Karnataka 2nd PUC Question Paper 2025 Answer Key Chemistry

Government of Karnataka
Karnataka Secondary Education Examination Board

Question Paper
ANSWER KEY

1
KARNATAKA SCHOOL EXAMINATION & ASSESSMENT BOARD
II PUC EXAMINATION–1; MARCH–2025
SUBJECT: 34-CHEMISTRY MODEL ANSWERS MAX.MARKS: 70
PART-A
I. Select the correct option from the given choices: 15 × 1=15
1) Incorrect statement regarding vitamins,
a) Excess vitamin intake is harmful
b) Most of the vitamins contain amino groups
c) Vitamins can be produced by plants
d) Vitamin deficiency causes diseases
Ans: b) Most of the vitamins contain amino groups (or)
1
Most of the vitamins contain amino groups (or) b)
2) Camphor in nitrogen gas, is an example of __________.
a) liquid Solutions b) solid Solutions
c) gaseous Solutions d) aqueous solution
Ans: c) gaseous Solutions (or) gaseous Solutions (or) c) 1
3) Which of the following is not a subdivision of structural isomerism?
a) Coordination isomerism b) Linkage isomerism
c) Ionisation isomerism d) Geometrical isomerism
Ans: d) Geometrical isomerism (or) Geometrical isomerism (or) d) 1
4) Cumene hydroperoxide on hydrolysis with dilute acid gives _________.
a) alcohol and phenol b) only phenol
c) phenol and acetone d) alcohol and acetone
Ans: c) phenol and acetone (or) phenol and acetone (or) c) 1
5) An example of a pseudo first-order reaction is,
a) The decomposition of gaseous ammonia on a hot platinum surface
b) Photochemical reaction between hydrogen and chlorine
c) Inversion of cane sugar
d) Hydrogenation of ethene
Ans: c) Inversion of cane sugar (or) Inversion of cane sugar (or) c) 1
6) The hybridisation of ‘N’ atom in trimethyl amine is,
a) sp3 b) sp2 c) sp d) dsp2
Ans: a) sp3 (or) sp3 (or) a) 1
7) The IUPAC name of

a) 3-bromobutyraldehyde b) 2-bromopropanaldehyde
c) 3-bromobutanal d) 2-bromobutanal
Ans: c) 3-bromobutanal (or) 3-bromobutanal (or) c) 1
8) Select non-semiconductor from the following,
a) silicon b) carbon-black
c) gallium arsenide d) doped silicon
Ans: b) carbon-black (or) carbon-black (or) b) 1
9) Statement I: Ammonolysis of alkyl halides has the disadvantage of yielding a mixture of
primary, secondary and tertiary amines and also a quaternary ammonium salt.
Statement II: Tertiary amine is obtained as a major product by taking large excess of ammonia
in ammonolysis of alkyl halides.
In the light of the above statements, choose the appropriate answer from the options given below:
a) Statement I is incorrect but Statement II is correct
b) Both Statement I and Statement II are correct
c) Both Statement I and Statement II are incorrect
d) Statement I is correct but Statement II is incorrect

