Class 12 Pre-Board Sample Paper 2025 Chemistry

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Pre-Board Exam 2025 Sample Question Paper

Class 12 Chemistry
General Instructions:
Read the following instructions carefully.
a) There are 33 questions in this question paper with internal choice.
b) SECTION A consists of 16 multiple-choice questions carrying 1 mark each.
c) SECTION B consists of 5 very short answer questions carrying 2 marks each.
d) SECTION C consists of 7 short answer questions carrying 3 marks each.
e) SECTION D consists of 2 case- based questions carrying 4 marks each.
f) SECTION E consists of 3 long answer questions carrying 5 marks each.
g) All questions are compulsory.
h) Use of log tables and calculators is not allowed
SECTION A
The following questions are multiple-choice questions with one correct answer. Each
question carries 1 mark. There is no internal choice in this section.
1 Which of the following lanthanoids show +2 oxidation state besides the characteristic 1
oxidation state +3 of lanthanoids?
(a) Ce (b) Eu (c) Lu (d) Ho
2 The formula of the complex tris(ethan-1,2 diamine)cobalt(III) Sulphate is 1
(a)[Co(en)3]SO4 (b)[Co(en)3 SO4]
(c)[Co(en)3]2(SO4)3 (d)[Co(en)3](SO4)3
3 The compounds [Co(SO4)(NH3)5]Br and [Co(SO4)(NH3)5]Cl represents 1
(a) Linkage isomerism (b) No isomerism
(c) Ionisation isomerism (d) Coordination isomerism
4 Hoffmann Bromamide Degradation reaction is shown by 1
(a) ArNH2 (b) ArCONH2 (c) ArNO2 (d) ArCH2NH2

5 For NaCl the value of Van’t Hoff factor is 1
(a) 0 ( b) 1 (c) >1 (d) <1

6 The magnetic moment is associated with its spin angular momentum and orbital angular 1
momentum. Spin only magnetic moment value of Mn2+ ion is
(a) 5.87 B.M. (b) 5.92 B.M. (c) 3.47 B.M (d) 4.57 B.M
7 The difference between the electrode potentials of two electrodes when no current is drawn 1
through the cell is called
(a) Cell potential (b) Cell emf (c) Potential difference (d) Cell voltage
8 Charge carried by 1 mole of electrons is 1
(a) 6.023 × 1023 coulomb 4
(b) 9.65 × 10 coulomb
–19 19
(c) 1.6 × 10 coulomb (d) 6.28 × 10 coulomb
9 Which reagent will you use for the following reaction? 1

CH3CH2CH2CH3 → CH3CH2CH2CH2Cl + CH3CH2CHClCH3
(a) Cl2/UV light (b) NaCl + H2SO4
(c) Cl2 gas in presence of Fe in dark (d) Cl2 gas in dark
10 Phenol is less acidic than 1
(a) Ethanol (b) o-nitrophenol (c) o-methylphenol (d) o-methoxyphenol

11 Which out of the following reactions needs no α-H atom to get started? 1
(a) Etard reaction (b) Cannizaro’s reaction
(c) Aldol condensation (d) HVZ reaction
12 In the reaction, A + 2B --🡪 6C + 2D, if the initial rate – d [A]/dt at t = 0 is 2.6 × 10–2 M sec–1, 1
what will be the value of – d [B]/dt at t = 0?
(a) 8.5 × 10–2 M sec–1 (b)2.5 × 10–2 M sec–1
(c) 5.2 × 10 M sec (d)7.5 × 10 M sec–1
–2 –1 –2

In the Following questions a statement of Assertion(A) is followed by a statement of
Reason(R). Select the most appropriate answer from the options given below:
(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.
13 Assertion (A):Sucrose is a non-reducing sugar. 1
Reason (R):In sucrose, the aldehydic group of glucose and ketonic group of fructose are
not free.

14 Assertion (A): D-(+)-Glucose is dextrorotatory in nature. 1
Reason (R): D-(+) Glucose rotates the plane polarised light in clockwise direction.

