CBSE Class 12 Chemistry 2026 question paper (56/3)

Maximum marks 70 · Time 3 hours · 3 sets

Try each question first, then open its model answer. Where the paper offers a choice, both questions are shown with OR between them.

Section A

1 mark each

Q.11 mark $Which of the following will be the least reactive towards nucleophilic substitution reaction ?$
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Q.21 mark $The intermediate formed during the slowest step involved in the dehydration of alcohol is :$
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Q.31 mark $\mathrm{[Co(en)_3]_2(SO_4)_3}$
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Q.41 mark $According to Werner’s theory, the primary valencies of the central metal atom :$
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Q.51 mark $\mathrm{(C_2H_5)_2NH}$
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Q.61 mark $Among the following, which is the strongest base ?$
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Q.71 mark $\mathrm{Cr_2O_7^{2-}}$
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Q.81 mark $The boiling point of an azeotropic mixture of water and ethanol is less than that of pure water and ethanol. The mixture shows :$
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Q.91 mark $2{\cdot}0$
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Q.101 mark $On electrolysis of very dilute aqueous solution of NaCl using platinum electrodes :$
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Q.111 mark $\mathrm{3A \rightarrow 2B}$
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Q.121 mark $On hydrolysis, which of the following carbohydrates gives only glucose ?$
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For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below :
Q.131 mark $Assertion (A) : Separation of Zr and Hf is difficult. Reason (R) : Because Zr and Hf lie in the same group of the periodic table.$
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Q.141 mark $Assertion (A) : Phenol is less acidic than 4-methylphenol. Reason (R) : The presence of an electron releasing group in phenol makes it less acidic.$
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Q.151 mark $Assertion (A) : Aromatic primary amines cannot be prepared by Gabriel phthalimide synthesis. Reason (R) : Gabriel phthalimide synthesis is used for the preparation of primary aliphatic amines.$
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Q.161 mark $Assertion (A) : Order of reaction is applicable to elementary as well as complex reactions. Reason (R) : Order of a reaction is an experimental quantity.$
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Section B

2 marks each

Q.172 marks $\mathrm{C_4H_9Br}$
Q.182 marks $\mathrm{A + B \rightarrow Products}$
Q.192 marks $Explain why, on addition of 1 mol of KCl to 1 litre of water, the boiling point of water increases, while the addition of 1 mol of methyl alcohol to 1 litre of water decreases the boiling point.$
Q.20 (a)2 marks $\mathrm{[PtCl_2(en)_2]SO_4}$
OR
Q.20 (b)2 marks $Define the following terms with a suitable example in each case : (i) Ambidentate ligand (ii) Double salt$
Q.212 marks $How do you explain the following ? (a) Presence of a straight chain in glucose (b) Presence of five - OH groups in glucose which are attached to different carbon atoms$

Section C

3 marks each

Q.223 marks $1{\cdot}5 \times 10^{10}$
Q.233 marks $\Lambda_m^{o}$
Q.243 marks $62\ \mathrm{g\ mol^{-1}}$
Q.25 (a)3 marks $\mathrm{[NiCl_4]^{2-}}$
OR
Q.25 (b)3 marks $(i) Name two coordination compounds which are important in biological systems. (ii) What is meant by chelate effect ? Give an example. (iii) Why are low spin tetrahedral complexes rarely formed ?$
Q.263 marks $Give reasons for the following : (a) Although chlorine is an electron-withdrawing group, yet it is ortho-, para-directing in electrophilic aromatic substitution reactions. (b) Aryl halides cannot be prepared by reacting phenol with concentrated halogen acids or phosphorus halides. (c) Chloroform is stored in closed dark coloured bottles.$
Q.273 marks $How will you obtain the following from benzenediazonium chloride ? Give chemical equations involved : (a) Chlorobenzene (b) Benzene (c) Benzonitrile$
Q.283 marks $\mathrm{C_3H_5N}$