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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Ans: d) Statement I is correct but Statement II is incorrect (or)
1
Statement I is correct but Statement II is incorrect (or) d)
10) The structure of pentacarbonyliron(0) is,
a) tetrahedral b) trigonal bipyramidal
c) octahedral d) square pyramidal
Ans: b) trigonal bipyramidal (or) trigonal bipyramidal (or) b) 1
11) Two compounds ‘A’ and ‘B’ were being tested for their boiling points. It was observed that ‘A’
started boiling after ‘B’, when both were subjected to same conditions. If the compound ‘B’ is
acetone, which of the following can be compound ‘A’?
a) Propanal b) Propan-1-ol
c) Methoxyethane d) n-Butane
Ans: b) Propan-1-ol (or) Propan-1-ol (or) b) 1
12) Select the correct order of melting points of isomeric dichlorobenzenes.
a) o-dichlorobenzene > m-dichlorobenzene > p-dichlorobenzene
b) p-dichlorobenzene > m-dichlorobenzene > o-dichlorobenzene
c) p-dichlorobenzene > o-dichlorobenzene > m-dichlorobenzene
d) m-dichlorobenzene > o-dichlorobenzene > p-dichlorobenzene
Ans: c) p-dichlorobenzene > o-dichlorobenzene > m-dichlorobenzene (or)
1
p-dichlorobenzene > o-dichlorobenzene > m-dichlorobenzene (or) c)
13) Match the following given in List I with List II:
List I List II
i) V2O5 A) Oxidation of ethyne to ethanal
ii) TiCl4 with Al(CH3)3 B) Polymerisation of alkynes
iii) PdCl2 C) Oxidation of SO2 in the manufacture of sulphuric acid
iv) Nickel complexes D) Manufacture polyethylene
Choose the correct option:
a) i-C, ii-D, iii-A, iv-B
b) i-A, ii-B, iii-C, iv-D
c) i-A, ii-C, iii-B, iv-D
d) i-C, ii-A, iii-D, iv-B
Ans: a) i-C, ii-D, iii-A, iv-B (or) i-C, ii-D, iii-A, iv-B (or) a) 1
14) Which of the following explains the increase in the reaction rate by a catalyst?
a) Catalyst decreases the rate of backward reaction so that rate of forward reaction increases
b) Catalyst provides extra energy to reacting molecules, so that they produce effective collisions
c) Catalyst provides an alternative pathway by reducing the activation energy between the
reactants and products
d) Catalyst increases the number of collisions between the reacting molecules
Ans: c) Catalyst provides an alternative pathway by reducing the activation energy
between the reactants and products (or)
Catalyst provides an alternative pathway by reducing the activation energy 1
between the reactants and products (or) c)
15) Sufficient amount of 2-methylpropan-2-ol heated with 20% phosphoric acid at 358 K gives main
product ‘X’ with the elimination of water and tert-butyl alcohol undergoes dehydration when it
is passed over heated copper at 573 K gives ‘Y’
Pick the correct statement regarding X and Y.
a) The boiling points of ‘X’ and ‘Y’ are equal
b) The boiling point of ‘X’ is greater than the boiling point of ‘Y’
c) The boiling point of ‘X’ is lesser than the boiling point of ‘Y’
d) At room temperature both ‘X’ and ‘Y’ exists as a solids
Ans: a) The boiling points of ‘X’ and ‘Y’ are equal
1
(or) The boiling points of ‘X’ and ‘Y’ are equal (or) a)
IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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II. Fill in the blanks by choosing the appropriate word from those given in the brackets: 5×1=5
[carbocation, pre-exponential, exponential, unpaired, carbohydrate, CCl 2F2]
16) Arrhenius factor is also called _________ factor.
Ans: pre-exponential 1
17) Paramagnetism arised from the presence of ________ electrons.
Ans: unpaired 1
18) _________ is one of the most common freon in industrial use.
Ans: CCl2F2 1
19) The electrophilic attack of H3O on alkene forms __________.
Ans: carbocation 1
20) The hormone glucorticoids control the __________ metabolism.
Ans: carbohydrate 1
PART - B
III. Answer any three of the following. Each question carries 2 marks. 3×2=6
21) Explain Wurtz reaction with suitable chemical equation.
Ans: Alkyl halides react with sodium in dry ether to give hydrocarbons. 1
2RX+2Na ⎯⎯ → RR + 2NaX 1
(or) (or)
2
(or)
(Any suitable chemical equation; statement 1 mark and equation 1 mark (or) self-explanatory
2
equation 2 mark)

22) Molarity (M), molality (m) and mole fraction (χ) are some methods for expressing
concentration of solutions.
Which of these are temperature dependent? Give reason.
Ans: Molarity (M) is temperature dependent. 1
Reason: Molarity is a function of temperature. This is because volume depends on
temperature. 1
(or)
Volume of thesolution varies with the change in temperature. (or)
1 1
Molarity  (or) Molarity 
Volume of the solution Temperature
23) What are non-essential amino acids? Name an optically inactive naturally occurring α-
amino acid.
Ans: The amino acids, which can be synthesised in the body, are known as non-essential 1
amino acids.
Optically inactive naturally occurring α-amino acid: Glycine (or) Gly 1
24) Write any two characteristic properties of interstitial compounds.
Ans: (i) They have high melting points, higher than those of pure metals.
(ii) They are very hard.
2
(iii) They retain metallic conductivity.
(iv) They are chemically inert. (Any Two; 1 mark for each)

