MBOSE Class 12 Question Paper 2026 for Chemistry

FOR MBOSE CLASS 12 EXAM PREPARATION

MBOSE Class 12 2026
Question Paper ·
Chemistry
EXAM YEAR TYPE SUBJECT

MBOSE Class 12 2026 Question Paper Chemistry

Notes · Sample Papers · Previous Year Papers · Mock Tests

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Total No. of Printed Pages—15
HS/XII/SC/Ch/26
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CHEMISTRY

( Theory )

Full Marks : 70

Time : 3 hours
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. for the questions.
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The figures in the margin indicate full marks

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General Instructions : a g
Read the following instructions carefully :
(i) All questions are compulsory.
(ii) Attempt all parts of a question together at one place.
(iii) There are 33 questions in this question paper with
internal choice.

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(iv) Section—A consists of 16 multiple-choice questions
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carrying 1 mark each.

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(v) Section—B consists of 5 short answer-type questions
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(vi) Section—C consists of 7 short answer-type questions
carrying 3 marks each.
(vii) Section—D consists of 2 questions carrying 4 marks each.
(viii) Section—E consists of 3 long answer-type questions
carrying 5 marks each.

/70 [ P.T.O.

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( 2 )

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 to
these questions.

1. The maximum amount of solid solute that can be
dissolved in a specified amount of a given liquid solvent
does not depend upon
(a) temperature
(b) nature of solute
(c) pressure
(d) nature of solvent 1

2. The expression of concentration of solution which is
temperature dependent is
(a) molarity
(b) molality
(c) mole fraction
(d) None of the above 1

3. The influence of temperature on the rate of a reaction
is determined by
(a) Nernst equation
(b) Gibbs-Helmholtz equation
(c) van’t Hoff equation
(d) Arrhenius equation 1

HS/XII/SC/Ch/26/70 [ Contd.

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4. The value of rate constant of a pseudo-first-order
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reaction
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(a) depends on the concentration of reactants present

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in small amount
a
(b) depends on the concentration of reactants present
in excess

(c) is independent of the concentration of the reaction

(d) depends only on temperature 1

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5. The reason of lanthanoid contractionmis.
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g laf -orbital
(a) negligible screening effect of
a
(b) increasing nuclear charge

(c) decreasing nuclear charge

(d) decreasing screening effect 1

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6. The catalytic activity of transition metal’s and their
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m (a) their ability to adopt variable oxidation states lase
compounds is due to

s e g
l a a
ag (b) their chemical activity

(c) their magnetic behaviour

(d) their unfilled d-orbital 1

HS/XII/SC/Ch/26/70 [ P.T.O.

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( 4 )

7. Primary, secondary and tertiary alcohols can be
distinguished by

(a) Hinsberg’s test

(b) Tollen’s reagent

(c) Fehling’s solution

(d) Lucas test 1

8. Phenol is more acidic than ethanol because

(a) ethoxide ion is more stable than phenoxide ion

(b) phenoxide ion is more stable than ethoxide ion

(c) phenol undergoes electrophilic substitution reaction

(d) phenol undergoes protonation easily 1

9. The most suitable reagent for the conversion of
RCH2OH ® RCHO is

(a) KMnO4

(b) K 2Cr2O 7

(c) LiAlH4

(d) PCC (Pyridinium Chlorochromate) 1

HS/XII/SC/Ch/26/70 [ Contd.

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10. The compound among the following which gives both
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iodoform and Fehling’s test is
s e m
(a)
s em
ethanol
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(b) propanone ag
a
(c) butan-2-ol
(d) ethanal 1

11. Aldol condensation does not occur between
(a) two different aldehydes
(b) two different ketones
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(c) an aldehyde and a ketone
(d)
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an aldehyde and an ester 1

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12. Which of the following on heating with aqueous KOH,
produces acetaldehyde? 1
(a) CH 3CH2Cl
(b) CH2Cl CH2Cl
(c) CH 3CHCl2

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(d) CH 3COCl
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13. Which one of the following is used in Friedel-Crafts
s e1m
s e acylation reaction?
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g la (a) Anhy. AlCl 3 a
a (b) Aq. AlCl 3
(c) NH2NH2
(d) NH2OH

HS/XII/SC/Ch/26/70 [ P.T.O.

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( 6 )

14. Which one of the following is the correct statement? 1

(a) Alkyl halides are more reactive than aryl halides
towards nucleophilic substitution reaction

(b) Alkyl halides are less reactive than aryl halides
towards nucleophilic substitution reaction

(c) Nucleophilic substitution reaction proceeds through
carbocation

(d) Aryl halides cannot be prepared by electrophilic
substitution to arenes

15. Which complexes do not show geometrical isomerism? 1

(a) Square planar complexes

(b) Tetrahedral complexes

(c) Octahedral complexes

(d) All of the above

16. Copper sulphate cannot be stored in zinc vessel. This
is because

(a) EMF of the reaction is negative

(b) EMF of the reaction is positive

(c) reduction potential value of Zn is more than Cu

(d) reduction potential value of Cu is negative 1

HS/XII/SC/Ch/26/70 [ Contd.

