SAMPLE PAPER (2025-26)
CHEMISTRY THEORY (043) — Class XII
Max. Marks: 70 Time: 3 hours
GENERAL INSTRUCTIONS
Read the following instructions carefully
There are 33 questions in this question paper with internal choices.
SECTION A: 16 multiple-choice questions carrying 1 mark each.
SECTION B: 5 very short answer questions carrying 2 marks each.
SECTION C: 7 short answer questions carrying 3 marks each.
SECTION D: 2 case-based/source-based questions, each carrying 4 marks (with sub-parts).
SECTION E: 3 long answer questions carrying 5 marks each.
All questions are compulsory.
Use of log tables and calculators is not allowed.
SECTION A
The following are multiple-choice questions. Each question carries 1 mark. Only one is correct for each.
1. A solution of sodium thiosulphate is mixed with dilute hydrochloric acid. Which observation is correct?
a. Evolution of brown gas
b. Formation of yellow precipitate
c. Blue coloration
d. Formation of green solid
2. Which compound shows the highest boiling point?
a. CH3Cl
b. CH3Br
c. CH3F
d. CH3I
3. Match the transition elements to their configuration:
Column I
(i) [Ar] 3d104s1
(ii) [Kr] 4d105s1
(iii) [Xe] 4f145d106s1
Column II
(A) Cu
(B) Ag
(C) Au
a. (i)-(A), (ii)-(B), (iii)-(C)
b. (i)-(B), (ii)-(C), (iii)-(A)
c. (i)-(C), (ii)-(A), (iii)-(B)
d. (i)-(A), (ii)-(C), (iii)-(B)
4. Among the following, which compound does not react with Fehling's solution?
a. Glucose
b. Fructose
c. Sucrose
d. Maltose
5. The half-life of a zero order reaction with initial concentration 0.1 mol/L and rate constant 2 × 10–3 mol L–1s–1 is
a. 10 s
b. 20 s
c. 50 s
d. 100 s
6. Which is the product formed when propanamide is treated with Br2 in NaOH?
a. Ethylamine
b. Propylamine
c. Aniline
d. Acetanilide
7. What is the oxidation state of Mn in [MnO4]–?
a. +2
b. +4
c. +6
d. +7
8. Which polysaccharide contains only α-D-glucose units?
a. Cellulose
b. Starch
c. Glycogen
d. Chitin
9. Arrange the following ions in increasing order of paramagnetism: Fe3+, Mn2+, Cr3+, Ni2+
a. Cr3+ < Fe3+ < Ni2+ < Mn2+
b. Fe3+ < Cr3+ < Ni2+ < Mn2+
c. Ni2+ < Cr3+ < Fe3+ < Mn2+
d. Cr3+ < Ni2+ < Fe3+ < Mn2+
10. For a first order reaction, the rate constant k = 0.693 × 10–3 s–1. What is the half-life?
a. 500 s
b. 1000 s
c. 100 s
d. 10 s
11. The compound which gives white precipitate with AgNO3 is:
a. Ethyl bromide
b. Methyl chloride
c. Benzyl chloride
d. Propyl iodide
12. Which compound reacts with hydroxylamine to give an oxime?
a. Ethanal
b. Ethanoic acid
c. Ethanol
d. Ethyl acetate
13. Assertion (A): K2Cr2O7 acts as a strong oxidising agent in acidic medium.
Reason (R): The reduction potential of Cr2O72– / Cr3+ is high in acidic medium.
a. Both A and R are true; R explains A
b. Both A and R are true; R does not explain A
c. A true; R false
d. A false; R true
14. Assertion (A): For strong electrolytes, molar conductivity increases slightly with dilution.
Reason (R): The degree of dissociation increases with dilution for weak electrolytes, not strong ones.
a. Both A and R are true; R explains A
b. Both A and R are true; R does not explain A
c. A true; R false
d. A false; R true
15. Assertion (A): Fructose does not form an addition product with NaHSO3. Reason (R): Fructose mostly exists in a five-membered ring structure.
a. Both A and R are true; R explains A
b. Both A and R are true; R does not explain A
c. A true; R false
d. A false; R true
16. Assertion (A): The half-life for a zero order reaction depends on initial concentration.
Reason (R): For a zero order reaction, Rate = k.
a. Both A and R are true; R explains A
b. Both A and R are true; R does not explain A
c. A true; R false
d. A false; R true
SECTION B
This section contains 5 questions with internal choice in one question. The following questions are very short answer type and carry 2 marks each.
17. a) State Henry's law.
b) How does increasing temperature affect the solubility of gases in liquids?