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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25) While separating a mixture of ortho and para nitrophenols by steam distillation, name the
isomer which will be steam volatile. Give reason.
Ans: o-Nitrophenol 1
Reason: Due to the presence of intramolecular hydrogen bonding of o-Nitrophenol.
1
(or) Absence of intermolecular hydrogen bonding.
PART - C
IV. Answer any three of the following. Each question carries 3 marks. 3×3=9
26) State any three postulates of Werner's theory of coordination compounds
Ans: 1. In co-ordination compounds metals show two types of valences (linkages)
a) Primary valency b) Secondary valency
2. Primary valency ionisable, satisfied by negative ions.
3.Secondary valency non-ionisable, satisfied by negative ions or neutral molecules. 3
4. Secondary valency is equal to coordination number.
5. Secondary valency is directional in nature. (Any Three; 1 mark for each)
27) Write the balanced chemical equations involved in the manufacture of potassium
dichromate (K2Cr2O7) from chromite ore (FeCr2O4).
Ans: Step-1: 4 FeCr2O4 + 8 Na2CO3 + 7 O2 → 8 Na2CrO4 + 2 Fe2O3 + 8 CO2 1
Step-2: 2 Na2CrO4 + 2 H+ → Na2Cr2O7 + 2 Na+ + H2O 1
(or)
2 Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O 1
Step-3: Na2Cr2O7 + 2 KCl → K2Cr2O7 + 2 NaCl (1 mark for each step)
[Note: FeCr2O4 can also be written as FeO.Cr2O3]
28) [Co(NH3)5Br]SO4 is an octahedral coordination compound. Write its IUPAC name and
draw the diagram which indicates the splitting of d-orbitals in above complex with respect
to CFT (Crystal Field Theory).
Ans: IUPAC name: pentaamminebromidocobalt(III) sulphate. 1

Splitting of d-orbitals in above complex with respect to CFT (Crystal Field Theory):

2

29) What is lanthanoid contraction? Write one comparison and one difference between
lanthanoids and actinoids with respect to oxidation states shown by them.

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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Ans: The overall decrease in atomic and ionic radii from lanthanum to lutetium is called
lanthanoid contraction. 1

Comparison: Both exhibit common oxidation state of +3. 1
Difference:
Lanthanoids Actinoids
Lanthanoids not show greater range (variable Actinoids show greater range (variable
oxidation states) of oxidation states. oxidation states) of oxidation states. 1
Show maximum oxidation state is +4 Show maximum oxidation state +7
(Any one difference; for each 1 mark)
30) Write the facial (fac) and meridional (mer) isomeric structures of [Co(NH3)3(NO2)3].
Mention the coordination number of a metal ion in an above complex.
Ans:

2

(1 mark for each isomeric structure)
Coordination number: 6 (or) Six 1
V Answer any two of the folowing. Each question carries 3 marks: 2×3=6
31) Derive an integrated rate equation for the rate constant of zero-order reaction.
Ans: Consider a zero-order reaction, R → P
Let [R]0 be initial concentration of the reactant and
[R] be concentration of the reactant at any time “t”.
−d  R 
Rate = = k R 
0

dt 1
Where k is rate constant of a zero-order reaction
−d  R 
Rate = = k 1
dt
d[R] = − k dt

Integrating both sides: [R] = − kt + I ………….. (i) (I = Integration constant)
When t = 0, [R] = [R]0; Substituting in equation (i),
[R]0 = −k × 0 + I
[R]0 = I 1
Substituting value of ‘I’ in equation (i), [R] = −kt + [R]0

k=
R  − R 
0

t 1
(Any correct alternate derivations marks should be awarded)
IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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32) Write a neat labelled diagram, cell representation and half-cell reaction of Standard
Hydrogen Electrode (S.H.E.).
Ans:

1

(Any two labelling 1 mark)
1
Cell representation: Pt (s) |H2 (g) |H+ (aq)
Half-cell reaction:
1
At anode: H 2 (g) → H + (aq) + e −
2
(or)
+ − 1 1
At cathode: H (aq) + e → H 2 (g)
2
(or)

(Any one cell reaction; 1 mark)
33) Define azeotropes. What type of azeotropes are formed by solutions with negative
deviation from Raoult's law? Give an example for it.
Ans: It is defined as the “binary mixtures having the same composition in liquid and vapour 1
phase and boil at a constant temperature”.