Section D

Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Proteins and carbohydrates are essential constituents of our food. In addition, some simple molecules like vitamins and mineral salts also play an important role in the functions of organisms. All proteins are polymers of $\alpha$ -amino acids. Proteins can be classified into two types on the basis of their molecular shape — Fibrous and Globular proteins. Vitamins are accessory food factors required in the diet. They are classified as fat-soluble and water-soluble. Deficiency of vitamins leads to many diseases. Nucleic acids are the polymers of nucleotides which in turn consist of a base, a pentose sugar and phosphate moiety. There are two types of nucleic acids — DNA and RNA. Nucleic acids are responsible for the transfer of characters from parents to offsprings.
Q.29 (a)2 marks $Write the name of basic building units of proteins and nucleic acids. How can you differentiate between Fibrous and Globular proteins on the basis of their structures ?$
Q.29 (b) (i)1 mark $What products would be formed when a nucleotide from DNA containing thymine is hydrolyzed ?$
OR
Q.29 (b) (ii)1 mark $Write one structural difference between DNA and RNA.$
Q.29 (c)1 mark $Give one example each of a fat-soluble vitamin and a water-soluble vitamin.$
Alcohols have higher boiling points than other compounds, namely hydrocarbons, ethers and haloalkanes of comparable molecular masses. On oxidation, primary alcohols yield aldehydes with mild oxidizing agents and carboxylic acids with strong oxidizing agents. Secondary alcohols yield ketones on oxidation while tertiary alcohols are resistant to oxidation. Ethers may be prepared by dehydration of alcohols and Williamson synthesis. The C – O bond in ethers can be cleaved by hydrogen halides. The presence of – OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions due to resonance effect. In presence of NaOH, phenol generates phenoxide ion which is even more reactive than phenol. Thus, in alkaline medium, phenol undergoes Kolbe’s reaction.
Q.30 (a)2 marks $Name the reagents used in the following reactions : (i) Oxidation of a primary alcohol to aldehyde (ii) Oxidation of a primary alcohol to carboxylic acid$
Q.30 (b)1 mark $Write the reaction involved in Kolbe’s reaction.$
Q.30 (c) (i)1 mark $Why are tertiary alcohols resistant to oxidation ?$
OR
Q.30 (c) (ii)1 mark $\mathrm{(CH_3)_3C-O-C_2H_5} \xrightarrow{\mathrm{HI}}$

Section E

5 marks each

Q.31 (a)5 marks $\mathrm{Ti^{3+}}$
OR
Q.31 (b)5 marks $(i) A black-brown coloured solid (A) when fused with KOH in the presence of air, produces a dark green coloured compound (B) which on electrolytic oxidation in alkaline medium gives a dark purple coloured compound (C). Identify (A), (B) and (C). Write the reactions involved. (ii) What happens when an acidic solution of the green compound (B) is allowed to stand for some time ? Also write the equation involved. What is this type of reaction called ?$
Q.32 (a)5 marks $\mathrm{CH_3OH}$
OR
Q.32 (b)5 marks $\alpha$
Q.33 (a)5 marks $0{\cdot}01$
OR
Q.33 (b)5 marks $0{\cdot}001$

Section A

1 mark each

Q.11 mark $2{\cdot}0$
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Q.21 mark $On electrolysis of very dilute aqueous solution of NaCl using platinum electrodes :$
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Q.31 mark $Which of the following, compounds is most reactive towards nucleophilic substitution reaction with aqueous NaOH ?$
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Q.41 mark $The dehydration of 1°, 2° and 3° alcohols follows the order :$
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Q.51 mark $\mathrm{[Co(NH_3)_5\,(ONO)]\,SO_4}$
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Q.61 mark $According to Werner’s theory, the primary valencies of the central metal atom :$
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Q.71 mark $\mathrm{C_2H_5NH_2}$
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Q.81 mark $\mathrm{pK_b}$
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Q.91 mark $\mathrm{CrO_4^{2-}}$
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Q.101 mark $The boiling point of an azeotropic mixture of water and nitric acid is more than that of pure water and nitric acid. The mixture shows :$
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Q.111 mark $On hydrolysis, which of the following carbohydrates gives only glucose ?$
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Q.121 mark $\mathrm{2A \rightarrow 3B}$
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For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below :
Q.131 mark $Assertion (A) : Separation of Zr and Hf is difficult. Reason (R) : Zr and Hf have almost identical atomic and ionic radii due to lanthanoid contraction.$
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Q.141 mark $Assertion (A) : Phenol is more acidic than 4-methylphenol. Reason (R) : The presence of an electron releasing group in phenol makes it more acidic.$
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Q.151 mark $Assertion (A) : Aromatic primary amines can easily be prepared by Gabriel phthalimide synthesis. Reason (R) : Gabriel phthalimide synthesis is used to prepare only aliphatic primary amines.$
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Q.161 mark $Assertion (A) : Order of reaction is not applicable for elementary reaction but applicable for complex reaction. Reason (R) : Order of reaction is an experimental quantity.$
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Section B