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m
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c. o ( Marks : 10 ) m .co
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Question Nos. 17 to 21 are very short answer-type questions
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carrying 2 marks each.

17. Either

(a) 10% solution of non-volatile solute in water has
a vapour pressure 740 mm at 373 K. Calculate the
molar mass of the solute. 2

Or
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(b) What mass of ethylene glycol must be added to
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5·5 kg of water to lower the freezing point from
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0 °C to –10 °C? K f for water = 1 × 86 K kg mol -1,
g
molar mass of ethylene a
glycol = 62 g mol -1.

18. Either

(a) A first-order reaction has a rate constant
1 × 15 ´ 10 -3 s -1. How long will 5 g of this reactant

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take to reduce to 3 g? 2

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c. o(b) Derive the integrated rate expression of a zero-order sem
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reaction.

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19. (a) Write the formula of the coordination compound
tetraamine aquachlorido cobalt (III) chloride. 1

(b) Give one example of coordination isomerism. 1

HS/XII/SC/Ch/26/70 [ P.T.O.

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( 8 )

20. (a) Arrange the following set of compounds in order of
increasing boiling points : 1
1-chloropropane, isopropyl chloride, 1-chlorobutane
(b) Write the products of the following reaction : 1
Alc. KOH
H 3C —CH2 —CH2 —CH —CH 3 ¾ ¾ ¾ ¾ ¾¾® A + B
|
Br

21. (a) Complete the following reaction : 1
NH2

+ Br2 (aq)

(b) Why is methanamine a stronger base than
ammonia? 1

SECTION—C
( Marks : 21 )
Question Nos. 22 to 28 are short answer-type questions
carrying 3 marks each.

22. Either
(a) What type of deviation from Raoult’s law is observed
by mixing chloroform and acetone? What causes
this deviation? 1+1=2
(b) What is the value of van’t Hoff factor, i, for
aqueous K 2SO4 solution, assuming that it
undergoes complete dissociation in solution? 1

HS/XII/SC/Ch/26/70 [ Contd.

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(c) What is m
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s e meant by elevation of boiling point? 1
l a
g a
l boiling point of benzene is 353·23 K. When ag
a g of a non-volatile solute was dissolved in 90 g
(d) The
1·80
of benzene, the boiling point is raised to 354·11 K.
Calculate the molar mass of the solute. [K b for
benzene is 2·53 K kg mol -1] 2

23. (a) The cell in which the following reaction occurs
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2 Fe 3 + (aq) + 2 I - (aq) ¾¾® 2 Fe 2 + (aq) + I2 (s)

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has E cell = 0 × 236 V at 298 K. Calculate the standard

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Gibbs energy and the equilibrium
cell reaction. [Given, 1 F = 96500 C]
constant of the
2

(b) What is the meaning of the negative sign in the
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expression E Zn 2+ = -0 × 76 V ?
/Zn 1

24. Either
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c. o(a) Give one point of difference between order and sem .co
e m molecularity of a reaction.
l a 1

las ag
ag (b) The decomposition of HI is expressed by the
equation 2 HI (g ) ® H2 (g ) + I2 (g ). If during a certain
time interval, the rate of disappearance of HI is
1 × 8 ´ 10 -3 mol L -1 s -1, then what will be the rate
of appearance of H2 during the same time interval? 2

HS/XII/SC/Ch/26/70 [ P.T.O.

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( 10 )

Or
(c) For the reaction, 2 NO (g ) + O2 (g ) ® 2 NO2 (g ), the rate
equation is given by, r = K [NO (g )]2[O2 (g )] . Calculate
the overall order of this reaction. Is this reaction
an elementary reaction? Justify your answer. 1+1=2
(d) What is the order of the reaction if its unit of rate
constant, k is (i) s -1 and (ii) mol L -1 s -1? 1

25. Either
(a) Write the mechanism of the following SN1 reaction : 2
aq. NaOH
(CH 3 )3 C —Br ¾ ¾ ¾ ¾ ¾¾® (CH 3 )3 C —OH + NaBr

(b) Why is t-butyl bromide more reactive towards SN1
reaction as compared to n-butyl bromide? 1

Or
(c) How would you carry out the following conversions?
1×3=3
(i) Aniline to chlorobenzene
(ii) Benzene to diphenyl
(iii) But-1-ene to but-2-ene

26. Either
(a) Write the chemical equation for the preparation of
ethoxybenzene by Williamson’s synthesis. 1
(b) How do you carry out the following conversions? 1+1=2
(i) Aniline to phenol
(ii) Formaldehyde to ethanol

HS/XII/SC/Ch/26/70 [ Contd.

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(c) Arrange the following alcohols in decreasing order of

s l a
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acid strength : 1

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a
2-methylpropan-2-ol, propanol, propan-2-ol
(d) Predict the product of the following reaction : 1
CH3
H3C—C—OH Cu
?
573 K
CH3

(e) Give the equations only for the conversion of benzene
to phenol. 1

o m
c
. order of their
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27. (a) Arrange the following in decreasing
e
basic strength :
as 1
C2H 5NH2 , (C2H 5 )2 NH,gl(C2H 5 )3 N, C 6H 5NH2
a
(b) Identify the products of the following : 1×2=2

KCN LiAlH4
(i) CH 3 —CH2 —Br ¾ ¾ ¾
¾® A ¾ ¾ ¾ ¾¾® B

(ii) C 6H 5NH2 + CHCl 3 + KOH (alc.) ¾¾® ?