Maximum boiling azeotropes 1

Example: 68% nitric acid and 32% water (or) 80% H2O and 20%HCl 1
(or) Chloroform and acetone (or) (Any suitable example)
34) Lead storage battery is commonly used as a secondary cell in automobiles. What is
secondary cell? Write down the reactions occurs at anode and cathode during discharging
of the lead storage battery.
Ans: Rechargeable cell is called secondary cell. 1

Anode: Pb(s) + SO42− (aq) ⎯⎯
→ PbSO4 (s) + 2e− 1

Cathode: PbO2 (s) + SO42− (aq) + 4H+ (aq) + 2e− ⎯⎯
→ PbSO4 (s) + 2H2O (l ) 1

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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PART - D
VI. Answer any four of the following. Each question carries 5 marks. 4 × 5 = 20
35) a) Write the SN2 mechanism for conversion of chloromethane to methanol. Mention its order.
b) What is racemic mixture? Represent the butan-2-ol in racemic mixture form.
Ans:
a)
2

(One mark for each step)
Order: 2 (or) Two 1
b) Equimolar mixture of d and l isomers is called racemic mixture.
(or) 1
Mixture of 50% d and 50% l isomers is called racemic mixture.
Represent the butan-2-ol in racemic mixture form:
dl-butan-2-ol (or) (±) butan-2-ol 1
36) a) Amylose and Amylopectin are two components starch. Write any two differences
between them.
b) List the any two nitrogenous bases commonly found in both RNA and DNA.
c) Name the enzyme that catalyses hydrolysis of maltose into glucose.
Ans: a) Amylase Amylopectin
It is water soluble component. It is water insoluble component.
It constitutes about 15-20% of starch. It constitutes about 80-85% of starch. 2
Amylose is unbranched chain polymer. Amylopectin is branched chain polymer.
α-D-glucose units held together by C1– α-D-glucose units held together by C1–
C4 glycosidic linkage. C4 and C1–C6 glycosidic linkage.
(Any other suitable answer, Any two; for each 1 mark)
b) Adenine (A), Guanine (G) and Cytosine (C) (Any two; for each 1 mark) 2
c) Maltase 1
37) a) Write the mechanism of addition of HCN to carbonyl group in presence of a base.
b) Explain Rosenmund reduction with chemical equation.
Ans: a)
1

2

(One mark for each step)

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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b) Hydrogenation of acyl chloride over palladium on barium sulphate gives aldehyde. This 1
reaction is called Rosenmund reduction.

1

(or)
(or)

2

(Statement 1 mark and equation 1 mark (or) self-explanatory equation 2 mark)
38) a) Describe carbylamine reaction with suitable chemical equation.
b) Explain the conversion of aniline to benzene diazonium chloride with chemical equation.
c) Among aryl amines and ammonia which is more basic?
Ans: a) Aliphatic and aromatic primary amines on heating with chloroform and ethanolic
potassium hydroxide form isocyanides or carbylamines. This reaction is known as 1
carbylamine reaction.

1
(or) (or)

2

(Any suitable chemical equation; statement 1 mark and equation 1 mark (or) self-
explanatory equation 2 mark)
b) Benzene diazonium chloride is prepared by the reaction of aniline with nitrous acid
1
(HNO2 (or) NaNO2+HCl) at 273-278K.

1
(or)
(or)
2

(Statement 1 mark and equation 1 mark (or) self-explanatory equation 2 mark)
c) Ammonia is more basic than aryl amines. 1

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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39 a) Lucas reagent is an important reagent which helps to distinguish between three classes of
alcohols.
Write the chemical composition of the Lucas reagent and explain how the above reagent
helps to distinguish 10 and 30-alcohols?
b) Illustrate preparation of ether by Williamson synthesis with a general chemical equation.
Ans: a) Chemical composition of the Lucas reagent:
Conc. HCl and Anhyd. ZnCl2 (or) Conc. HCl and ZnCl2 1
With Lucas reagent: Primary alcohols do not gives turbidity at room temperature. 1
Tertiary alcohols gives immediate turbidity.
1
b) Alkyl halide and sodium alkoxide reacts to gives ether. This reaction is called 1
Williamson’s ether synthesis.
1
(or) (or)
2

(Statement 1 mark and equation 1 mark (or) self-explanatory equation 2 mark)
40) An organic compound ‘A' on treatment with ethanoic acid in the presence of hydrochloric
acid gas as a catalyst produces an ester ‘B’. ‘A’ on oxidation with CrO3 in an anhydrous
medium gives ‘C’. ‘C’ is heated with concentrated KOH followed by acidification with
dilute HCl generates ‘A’ and ‘D’. Three moles of ‘D’ reacts with PCl3 gives three moles of
compound with molecular formula HCOCl and ‘E’. ‘D’ is reduced to ‘A’ by lithium
aluminium hydride followed by hydrolysis. Write the molecular formulas of the compound
‘A’, ‘B’, ‘C’, ‘D’ and ‘E’.
Ans: ‘A’ 1