15 Assertion (A): Aromatic 1o amine can be prepared by Gabriel phthalamide synthesis. 1
Reason (R): Primary Alkylhalide undergoes nucleophilic substitution reaction with anion
formed by phthalamide.
16 Assertion (A): Nitration of aniline can be conventionally done by protecting the amino 1
group by acetylation.
Reason (R):Acetylation increases the electron density in benzene ring.

SECTION B
This section contains 5 questions with internal choice in one question. The following
questions are very short answer type and carry 02 marks each.

17 Write the reaction involve in recharging the lead storage battery. 2

18 Calculate the emf of the cell in which the following reaction takes place: 2
Ni(s) + 2Ag+ (0.002 M) → Ni2+ (0.160 M) + 2Ag(s)
[Given that Eo cell = 1.05 V, log 2 = 0.301]
19 A metal ion M+ having d4 valence electronic configuration combines with three bidentate 2
ligands to form a complex compound. Assuming Δ0> P:
(i) Name the type of orbital splitting during this complex formation.
ii) Write the electronic configuration of the valence electrons of the metal M+ ion in
terms of t2g and eg.

20 Arrange the following sets of compounds in order of their increasing boiling points:
(a) Pentan-1-ol, butan-1-ol, butan-2-ol, ethanol, propan-1-ol, methanol.

(b) Pentan-1-ol, n-butane, pentanal, ethoxyethane. 2

OR
Explain the mechanism of the acid catalysed hydration of ethene.

21 What happens when D-glucose is treated with the following reagents? 2
(i) HCN (ii) NH2OH

SECTION C
This section contains 7 questions with internal choices in one question. The following
questions are short answer types and carry 3 marks each.
22 The limiting molar conductivity of sodium acetate, sodium chloride and hydrochloric acid 3
◦
are 83, 127 and 426 mho 𝑐𝑚2 𝑚𝑜𝑙-1 at 250 𝐶 respectively. Calculate the limiting molar
conductivity of acetic acid solution.
23 The chemistry of corrosion of iron is essentially an electrochemical phenomenon. Explain 3
the reactions occurring during the corrosion of iron in the atmosphere.

24 How will you convert the following in not more than two steps: 3
(i) Benzoic acid to benzaldehyde
(ii)Acetophenone to benzoic acid
(iii)Ethanoic acid to 2-hydroxyethanoic acid

25 CoSO4Cl.5NH3 exists in two isomeric forms ‘A’ and ‘B’. Isomer ‘A’ reacts with AgNO3 to 3
give white precipitate, but does not react with BaCl2. Isomer ‘B’gives white precipitate with
BaCl2 but does not react with AgNO3. Answer the following questions.
(i) Identify ‘A’ and ‘B’ and write their structural formulas.
(ii)Name the type of isomerism involved.
(iii)Give the IUPAC name of ‘A’ and ‘B’.

26 Give reasons for the following: - 3
) Alcohols are more soluble in water than the hydrocarbon of comparable molecular masses.
(b) Phenoxide ion is more stable than phenol.
(c) Ortho nitro phenol is more acidic than Ortho-methoxyphenol.
OR
Write Short notes on the following reactions
(a) Williamson Synthesis
) Reimer Tiemann reaction
) Oxidation of phenol

27 Arrange the following: 3
(i) CH3NH2, (CH3)2NH, NH3, (CH3)3N [basic strength in gaseous phase] (In decreasing
order)
(ii) C2H5NH2, C6H5NH2, NH3, C6H5CH2NH2 and (C2H5)2NH [basic strength] ] (In
increasing order)
(iii) C6H5NH2, C6H5N(CH3)2, (C2H5)2NH and CH3NH2 [basic strength] ] (In
increasing order)
28 Give answer for the following: 3
(i) Give one structural difference between amylose and amylopectin
(ii) Name the protein and its shape present in the oxygen carrier in the human body.
(iii)What type of linkage is present in proteins?

SECTION D
The following questions are case-based questions. Each question has an internal choice and
carries 4 (1+1+2) marks each. Read the passage carefully and answer the questions that
follow.

