
2. \( \lambda^{0}_{m(NH_4Cl)} + \lambda^{0}_{m(NaOH)} - \lambda^{0}_{m(NaCl)} \)
3. \( \lambda^{0}_{m(NH_4Cl)} + \lambda^{0}_{m(NaCl)} - \lambda^{0}_{m(NaOH)} \)
4. \( \lambda^{0}_{m(NaOH)} + \lambda^{0}_{m(NaCl)} - \lambda^{0}_{m(NH_4Cl)} \)

11. An organic compound (A) with the molecular formula \( C_8H_8O \) gives a positive 2,4-DNP test, a positive iodoform test but a negative Tollens' test. The compound A is:

1. Benzaldehyde
2. Acetophenone
3. Phenylacetaldehyde
4. Methyl benzoate

12. Biphenyl is prepared by the reaction of aryl chlorides in the presence of Na/ dry ether. This reaction is known as:

1. Wurtz reaction
2. Sandmeyer reaction
3. Finkelstein reaction
4. Fitting reaction

For questions 13 to 16, select the most appropriate answer from the options given below:

• A. Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation of Assertion (A).
• B. Both Assertion (A) and Reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).
• C. Assertion (A) is correct, but Reason (R) is incorrect.
• D. Both Assertion (A) is incorrect and Reason (R) is correct.

13. Assertion: The decreasing order of basic character of amines in gaseous phase is \( 3^{0} > 2^{0} > 1^{0} > NH_{3} \)
Reason: Amines act as Lewis bases as they have an unshared pair of electrons on the nitrogen atom.

14. Assertion: The solubility of gases in liquids decreases with rise in temperature.
Reason: The process of dissolution is similar to condensation and dissolution is an exothermic process.

15. Assertion: B group vitamins and vitamin C must be taken regularly in the diet.
Reason: These vitamins are fat-soluble, so they cannot be stored in the body for long periods.

16. Assertion: For measuring the resistance of an ionic solution, an AC source is used.
Reason: A DC source would cause electrolysis, leading to changes in the concentration of the ionic solution, which affects the resistance measurement.

Section B (2 Marks Each)

17. (i) State Raoult's law for a solution of volatile liquids.
(ii) Aquatic animals are more comfortable in cold water than in warm water.

OR

(i) State Henry's law for a solution of gas in a liquid.
(ii) The elevation of boiling point of 1M KCl solution is nearly double than that of 1M sugar solution.

18. (i) Identify the order of the reaction for the hydrogenation of ethene and write the unit of the rate constant, k for the same reaction.
(ii) Identify the slope and the y- intercept of the graph, when \( \ln[R] \) is plotted against time, t for first order reaction.

19. Effect the following conversions.
(i) benzenediazonium chloride to toluene
(ii) chloro ethane to ethanamine

20. Write the IUPAC name of the complex, give the d-orbital occupation and the co-ordination number of the central metal ion of the complex, \( K_{3}[Co(C_{2}O_{4})_{3}] \).

21. The following is not an appropriate reaction for the preparation of t-butyl ethyl ether,

\( C_2H_5ONa + (CH_3)_3 - C - Cl \longrightarrow (CH_3)_3C - O - C_2H_5 \)

(i) What would be the major product of this reaction and why do you get that product?
(ii) Write a suitable reaction for the preparation of t-butylethyl ether.

Section C (3 Marks Each)

22. (i) List any two characteristics of an ideal solution.
(ii) Determine the osmotic pressure of a solution prepared by dissolving 0.025g of \( K_{2}SO_{4} \) in 2 litre of water at \( 25^{0}C \), assuming that it is completely dissociated.
\( (R = 0.0821 \, L \, atm \, K^{-1} \, mol^{-1}) \)

23. Calculate the EMF of the voltaic cell, \( Cu/Cu^{2+}_{(0.1M)}//Ag^{+}_{(0.001M)}/Ag \) set up at \( 25^{0}C \) using Nernst equation, given \( {E^{0}}_{Cu^{2+}/Cu} = 0.34V \), \( {E^{0}}_{Ag^{+}/Ag} = 0.80V \).

24. Account for the following:
(i) Aryl halides are extremely less reactive towards nucleophilic substitution reaction.
(ii) Grignard reagents should be prepared under anhydrous conditions.
(iii) There is an inversion of configuration when an optically active compound undergoes nucleophilic substitution by \( S_{N}2 \).

25. (i) How do you prepare \( KMnO_{4} \) from \( MnO_{2} \)?
(ii) Out of \( Cr^{3+} \) and \( Mn^{3+} \) which is a stronger oxidizing agent and why?

26. Write the chemical equation for the reaction:
(i) methoxy benzene is treated with HI
(ii) acetaldehyde is treated with \( CH_{3}MgCl \), followed by hydrolysis
(iii) sodium phenoxide is treated with \( CO_{2} \), followed by hydrolysis

27. (i) Write the aldol condensation product obtained when propanal is treated with dil.NaOH giving the necessary equation.
(ii) Write a note on (a) Cannizaro reaction (b) Etard reaction

28. (i) Many \( Cu(I) \) compounds are unstable in aqueous solution and undergo disproportionation. Why?
(ii) Calculate the spin only magnetic moment of \( M^{2+} \) ion \( (Z=27) \).
(iii) Complete and balance the following equation, \( MnO_{4}^{-} + Fe^{2+} \rightarrow Mn^{2+} + Fe^{3+} \)

Section D (Case Based - 4 Marks Each)

29. Electroplating is a common application of electrolysis, used to deposit a thin, aesthetically pleasing and corrosion-resistant layer of a metal onto a surface. A student decides to silver-plate a brass spoon in their laboratory setup. They use an electrolytic cell containing an aqueous solution of silver nitrate (\( AgNO_3 \)), a pure silver rod as the anode, and the brass spoon as the cathode. The reaction at the cathode is:

\( Ag^{+}(aq) + e^{-} \rightarrow Ag_{(s)} \)

The student operates the cell with a constant current for a specific duration and records the data in the table below:

Parameter	Value	Unit
Current (I)	1.5	A
Time (t)	20.0	Minutes
Molar Mass of Silver (Ag)	108.0	g/mol
Faraday Constant (F)	96500	C/mol
Initial Mass of Spoon	50.0	g

Answer the following questions based on the experimental setup and provided data:

(i) State Faraday's first law of electrolysis. (1 Mark)
(ii) Calculate the total quantity of electricity passed through the electrolytic cell in Coulombs. (1 Mark)
(iii) Calculate the mass of silver (Ag) deposited on the spoon during the experiment.