‘B’ 1

‘C’ 1

‘D’ 1

‘E’ H3PO3 1
PART – E (PROBLEMS)
VII. Answer any three of the following. Each question carries 3 marks. 3×3=9
41) The initial concentration of N2O5 in the following first order reaction
1
N 2O 5 ( g ) ⎯⎯
→ 2NO 2 ( g ) + O 2 (g) was 1.24×10–2 mol L–1 at 318 K. The concentration of
2
N2O5 after 60 minutes was 0.20×10–2 mol L–1. Calculate the rate constant of the reaction at
318 K.

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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−2 −1
Ans: Given; [R]0 =1.24×10 mol L [R] = 0.20×10−2 mol L−1 k=?

2.303  R 0 1
k= log
t R 
2.303 1.24 10−2 1
k= log
60 0.20 10−2
2.303 2.303 2.303
k= log6.2 =  0.7924 (or) k=  0.7924
60 60 3600 1
−1 −4 −1
k = 0.0304 min−1 (or) k = 3.04 10−2 min −1 (or) k = 0.000506 s (or) k = 5.06 10 s

42) Calculate the osmotic pressure in pascals exerted by a solution prepared by dissolving 1.0
g of polymer of molar mass 185,000 in 450 mL of water at 37°C. [R = 8.314 ×103 Pa LK-
1
mol-1]
Ans: W2 = l g, M2 =185000 V = 450 mL = 0.45L

W2 RT nRT 1
π= (or) π=
M2V V

1 8.314 103  310 1
π=
185000  0.45

= 0.03096×103
1
= 30.96Pa
43) The standard electrode potential for Daniel cell is 1.1V. Calculate the standard Gibbs
energy for the reaction: Zn(s) + Cu 2+ (aq) ⎯⎯
→ Zn 2+ (aq) + Cu(s)
Ans: Δr Go = − nFEoCell 1

n =2, F = 96487 C mol–1 (or) F = 96500 C mol–1 and Eo Cell = 1.1V
1
Δr Go = − 2 × 96487 ×1.1 (or) Δr Go = − 2 × 96500 ×1.1
1
−1
Δr G = − 21227J mol (or) Δr G = − 212.27 kJ mol (or) Δr G = − 212.30 kJ mol
o −1 o −1 o

44) The vapour pressure of pure liquids A and B are 450 and 700 mm Hg respectively, at 350
K. Find out the composition of the liquid mixture if total vapour pressure is 600 mm Hg.
Ans: pAo =450 mm Hg and pBo =700 mm Hg

p total = p Bo + ( p A o − p Bo )  A 1
600= 700 + ( 450 − 700) A
100
A = = 0.40 1
250
B = 1 − 0.40 =0.60 1

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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45) The rate constant of a first order reaction increases from 2×10 –2 s–1 to 4×10–2 s–1 when the
temperature changes from 300 K to 310 K. Calculate the energy of activation (Ea).
[log 2 = 0.3010, log 2.5 = 0.3979, log 4 = 0.6020, R = 8.314 JK -1mol-1]
Ans:
k2 E a  T2 − T1 
log =  
k1 2.303R  T1T2  1

T1 = 300 K, T2 = 310 K, k1 = 2×10–2 and k2 = 4×10–2

4×10–2 Ea  310 − 300 
log =  
2×10–2 2.3038.314  300310  1

log 2 2.3038.314300 310
 Ea =
10

Ea = 53598.594Jmol–1 (or) Ea = 53.59 kJ mol–1 (or) Ea = 53.60 kJ mol–1 1

46) The conductivity of 0.001028 mol L–1 acetic acid is 4.95 × 10–5 S cm–1. Calculate its
dissociation constant if Λ o m for acetic acid is 390.5 S cm2 mol–1.
Ans: κ 1000 4.95×10−5 1000 1
Λm = = = 48.15 S cm 2 mol−1
c 0.001028
Λm 48.15 1
= = = 0.1233
Λmo 390.5

0.001028  ( 0.1233)
2
cα 2 1
k= = = 1.78 ×10−5 mol L−1
(1 −  ) (1 − 0.1233)
*******END*******

IIPUC EXAM-1, MARCH 2025 KSEAB 34-CHEMISTRY MODEL ANSWERS

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