Class 12 Question Paper 2024-25 Chemistry (Half Yearly)

HALF YEARLY EXAM

QUESTION
PAPER
ORIGINAL EXAM PAPERS

HALF YEARLY EXAMINATION, 2024-25
CHEMISTRY
Time – 3:00 Hrs. Class – XII M.M. : 80
Date – 18.09.2024 (Wednesday)
Name of the student _______________________________________________Section _____
GENERAL INSTRUCTIONS:
1. There are 33 questions in this question paper with internal choice.
2. SECTION A consists of 16 multiple-choice questions carrying 1 mark each.
3. SECTION B consists of 5 short answer questions carrying 2 marks each.
4. SECTION C consists of 7 short answer questions carrying 3 marks each.
5. SECTION D consists of 2 case-based questions carrying 4 marks each.
6. SECTION E consists of 3 long answer questions carrying 5 marks each.
7. All questions are compulsory.
8. 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.
Q.1 What would be the major product formed when (CH3)3C–OH is heated at 358 K in the
presence of H3PO4:
a) (CH3)3COOH b) (CH3)3CHO c) (CH3)2C=CH2 d) (CH3)3C-O-C-(CH3)3
Q.2 Which among the following compound will exhibit optical isomerism
a) Tert-butylamine b) Sec-butylamine c) Isobutylamine d) n-butylamine
Q.3 Which of the following purines (nitrogenous bases with two-ring structure) are common to
RNA and DNA?
a) Adenine, Thymine b) Guanine, Thymine c) Thymine, Cytosine d) Adenine, Guanine
Q.4 Alkenes decolourise bromine water in presence of CCl4 due to formation of:
a) allyl bromide b) vinyl bromide c) bromoform d) vicinal dibromide
Q.5 Phenol and benzoic acid may be distinguished by their reaction with:
a) Aqueous NaOH b) Aqueous NaHCO3 c) Tollen’s reagent d) Fehling solution
Q.6 Which of the following alkyl iodide cannot be produced by the reaction of HI with an
appropriate ether:
(a) (CH3)3C–CH2–I (b) (CH3)2CH–I (c) C6H5CH2–I (d) C6H5–I
Q.7 Ankit has been given four organic compounds: a primary amine, a secondary amine, a
secondary alcohol and a tertiary alcohol. Which of the following can Ankit use to identify all
the compounds?
a) Tollen’s reagent and bromine water b) 2,4 DNP and Lucas reagent
c) Hinsberg's reagent and Lucas’s reagent d) Sodium metal and Hinsberg’s reagent
Q.8 Which of the following is not true about enzymes?
a) All enzymes are fibrous proteins
b) Enzymes are needed in small quantities

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c) Enzymes reduce the magnitude of activation energy.
d) They are specific for a reaction and the substrate.
Q.9 Identify the products (1) and (2) in the following reactions:
C2H5Cl + KCN ⎯⎯→ (1) and C2H5Cl + KNO2 ⎯⎯→ (2)
a) (1) C2H5CN (2) C2H5NO2 b) (1) C2H5NC (2) C2H5NO2
c) (1) C2H5CN (2) C2H5ONO d) (1) C2H5NC (2) C2H5ONO
Q.10 “Williamson synthesis of ether is an example of:
a) electrophilic substitution b) nucleophilic substitution
c) nucleophilic addition d) electrophilic addition
Q.11 Which of the following reactions can be used to obtain benzaldehyde from benzene?
a) Rosenmund’s Reduction b) Stephen’s Reaction
c) Etard’s Reaction d) Gatterman-Koch Reaction
Q.12 Which of the following is the correct order of the solubility in water?
a) propane < ethylamine < ethyl alcohol b) propane < ethyl alcohol < ethylamine
c) ethyl alcohol < propane < ethylamine d) ethyl alcohol < ethylamine < propane
Q.13 Given below are two statements labelled as Assertion (A) and Reason (R)
Assertion (A): Phenol on treatment with Br2 in CS2 gives ortho and para bromophenol.
Reason (R): Carbon disulphide is a solvent of low polarity, hence leads to monobromination of
phenols
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.
b) A is true but R is false.
c) A is false but R is true.
Q.14 Given below are two statements.
Statement 1: Benzaldehyde is more reactive than ethanal towards nucleophilic attack.
Statement 2: The overall effect of – I and +R effect of phenyl group decreases the electron
density on the carbon atom of >C =O group in benzaldehyde.
Select the most appropriate answer from the options given below:
a) Statement 1 is correct and statement 2 is incorrect.
b) Statement 1 is incorrect and statement 2 is correct.
c) Statement 1 and 2 both are correct.
d) Statement 1 and 2 both are incorrect.
Q.15 Given below are two statements labeled as Assertion (A) and Reason (R).
Assertion: Glucose reacts with hydroxylamine to form an oxime and alsoadds a molecule of
hydrogen cyanide to give cyanohydrin.
Reason: The carbonyl group is present in the open chain structure of glucose.
Select the most appropriate answer from the options given below:
a) Both assertion and reason are correct statements, and reason is the correct explanation of
the assertion.