2 marks each

Q.172 marks $Explain why, on addition of 1 mol of KCl to 1 litre of water, the boiling point of water increases, while the addition of 1 mol of methyl alcohol to 1 litre of water decreases the boiling point.$
Q.18 (a)2 marks $\mathrm{[PtCl_2(en)_2]SO_4}$
OR
Q.18 (b)2 marks $Define the following terms with a suitable example in each case : (i) Ambidentate ligand (ii) Double salt$
Q.192 marks $\mathrm{C_4H_9Br}$
Q.202 marks $\mathrm{A + B \rightarrow Products}$
Q.212 marks $How do you explain the following ? (a) Presence of a carbonyl group in glucose (b) Presence of five - OH groups in glucose$

Section C

3 marks each

Q.223 marks $\mathrm{CH_3}$
Q.233 marks $How will you obtain the following from benzene diazonium chloride ? Write chemical equations involved : (a) Phenol (b) Iodobenzene (c) p-Aminoazobenzene$
Q.243 marks $\mathrm{C_3H_5N}$
Q.253 marks $62\ \mathrm{g\ mol^{-1}}$
Q.26 (a)3 marks $\mathrm{[NiCl_4]^{2-}}$
OR
Q.26 (b)3 marks $(i) Name two coordination compounds which are important in biological systems. (ii) What is meant by chelate effect ? Give an example. (iii) Why are low spin tetrahedral complexes rarely formed ?$
Q.273 marks $\Lambda_m^{o}$
Q.283 marks $1{\cdot}5 \times 10^{10}$

Section D

Alcohols have higher boiling points than other compounds, namely hydrocarbons, ethers and haloalkanes of comparable molecular masses. On oxidation, primary alcohols yield aldehydes with mild oxidizing agents and carboxylic acids with strong oxidizing agents. Secondary alcohols yield ketones on oxidation while tertiary alcohols are resistant to oxidation. Ethers may be prepared by dehydration of alcohols and Williamson synthesis. The C – O bond in ethers can be cleaved by hydrogen halides. The presence of – OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions due to resonance effect. In presence of NaOH, phenol generates phenoxide ion which is even more reactive than phenol. Thus, in alkaline medium, phenol undergoes Kolbe’s reaction.
Q.29 (a)2 marks $Name the reagents used in the following reactions : (i) Oxidation of a primary alcohol to aldehyde (ii) Oxidation of a primary alcohol to carboxylic acid$
Q.29 (b)1 mark $Write the reaction involved in Kolbe’s reaction.$
Q.29 (c) (i)1 mark $Why are tertiary alcohols resistant to oxidation ?$
OR
Q.29 (c) (ii)1 mark $\mathrm{(CH_3)_3C-O-C_2H_5} \xrightarrow{\mathrm{HI}}$
Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Proteins and carbohydrates are essential constituents of our food. In addition, some simple molecules like vitamins and mineral salts also play an important role in the functions of organisms. All proteins are polymers of $\alpha$ -amino acids. Proteins can be classified into two types on the basis of their molecular shape — Fibrous and Globular proteins. Vitamins are accessory food factors required in the diet. They are classified as fat-soluble and water-soluble. Deficiency of vitamins leads to many diseases. Nucleic acids are the polymers of nucleotides which in turn consist of a base, a pentose sugar and phosphate moiety. There are two types of nucleic acids — DNA and RNA. Nucleic acids are responsible for the transfer of characters from parents to offsprings.
Q.30 (a)2 marks $Write the name of basic building units of proteins and nucleic acids. How can you differentiate between Fibrous and Globular proteins on the basis of their structures ?$
Q.30 (b) (i)1 mark $What products would be formed when a nucleotide from DNA containing thymine is hydrolyzed ?$
OR
Q.30 (b) (ii)1 mark $Write one structural difference between DNA and RNA.$
Q.30 (c)1 mark $Give one example each of a fat-soluble vitamin and a water-soluble vitamin.$