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28. Either
s e
s em (a) Name four complimentary bases present in a DNAa
g l 1
l a molecule.
a
ag (b) Name the vitamin whose deficiency causes muscular
weakness. 1

(c) Write the structure of products formed when
D-glucose is treated with NH2OH. 1

HS/XII/SC/Ch/26/70 [ P.T.O.

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( 12 )

Or

(d) What do you mean by denaturation of proteins? 1

(e) What are essential and non-essential amino acids?
Give one example of each type. 2

SECTION—D
( Marks : 8 )
Question Nos. 29 and 30 carrying 4 marks each.

29. (a) What is the oxidation number of Fe in [Fe(CN)6 ]-4 ? 1

(b) Give one example of a complex having tetrahedral
geometry and paramagnetic in nature. 1

(c) Which one is an inner-orbital complex? 1
[Co(NH 3 )6 ] + 3 or [CoF6 ]3-

(d) According to VBT, which one has the highest
paramagnetic character? 1
[Cr(H2O)6 ] + 3 or [Fe(H2O)6 ] + 2

30. (a) What are reducing and non-reducing sugars? 1

(b) What are epimers? 1

(c) Name one optically active amino acid and one
optically inactive amino acid. 1

(d) Why are carbohydrates generally optically active? 1

HS/XII/SC/Ch/26/70 [ Contd.

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m
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c. o ( Marks : 15 ) m .co
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Question Nos. 31 to 33 are long answer-type questions
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carrying 5 marks each.

31. Either
(a) Write two functions of salt bridge. 1
(b) Calculate the EMF of the cell in which the following
reaction takes place : 2

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Ni (s) + 2 Ag + (0 × 002 M ) ¾¾® Ni2 + (0 × 160 M ) + 2Ag (s)

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(Given that E cell = 1 × 05 V)
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la of Faraday is required
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(c) How much electricity in terms
a Al2O 3?
to produce 40 g of Al from
(F = 96500 C, Atomic mass of Al = 27) 2

Or
(d) Why does conductivity of a solution decrease with
dilution? 1
(e) What is cathodic protection?
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1
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m 1 .c
co (ii) Given molar conductivities at infinite dilution : sem
(f) (i) State Kohlrausch’s law.
.
s em g l a
la a
a 2 -1
Ba (OH ) 457 6 Scm mol
g
L M 2 = ×
a a 2
L M (BaCl2 ) = 240 × 6 Scm mol -1

LaM (NH4 Cl) = 129 × 8 Scm2 mol -1

Calculate LaM for NH4 OH. 2

HS/XII/SC/Ch/26/70 [ P.T.O.

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( 14 )

32. Either

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

(b) Draw the structures of permanganate ion. 1

(c) Why Cr 3+ is reducing and Mn 3+ is oxidizing when
both have d 4 -configuration? 1

(d) Give the reaction of potassium dichromate with (i) KI
and (ii) H2S (in acidic medium). 2

Or

(e) Why do transition metals easily form alloys with
other transition metals? 1

(f) Why is silver (Atomic number = 47) considered to
be a transition element whereas zinc (Atomic
number = 30) is not? 1

(g) Write the balanced chemical equation for the
reaction of KMnO4 with oxalic acid in acidic
medium. 1

(h) Write all the reactions occurring during the
preparation of potassium permanganate from
pyrolusite ore. 2

33. Either

(a) Would you expect benzaldehyde to be more reactive
or less reactive in nucleophilic addition reactions
than propanal? Explain your answer. 2

HS/XII/SC/Ch/26/70 [ Contd.

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m
(b)
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Identify the products A, B, C and D from the following
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sequence of reactions :
m
2
s e m
s e Mg (i) CO2 dry ether
l a
a ag
CH3CH2Br A B

g l dry ether (ii) H3O+
a Br2/KOH
NH3 D

D C

(c) Predict the product of the following reaction : 1
O
C
CH3 H+
+ CH3CH2NH2 ?
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s e
la
(d) Write the structures of pentan-2-one and

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pentan-3-one and give a simple chemical test to
distinguish between them. 2

(e) Predict the structures of the products A, B, C and D
from the following reactions : 1×2=2
CO, HCl HNO3/H2SO4
(i) A B
anhy. AlCl3/CuCl

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(i) LiAlH4/ether anhy. CrO3
m (ii) CH3COOH C D

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+

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(ii) H3O

m (f) s e
s e g l a
la
The pK a values of 4-methoxybenzoic acid 4-nitro-

g a
benzoic acid and benzoic acid are 4·46, 3·41 and 4·19
a respectively. Which of these aromatic carboxylic
acids is the most acidic and why? 1

HHH

HS/XII/SC/Ch/26/70 26K—5860

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