18. a) Write IUPAC name: [Co(NH3)5Cl]Cl2.
b) Name the central metal in Vitamin B12.
19. a) Represent the cell: Zn(s) | Zn2+(aq) || Ag+(aq) | Ag(s).
b) Name the charge carriers in the salt bridge.
20. Complete (any two):
a) 2-bromopropane + KOH (alc) →
b) Benzaldehyde + NH2OH →
c) Propene + HBr (peroxide) →
21. What type of carbonyl group is present in fructose? Give a test to confirm its presence.
SECTION C
This section contains 7 questions with internal choice in one question. The following questions are short answer type and carry 3 marks each.
22. a) Write electrode reactions for electrolysis of CuSO4 using Pt electrodes.
22. b) What happens if Cu electrodes are used instead?
23. a. Give reason: Lowest oxide of transition metals is basic, highest is acidic.
b. Why is Zn not considered a typical transition element?
c. Why does Sc show only +3 oxidation state?
24. a) What happens when acetone is treated with 2,4-dinitrophenylhydrazine?
b) Aldol condensation—what type of compounds does not undergo it?
c) Distinguish between acetone and acetic acid (one test).
25. a) Draw all dipeptides formed by valine and glycine.
b) Differentiate between globular and fibrous proteins: give examples each.
26. a) Identify dehydration products of butan-2-ol at 140°C and 180°C and mechanisms.
b) Write equations.
27. Among isomeric C4H9Br, which forms carbocation fastest via SN1 and why? Write mechanism.
28. E0(Zn2+/Zn) = -0.76 V, E0(Ag+/Ag) = +0.80 V. Calculate standard emf for Zn-Ag cell. Will Zn reduce Ag+?
SECTION D
The following questions are case-based questions. Each question has an internal choice and carries 4 (2+1+1) marks each. Read the passage carefully and answer the questions that follow.
29. A reaction A + 2B → Product shows a rate = k[A][B]2.
a) Predict the order.
b) What happens if [B] is doubled?
c) What is the unit of k?
d) Choose a possible mechanism and justify.
30. The basicity of substituted amines is influenced by electron-withdrawing or donating groups. pKa + pKb = 14. The following data is given for pKa values:
–CH3: 10.6; –NO2: 8.0; –OCH3: 10.0
a) Plot pKa vs basic strength.
b) How does presence of –NO2 affect basicity?
c) What is pKb if pKa is 8.0?
d) Which is a stronger base: ethylamine or p-nitroaniline?
SECTION E
The following questions are long answer types and carry 5 marks each. All questions have an internal choice.
31. a) A green compound A is used in qualitative analysis: it reacts with dilute H2SO4 and forms a blue solution and a brown gas. Identify A, write equations.
b) Discuss d2sp3 and sp3d2 hybridisation in coordination complexes. Draw diagrams.
32. a) Why is pyridine used in the reaction of alcohol with acyl chloride?
b) Arrange: butan-1-ol, 2-methylpropan-2-ol, butan-2-ol, 2-methylpropan-1-ol — in order of acidity. Explain.
c) Convert benzene to m-nitroacetophenone.
33. a) Which of these: 1M NaCl or 1M glucose has higher depression in freezing point? Why?
b) The osmotic pressure of a cane sugar solution is 2.5 atm at 300 K; what will it be after fivefold dilution?
c) Suggest 2 ways to decrease osmotic pressure of a solution without changing its volume.
ANSWER
SECTION A
| Question No. | Answer | Explanation |
|---|---|---|
| 1 | b. Formation of yellow precipitate | Sodium thiosulphate + HCl produces yellow sulfur precipitate. |
| 2 | d. CH3I | Highest boiling point due to greater molecular mass and van der Waals forces. |
| 3 | a. (i)-(A), (ii)-(B), (iii)-(C) | Configurations match Cu, Ag, Au respectively. |
| 4 | c. Sucrose | Non-reducing sugar; no reaction with Fehling’s solution. |
| 5 | a. 10 s | Zero order half-life approx.; (t1/2 = 0.693/2k) |
| 6 | a. Ethylamine | Hofmann bromamide reaction product. |
| 7 | d. +7 | Mn in permanganate ion has +7 oxidation state. |
| 8 | b. Starch | Polysaccharide of only α-D-glucose units. |
| 9 | d. Cr3+ < Ni2+ < Fe3+ < Mn2+ | Increasing order based on number of unpaired electrons. |
| 10 | b. 1000 s | First order half-life (t1/2 = 0.693/k) |
| 11 | c. Benzyl chloride | Produces white AgCl precipitate with AgNO3. |
| 12 | a. Ethanal | Forms oxime on reaction with hydroxylamine. |
| 13 | a. Both A and R are true; R explains A | K2Cr2O7 is strong oxidizing agent due to high reduction potential in acid. |
| 14 | a. Both A and R are true; R explains A | Strong electrolytes mostly dissociated; conductivity changes slightly on dilution. |
| 15 | b. Both A and R are true; R does not explain A | Fructose mostly in 5-membered ring; no NaHSO3 addition but different reason. |
| 16 | c. A true; R false | Half-life for zero order depends on concentration; rate = k is not reason. |
SECTION B
17(a): Henry's Law states that at a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid.