Section E

5 marks each

Q.31 (a)5 marks $0{\cdot}01$
OR
Q.31 (b)5 marks $0{\cdot}001$
Q.32 (a)5 marks $\mathrm{Ti^{3+}}$
OR
Q.32 (b)5 marks $(i) A black-brown coloured solid (A) when fused with KOH in the presence of air, produces a dark green coloured compound (B) which on electrolytic oxidation in alkaline medium gives a dark purple coloured compound (C). Identify (A), (B) and (C). Write the reactions involved. (ii) What happens when an acidic solution of the green compound (B) is allowed to stand for some time ? Also write the equation involved. What is this type of reaction called ?$
Q.33 (a)5 marks $\mathrm{CH_3OH}$
OR
Q.33 (b)5 marks $\alpha$

Section A

1 mark each

Q.11 mark $According to Werner’s theory, the primary valencies of the central metal atom :$
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Q.21 mark $\mathrm{[Pt(en)_2Cl_2]^{2+}}$
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Q.31 mark $\mathrm{(CH_3CO)_2O}$
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Q.41 mark $Which reagent is used to distinguish between primary, secondary and tertiary amines ?$
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Q.51 mark $On electrolysis of very dilute aqueous solution of NaCl using platinum electrodes :$
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Q.61 mark $The correct order of decreasing basic strength in aqueous solution of the following is :$
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Q.71 mark $2{\cdot}0$
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Q.81 mark $+1$
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Q.91 mark $\beta$
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Q.101 mark $Consider the following compounds : Chlorobenzene (I), 2,4,6-trinitrochlorobenzene (II), 2,4-dinitrochlorobenzene (III), 4-nitrochlorobenzene (IV) The correct order of increasing ease of nucleophilic substitution reactions of these compounds is :$
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Q.111 mark $\mathrm{NH_3}$
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Q.121 mark $1 mole of liquid A and 2 moles of liquid B make a solution having a total vapour pressure 40 torr. The vapour pressure of pure A and pure B are 30 torr and 45 torr respectively. The above solution :$
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For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below :
Q.131 mark $Assertion (A) : Ethers have lower boiling points than the boiling points of alcohols. Reason (R) : This is due to the presence of hydrogen bonding in alcohols.$
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Q.141 mark $Assertion (A) : Transition metals show their highest oxidation state with oxygen. Reason (R) : The ability of oxygen to form multiple bonds to metals.$
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Q.151 mark $Assertion (A) : Monobromination of aniline can be conveniently done by protecting the amino group by acetylation. Reason (R) : Acetylation increases the activation effect of the amino group.$
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Q.161 mark $Assertion (A) : Order of reaction is applicable to elementary as well as complex reactions. Reason (R) : For a complex reaction, molecularity has no meaning.$
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p (torr)	704	75	$34{\cdot}5$
$\mathrm{t_{1/2}}$ (min)	80	80	80

Section B

2 marks each

Q.172 marks $\mathrm{A + B \rightarrow Products}$
Q.182 marks $\mathrm{C_4H_9Br}$
Q.19 (a)2 marks $\mathrm{[PtCl_2(en)_2]SO_4}$
OR
Q.19 (b)2 marks $Define the following terms with a suitable example in each case : (i) Ambidentate ligand (ii) Double salt$
Q.202 marks $How do you explain the following ? (a) Presence of an aldehyde group in glucose (b) Presence of a primary alcoholic group in glucose$
Q.212 marks $Explain why, on addition of 1 mol of KCl to 1 litre of water, the boiling point of water increases, while the addition of 1 mol of methyl alcohol to 1 litre of water decreases the boiling point.$