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b) Both assertion and reason are correct statements, but reason is not the correct explanation
of the assertion.
c) Assertion is correct, but reason is wrong statement.
d) Assertion is wrong, but reason is correct statement
Q.16 Given below are two statements labeled as Assertion (A) and Reason (R)
Assertion (A): Halogens are ortho and para-directing groups
Reason (R): Halogens are electron-withdrawing groups
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.
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.
Answer the following questions.
Q.17 Explain why the dipole moment of chlorobenzene is lower than that of cyclohexyl chloride
Q.18 Give an example of:
a) an amine each with basic strength greater than and less than N-Methylmethanamine in
gaseous state
b) an isomeric amine each with boiling point less than and more than N-Ethyl ethanamine.
Q.19 What is the difference between essential and non-essential amino acids?
Q.20 Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of
the corresponding phenoxide lons.
OR
Grignard reagent should be prepared under anhydrous conditions. Explain.
Q.21 Arrange the following as indicated
a) n-Butane, Propan-1-ol, Propanal, Acetone, Methoxymethane (increasing order of boiling
point)
b) Acetaldehyde, Acetone, Acetophenone, (increasing order of reactivity towards nucleophilic
addition)
SECTION - C
This section contains 7 questions with internal choice in one following questions are short answer
type and carry 3 marks each.
Q.22 Write short notes on the following:
1. Carbylamine reaction 2. Diazotisation 3. Hoffmann’s bromamide reaction
Q.23 An organic compound ‘A’ is having a molecular formula C7H8O. On oxidation with acidified
KMnO4 it forms compound ‘B’. Compound ‘B’ can also be obtained from compound C, on its
reaction with NaOH and then with CO2 followed by hydrolysis. Compound C can be easily
formed when butylphenylether is made to react with HI.

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Identify the compound A, B and C. Write the chemical reactions involved.
Q.24 Give equations of the following reactions:
a) Oxidation of propan-1-ol with alkaline KMnO4 solution.
b) Br2 / water in phenol.
c) Dilute HNO3 with phenol.
OR
How are the following conversions carried out?
a) Propene → Propan-2-ol
b) Benzyl chloride → Benzyl alcohol
c) Ethyl magnesium chloride → Propan-1-ol.
Q.25 Same alkyl halides undergo substitution whereas some undergo elimination reaction on
treatment with bases, in different medium. Discuss the role of medium with the help of
example which are responsible for this difference.
OR
Write the structures of the following compounds.
a) α-Methoxy propionaldehyde
b) 3-Hydroxybutanal
c) 2-Hydroxycyclopentane carbaldehyde
Q.26 What is meant by the following terms? Give an example of the reaction in each case.
a) Cyanohydrin b) Acetal c) Semicarbazone
Q.27 Convert Propanamide to the following compounds in not more than two steps:
a) N- Ethylpropanamine b) Ethanol c) Propanoic acid
Q.28 What happens when D- glucose is treated with following reagents
(a) Bromine water (b) HI (c) HNO3
SECTION - D
Read the passage given below and answer the following questions: (1+1+2)
Q.29 Both alcohols and phenols are acidic in nature, but phenols are more acidic than alcohols.
Acidic strength of alcohols mainly depends upon the inductive effect. Acidic strength of
phenols depends upon a combination of both inductive effect and resonance effects of the
substituent and its position on the benzene ring. Electron withdrawing groups increases the
acidic strength of phenols whereas electron donating groups decreases the acidic strength of
phenols. Phenol’s a weaker acid than carboxylic acid.
a) Why Phenols are more acidic as compared to alcohols?
b) The correct decreasing order of pKa value is