OR

(iii) If a current of 0.5 ampere flows through a metallic wire for 2 hours, then how many electrons would flow through the wire? (2 Marks)

30. Several theories have been offered to explain the nature of coordination compound bonding. The Valence Bond Theory was created to use quantum physics to explain chemical bonding. This theory is primarily concerned with the formation of individual bonds from the atomic orbitals of the atoms involved in the formation of a molecule. Crystal Field Theory is one of the most widely accepted theories for explaining coordination complex bonding. Hans Bethe came up with the idea. It treated atoms as hard spheres, and their interaction is purely electrostatic. Crystal field theory satisfactorily explains several of the features of complexes that could not be addressed by valence bond theory. The crystal field splitting depends on the field produced by the ligand and the charge on the metal ion. An experimentally determined series based on the absorption of light by coordination compounds with different ligands known as spectrochemical series has been proposed.

Spectrochemical series arranges ligands in order of their field strength as:
\( I^{-} < Br^{-} < Cl^{-} < SCN^{-} < F^{-} < OH^{-} < C_{2}{O_{4}}^{2-} < H_{2}O < NCS^{-} < EDTA^{4-} < NH_3 < en < CN^{-} < CO \)

Filling of d-orbitals takes place in the following manner; the first three electrons are arranged in \( t_{2g} \) level as per the Hund's rule. The fourth electron can either enter into the \( t_{2g} \) level giving a configuration of \( t_{2g}^{4}e_{g}^{0} \) or can enter the \( e_{g} \) orbital giving a configuration of \( t_{2g}^{3}e_{g}^{1} \). This depends on two parameters magnitude of crystal field splitting, \( \Delta_o \) and pairing energy, P.

Answer the following questions:

(i) What are the factors that decide crystal field splitting in a complex?
(ii) On the basis of CFT, identify whether the complex, \( [Fe(CN)_{6}]^{4-} \) is coloured or not, giving suitable explanation.
(iii) Using VBT, explain the geometry and magnetic behaviour of the complex, \( [Cr(NH_{3})_{6}]^{3+} \).

OR

(iii) \( [NiCl_{4}]^{2-} \) is paramagnetic while \( [Ni(CO)_{4}] \) is diamagnetic though both are tetrahedral. Why?

Section E (Long Answer - 5 Marks Each)

31. Attempt either A or B

A. Answer the following questions:

1. Write a chemical test to differentiate between ethanal and benzaldehyde.
2. Write the chemical equation for the following reaction:
   (a) ethanal is treated with hydrazine
   (b) ethanoyl chloride is treated Hydrogen/Nickel/\( BaSO_4 \).
3. Aldehydes readily undergo nucleophilic addition reaction when compared to ketones. Why?
4. How do you obtain propene from propanone?

B. Answer the following questions:

1. Write a chemical test to differentiate between pentan-2-one and pentan-3-one.
2. Write the structure of the products in the following reactions and also write the name of the reactions of the following reactions:
   (a) \( CH_3-CH_2-CHO + Zn-Hg/HCl \)
   (b) \( CH_3-CH_2-COOH + Br_2 / \text{red phosphorous} \)
3. An organic compound with the molecular formula \( C_{9}H_{10}O(A) \) forms 2,4-DNP derivative, reduces Tollen's reagent and undergoes Cannizzaro reaction. On vigorous oxidation it gives 1,2- benzenedicarboxylic acid. Identify the compound giving suitable justification and also write the equation for the oxidation reaction.

32. Attempt either A or B

A. Answer the following questions:

1. Give any two points of structural differences between DNA and RNA.
2. Draw the Fischer projection formula of D (+) glucose.
3. Why is sucrose non-reducing in nature though its monomers are reducing in nature?
4. What do you mean by denaturation of protein?

B. Answer the following questions:

1. Give any two points of differences between fibrous and globular protein.
2. Draw the structure of \( \alpha \)-D - (+) Glucopyranose.
3. Write the chemical reaction which indicates that glucose contains aldehyde as its carbonyl group.
4. What are essential amino acids and give two examples?

33. Attempt either A or B

A. Answer the following questions:

1. The rate of a reaction quadruples when the temperature changes from 293K to 313K. Calculate the energy of activation of the reaction assuming it does not change with temperature.
2. Give any two characteristics of a catalyst.
3. Show that in a first order reaction, time required for completion of 99.9% is 10 times of half-life of the reaction.

B. Answer the following questions:

1. The half-life for radioactive decay of \( {}^{14}C \) is 5730 years. An archaeological artefact containing wood had only 80% of the \( {}^{14}C \) found in a living tree. Estimate the age of the tree.
2. Identify the order of decomposition reaction of ammonia on a hot platinum surface and derive the expression for half-life of the reaction.
3. Give any two points of differences between order and molecularity.

(Given: \( R = 8.314 JK^{-1}mol^{-1} \), \( \log 2 = 0.3010 \), \( \log 3 = 0.4771 \))