Section C

3 marks each

Q.223 marks $\Lambda_m^{o}$
Q.233 marks $62\ \mathrm{g\ mol^{-1}}$
Q.24 (a)3 marks $\mathrm{[NiCl_4]^{2-}}$
OR
Q.24 (b)3 marks $(i) Name two coordination compounds which are important in biological systems. (ii) What is meant by chelate effect ? Give an example. (iii) Why are low spin tetrahedral complexes rarely formed ?$
Q.253 marks $How will you obtain the following from aniline ? Write the chemical equations involved : (a) Sulphanilic acid (b) 2,4,6-Tribromoaniline (c) Acetanilide$
Q.263 marks $\mathrm{C_3H_5N}$
Q.273 marks $1{\cdot}5 \times 10^{10}$
Q.283 marks $\mathrm{C_6H_{11}-CH_2-Cl}$

Section D

Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Proteins and carbohydrates are essential constituents of our food. In addition, some simple molecules like vitamins and mineral salts also play an important role in the functions of organisms. All proteins are polymers of $\alpha$ -amino acids. Proteins can be classified into two types on the basis of their molecular shape — Fibrous and Globular proteins. Vitamins are accessory food factors required in the diet. They are classified as fat-soluble and water-soluble. Deficiency of vitamins leads to many diseases. Nucleic acids are the polymers of nucleotides which in turn consist of a base, a pentose sugar and phosphate moiety. There are two types of nucleic acids — DNA and RNA. Nucleic acids are responsible for the transfer of characters from parents to offsprings.
Q.29 (a)2 marks $Write the name of basic building units of proteins and nucleic acids. How can you differentiate between Fibrous and Globular proteins on the basis of their structures ?$
Q.29 (b) (i)1 mark $What products would be formed when a nucleotide from DNA containing thymine is hydrolyzed ?$
OR
Q.29 (b) (ii)1 mark $Write one structural difference between DNA and RNA.$
Q.29 (c)1 mark $Give one example each of a fat-soluble vitamin and a water-soluble vitamin.$
Alcohols have higher boiling points than other compounds, namely hydrocarbons, ethers and haloalkanes of comparable molecular masses. On oxidation, primary alcohols yield aldehydes with mild oxidizing agents and carboxylic acids with strong oxidizing agents. Secondary alcohols yield ketones on oxidation while tertiary alcohols are resistant to oxidation. Ethers may be prepared by dehydration of alcohols and Williamson synthesis. The C – O bond in ethers can be cleaved by hydrogen halides. The presence of – OH group in phenols activates the aromatic ring towards electrophilic substitution and directs the incoming group to ortho and para positions due to resonance effect. In presence of NaOH, phenol generates phenoxide ion which is even more reactive than phenol. Thus, in alkaline medium, phenol undergoes Kolbe’s reaction.
Q.30 (a)2 marks $Name the reagents used in the following reactions : (i) Oxidation of a primary alcohol to aldehyde (ii) Oxidation of a primary alcohol to carboxylic acid$
Q.30 (b)1 mark $Write the reaction involved in Kolbe’s reaction.$
Q.30 (c) (i)1 mark $Why are tertiary alcohols resistant to oxidation ?$
OR
Q.30 (c) (ii)1 mark $\mathrm{(CH_3)_3C-O-C_2H_5} \xrightarrow{\mathrm{HI}}$

Section E

5 marks each

Q.31 (a)5 marks $\mathrm{CH_3OH}$
OR
Q.31 (b)5 marks $\alpha$
Q.32 (a)5 marks $0{\cdot}01$
OR
Q.32 (b)5 marks $0{\cdot}001$
Q.33 (a)5 marks $\mathrm{Ti^{3+}}$
OR
Q.33 (b)5 marks $(i) A black-brown coloured solid (A) when fused with KOH in the presence of air, produces a dark green coloured compound (B) which on electrolytic oxidation in alkaline medium gives a dark purple coloured compound (C). Identify (A), (B) and (C). Write the reactions involved. (ii) What happens when an acidic solution of the green compound (B) is allowed to stand for some time ? Also write the equation involved. What is this type of reaction called ?$