29 Read the passage given below and answer the following questions:
Aldehydes and ketones having acetyl group are oxidised by sodium hypohalate (NaOX)
or halogen and alkali (X2 + OH-) to corresponding sodium salt having one carbon atoms
less than the carbonyl compound and give a haloform.
Sodium hypoiodite (NaOI) when treated with compounds containing CH3CO - group 4
gives yellow precipitate of iodoform. Haloform reaction does not affect a carbon-carbon
double bond present in the compound.
i) Why the methanal is more reactive towards nucleophilic substitution reaction than
ethanal.
(ii) Write the structure of pentane -2- one.
OR
Write the common name of 1,1,1trichloro ethanal.
(iii) How can you distinguish between Acetophenone and benzophenone.

30 Read the passage given below and answer the following questions:
The solubility of gases increases with increase of pressure. William Henry made a 4
systematic investigation of the solubility of a gas in a liquid. According to Henry's law
"the mass of a gas dissolved per unit volume of the solvent at constant temperature is
directly proportional to the pressure of the gas in equilibrium with the solution".
Dalton during the same period also concluded independently that the solubility of a gas
in a liquid solution depends upon the partial pressure of the gas. If we use the mole
fraction of gas in the solution as a measure of its solubility, then Henry's law can be
modified as "the partial pressure of the gas in the vapour phase is directly proportional
to the mole fraction of the gas in the solution':
(i) Why the aquatic animals feel more comfortable in cold water.
i) How solubility of gas in liquid varies with increasing
temperature.
ii) Write any two applications of henry law.
OR
State Henry’s law for gas in liquid solution. Write the mathematical expression of this
law.

SECTION E

31 Attempt any five of the following-
(a) Why enthalpy of atomisation of transition metals are quite high.
(b) There is a close similarity in physical and chemical properties of the 4d and 5
5d series of the transition elements, Explain.
(c) Why the members in the actinoid series exhibit larger number of oxidation
states than the corresponding members in the lanthanoid series.
9
(d) 𝐶𝑢2+ is stable in aqueous solution inspite of having 3𝑑 configuration.
Why?
(e) The E° values of Mn and Zn is more negative. Give reason.

(f) The transition metals are generally paramagnetic in nature why?
(g) Scandium is a transition element but Zinc is not. Why?
The following questions are long answer type and carry 5 marks each. Two questions have
an internal choice.

32 (i) Among all the isomers of molecular formula C4H9Br, identify- 5
(a) the one isomer which is optically active.
(b) the one isomer which is highly reactive towards SN2.
(c) the two isomers which give the same product on
dehydrohalogenation with alcoholic KOH.
(ii)Give IUPAC the name of the following organic compounds:

OR
What happens when-
(i) n-butyl chloride is treated with alcoholic KOH,
(ii)bromobenzene is treated with Mg in the presence of dry ether,
(iii)chlorobenzene is subjected to hydrolysis,
(iv)ethyl chloride is treated with aqueous KOH,
(v) methyl bromide is treated with sodium in the presence of dry ether.
33 a)The rate constant for a first order reaction is 60 s–1. How much time will it take to reduce
the initial concentration of the reactant to its 1/16th value? 5
b) Calculate the energy of activation of a reaction for which rate constant becomes
doubles by Increase of 10K temperature from 298K
OR
(a)(i) A reaction is 50% complete in 2 hours and 75% complete in 4 hours. What is the
order of the reaction?
(ii) A first order reaction is 50% completed in 1.26 × 1014 s. How much time would it
take for100% completion?
(iii) The activation energy of a reaction is zero. Will the rate constant depend
upon temperature? Explain.
(b) A reaction is first order in A and second order in B. Write the differential rate equation
and calculate how the rate is affected when
(i) concentration of B is tripled, (ii) concentration of both A and B is doubled.