c)
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c) Phenol when treated with the sodium metal and CH3 MgBr separately liberates A(g) and
B(g). Identify both liberated gases.
OR
c) Discuss the mechanism of esterification reaction.
Read the passage given below and answer the following questions: (1+1+2)
Q.30 The amines are basic in nature due to the presence of a lone pair of electrons on N-atom of the
-NH2 group, which it can donate to electron deficient compounds. Aliphatic amines are
stronger bases than NH3 because of the +1 effect of the alkyl groups. Greater the number of
alkyl groups attached to N-atom, higher is the electron density on it and more will be the
basicity. Thus, the order of basic nature of amines is expected to be 3° > 2° > 1°, however the
observed order is 2° > 1° > 3°. This is explained on the basis of crowding on N-atom of the
amine by alkyl groups which hinders the approach and bonding by a proton, consequently, the
electron pair which is present on N is unavailable for donation and hence 3° amines are the
weakest bases. Aromatic amines are weaker bases than ammonia and aliphatic amines.
Electron -donating groups such as -CH3-OCH3, etc. increase the basicity while electron-
withdrawing substitutes such as -NO2, -CN, halogens, etc. decrease the basicity of amines. The
effect of these substituents is more at para than at meta-positions.
(a) Why do -NH2 group facilitates Electrophilic attack in aniline?
(b) Arrange the following in increasing order of basicity in aqueous medium.
C2H5)2NH, (C2H5)3N, C2H5NH2, NH3
(c) Electrophilic substitution is more readily carries out in aromatic amines than in benzene. Why?
OR
(c) Aniline does not undergoes friedel craft reaction. Explain.
SECTION - E
The following questions are long answer type and carry 5 marks each. All questions have an internal
choice.
Q.31 Answer the following questions:
a) Draw the structure of the ethylene ketal of hexan-3-one.
b) Between Benzoic acid and acetic acid which is more acidic and why?
c) An optically active organic compound ‘A’, with molecular formula, C5H10O2 when treated
with Chlorine in the presence of Red Phosphorous forms compound ‘B’, C5H9O2Cl, whereas
when it is treated with thionyl chloride forms compound ‘C’, C5H9OCl. Compound C, on further
hydrogenation with palladium on BaSO4 in the presence of S, forms compound D, C5H10O.
Compound D gives positive Tollen’s test and regenerates A. A can also be obtained by base
hydrolysis and further acidification of C. Write the reaction for the formation of ‘A’ from ‘C’
and Identify A, B, C, D.
OR
a) Bring about the following conversions:
i) Propanal to 2-methyl pentanol
ii) Iodobenzene to benzoic acid
b) Though Carboxylic acids have >C=O group in their structure, but they are not prone to
nucleophilic addition reactions. Why?

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c) An organic compound A, with molecular formulae C9H12 is oxidized to monocarboxylic acid
B, C7H6O2 on vigorous oxidation with Potassium permanganate, whereas when oxidized in
presence of air and further treated with dilute acid forms phenol. Sodium salt of B finds
use as a food preservative and esters of B are used in perfumery. Identify A and B and
write the equation.
Q.32 What happens when:
a) n-butyl chloride is treated with alcoholic KOH.
b) bromobenzene is treated with Mg in the presence of dry ether.
c) chlorobenzene is subjected to hydrolysis.
d) ethyl chloride is treated with aqueous KOH
e) methyl bromide is treated with sodium in the presence of dry ether.
OR
Among all the isomers of molecular formula C4H9Br identify
a) (i) the one isomer which is optically active.
(ii) the one isomer which is highly reactive towards SN2 reaction.
(iii) the two isomers which give same product on dehydrohalogenation with alcoholic KOH.
b) Haloarenes are less reactive than haloakanes towards nucleophilic substitution reaction.
Explain:
Q.33 Answer the following questions:
i) a) Name an important carbohydrate which makes the cell wall of bacteria and plants. What is
the basic unit of this carbohydrate?
b) How are these basic units linked to each other, name the linkage.
c) Draw the Haworth structure of the basic unit.
ii) Identify the disaccharide with molecular formulae, C12H22O11, which produces 2 moles of α-D
(+) Glucose on hydrolysis. What will be the observation when Tollen’s reagent is added to such
a disaccharide.
iii) Change in optical rotation is observed when sucrose is hydrolysed. What is the reason for the
inversion of configuration observed?
OR
Answer the following questions:
(i) a) A polynucleotide chain is seen to produce pentose sugar, phosphoric acid, Adenine,
Guanine, Cytosine and Thymine on complete hydrolysis. Name the nucleic acid having such a
polynucleotide chain. How are the bases paired in this polynucleotide?
b) What links these nucleotides together in a polynucleotide?
c) Give one important function and one application of the above nucleic acid.
ii) Keratin is a hair protein. What kind of tertiary protein is this? Describe the structure and
links present in this protein. Comment on its solubility in water?

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Study Materials
Notes

Model Papers Class 6 Notes

Sample Papers Class 7 Notes
Half Yearly Sample Papers Class 8 Notes

Class 9 Notes
Important Resources
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Periodic Table
Class 11 Notes
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Maps of India / World Class 12 Notes

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