17(b): Increasing temperature decreases the solubility of gases in liquids because dissolution of gases is generally exothermic.
18(a): The IUPAC name for [Co(NH3)5Cl]Cl2 is pentaamminechloridocobalt(III) chloride.
18(b): The central metal in Vitamin B12 is cobalt (Co).
19(a): Cell representation is: Zn(s) | Zn2+(aq) || Ag+(aq) | Ag(s), where double vertical lines denote the salt bridge.
19(b): Charge carriers in the salt bridge are mobile ions.
20(a): CH3-CH(Br)-CH3 + KOH (alc) → CH3-CH=CH3 + KBr + H2O
20(b): C6H5CHO + NH2OH → C6H5CH=NOH + H2O
20(c): CH3-CH=CH3 + HBr (peroxide) → CH2(Br)-CH2-CH3
21: Fructose contains a ketonic carbonyl group.
Tests: The presence of a ketone group in fructose can be confirmed by tests such as Seliwanoff's test (positive for ketoses) or by reaction with resorcinol and hydrochloric acid, which gives a cherry-red color.
SECTION C
22(a): Cathode Reaction: Cu2+ + 2e− → Cu.
Anode Reaction: 2H2O → O2 + 4H+ + 4e−.
Overall: CuSO4 dissociates to Cu2+ and SO4-2, Cu2+ reduced at cathode, H2O oxidized at anode.
22(b): Cathode Reaction: Cu2+ + 2e− → Cu.
Anode Reaction: Cu → Cu2+ + 2e−
Net effect: No change in Cu2+ concentration; mass transfer of copper from anode to cathode.
23(a): Lowest oxides are basic due to low oxidation state and ionic character; highest oxides are acidic due to high oxidation state and covalent character, which increases acidity.
23(b): Zn is not considered a typical transition element because its 3d orbital is fully filled (3d10), and neither atom nor ion has partially filled d-orbitals.
23(c): Sc shows only +3 oxidation state; loss of three electrons gives stable noble gas configuration ([Ar]), and higher/lower states are not favored.
24(a): Acetone reacts with 2,4-dinitrophenylhydrazine to give acetone 2,4-dinitrophenylhydrazone (yellow/orange ppt.).
24(b): Compounds without α-hydrogen, like benzaldehyde and formaldehyde, do not undergo aldol condensation.
24(c): Acetone and acetic acid can be distinguish by Iodoform test. Acetone gives yellow ppt. of iodoform while acetic acid does not.
25(a): Dipeptides from valine (Val) and glycine (Gly): Val-Gly and Gly-Val (both N–C combinations possible).
25(b): Globular proteins: Spherical, soluble; e.g., hemoglobin, albumin.
Fibrous proteins: Long, insoluble; e.g., collagen, keratin.
26(a): 140°C (with conc. H2SO4): Butyl ether (symmetrical ether, via bimolecular mechanism/SN2).
180°C (conc. H2SO4): But-2-ene (alkene via E1 elimination).
Mechanisms: 140°C—bimolecular dehydration (ether formation); 180°C—acid-catalyzed elimination (alkene formation).
26(b): At 140°C: 2CH3CH(OH)CH2CH3 ---conc. H2SO4 → CH3CH2CH(OCH2CH3) + H2O
At 180°C: CH3CH(OH)CH2CH3 ---conc. H2SO4 → CH3CH=CHCH3 + H2O
27: tert-Butyl bromide (CH3)3C-Br forms carbocation fastest via SN1 due to high stability of tertiary carbocation.
Mechanism: Ionization forms ( CH3)3C+ and Br⁻; nucleophile attacks the carbocation.
28: E∘cell = E∘cathode − E∘anode
or, E∘cell = 0.80 V (Ag/Ag+) − (−0.76 V (Zn2+/Zn)) = 1.56 V.
Yes, Zn will reduce Ag⁺ because E∘cell > 0
Reaction is spontaneous.
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