CHEMISTRY XII
MARKING SCHEME
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

b c b b c b b b a b b c a a d c

Q. Value Point/ Expected Answer Marks
No
.
17 During recharging, electrical energy is supplied to the cell from an external source. The 2
reactions are reverse of those that takes place during discharge.
At cathode: PbSO4 (s) +2e– → Pb(s) + SO 2–(aq)
4
At anode: PbSO4 (s) + 2H2O → PbO2 (s) + 4H+(aq) + SO 2–(aq) + 2e–
4
Overall reaction: PbSO4 (s) + 2H2 O(l) → Pb(s) + PbO2 (s) + 2H2 SO4 (aq)

18 2

19 (i) Octahedral splitting will takes place. 1
4
(ii)As Δ0 > P pairing will occur in the t2g orbitals and eg orbitals will remain vacant. t2g 1
eg0
20 (a) Methanol, ethanol, propan-1-ol, butan-2-ol, butan-1-ol, pentan-1-ol. 1
(b)n-Butane, ethoxyethane, pentanal and pentan-1-ol. 1
O
R
+ +
Step 1: Protonation of ethene to form carbocation by electrophilic attack of 𝐻 𝑂 .
3
2

21 (i) Cyanohydrin, (ii)Oxime 1
1

22 3

23 3

24

25 (i) A - [Co(NH3)5SO4]Cl B - [Co(NH3)5Cl]SO4 1
(ii) Ionisation isomerism 1
(iii) (A), Pentaamminesulphatocobalt (III) chloride 1
(B), Pentaamminechloridocobalt (III) sulphate.

26 a)Alcohols have hydrogen bonding whereas hydrocarbons have weak vander waal‘s force of 1
attraction.
(b) due to +M or +R effect in phenoxide ion. 1
c)Ortho nitrophenol is more acidic due to electron withdrawing effect of nitro group which
facilitates release of proton. 1

OR
(a) R-X + R-ONa → ROR + NaX (in presence of dry ether)
(b) C6H50H + CHCl3 + KOH → Salicyldehyde + KCl + H2O 1
(c) C6H5OH+ Na2Cr2O7/H2SO4 → benzoquinone 1
1

27 (i) (CH3)3N > (CH3)2NH >CH3NH2> NH3 1
(ii)C6H5NH2< NH3< C6H5CH2NH2< C2H5NH2< (C2H5)2NH
1
(iii)C6H5NH2< C6H5N(CH3)2< CH3NH2< (C2H5)2NH
1
28 (i) Amylose is a long unbranched chain polymer of α-D(+) glucose. Amylopectin is a branched 1
chain polymer of α-D(+) glucose. 1
(ii) Globular protein (haemoglobin) and its shape are spherical. 1
(iii) Peptide linkage

29 (i) due to less steric hindrance in methanal. 1
(ii)Correct structure. 1
OR 2
(i) Chloral
iodoform test and correct equation.

30 i) The amount of dissolved oxygen in water decreases with rise in the water's temperature. 1
Cold water has more dissolved oxygen per unit area than warm water. This the reason why
aquatic animals are more comfortable in cold water than warm water.
ii) Solubility of gas in liquid 1
decreases. (iii)Any two applications
OR 2
iii) According to Henry's law "the mass of a gas dissolved per unit volume of the solvent at
constant temperature is directly proportional to the pressure of the gas in equilibrium with the
solution".
P=KHX
31 ) This is because transition metals have strong metallic bonds as they have large number of
unpaired electrons.
) This is because 5d and 4d-series elements have virtually the same atomic and ionic radii due to 1x5
lanthanoid contraction. =5
(c) due to the fact that the 5f, 6d and 7s levels are of comparable energies.
2+
(d) The high energy to transform Cu(s) to Cu (aq) is balanced by its hydration enthalpy.
2+ 10
(e) The stability of the half-filled d sub-shell in Mn and the completely filled Zn
2+
configuration in Zn are related to their more negative E° V values.
due to incomplete d orbitals and presence of unpaired electron.
(g)Because of fully filled d orbitals in zinc.
32 2

3

1x3

OR 2x1

33 1
1
1

2

1x5

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