CBSE Class 12 Chemistry Question Paper 2026 with Solutions (Set 3 - 56/1/3)

In the ring structure of fructose, the anomeric carbon is

• (A) C - 1
• (B) C - 2
• (C) C - 3
• (D) C - 5

Which of the following is the correct expression of \( K_f \) which depends upon the nature of solvent ?

• (A) \( K_f = \dfrac{M_1 \times T_f^{2}}{R \times 1000 \times \Delta_{fus}H} \)
• (B) \( K_f = \dfrac{R \times M_1 \times \Delta_{fus}H}{1000 \times T_f^{2}} \)
• (C) \( K_f = \dfrac{R \times T_f^{2} \times \Delta_{fus}H}{1000 \times M_1} \)
• (D) \( K_f = \dfrac{R \times M_1 \times T_f^{2}}{1000 \times \Delta_{fus}H} \)

Which of the following transition metals has lowest enthalpy of atomisation ?

• (A) Cr
• (B) V
• (C) Mn
• (D) Fe

Which of the following curve represents the first order reaction?

• (A) A
• (B) B
• (C) C
• (D) D

Aniline on direct nitration yields

• (A) 51%-ortho, 47%-para, 2%-meta derivatives
• (B) 51%-meta, 47%-ortho, 2%-para derivatives
• (C) 51%-para, 47%-meta, 2%-ortho derivatives
• (D) 51%-ortho, 47%-meta, 2%-para derivatives

Which of the following is 'not' true about enantiomers?

• (A) They have the same chemical reactivity.
• (B) They have the same specific rotation.
• (C) They have the same melting or boiling point.
• (D) They have the same refractive index.

The secondary valency of Co in \( \mathrm{[Co(en)_3]^{3+}} \) is

• (A) 4
• (B) 3
• (C) 5
• (D) 6

At low temperature, phenol on reaction with \( \mathrm{Br_2} \) in \( \mathrm{CS_2} \) gives

• (A) 2, 4, 6-Tribromophenol
• (B) a mixture of ortho-and para-bromophenol
• (C) ortho-bromophenol only
• (D) para-bromophenol only

How the conductivity varies on decreasing concentration for both weak and strong electrolytes ?

• (A) It increases for weak electrolyte and decreases for strong electrolyte.
• (B) It decreases for weak electrolyte and increases for strong electrolyte.
• (C) It increases for both weak and strong electrolytes.
• (D) It decreases for both weak and strong electrolytes.

\( \mathrm{CH_3-NH_2} \) on reaction with \( \mathrm{(CH_3CO)_2O} \) gives

• (A) \( \mathrm{CH_3CONH_2} \)
• (B) \( \mathrm{CH_3COONHCH_3} \)
• (C) \( \mathrm{CH_3-NH-C(=O)-CH_3} \)
• (D) \( \mathrm{CH_3-C(=O)-CH_2-NH_2} \)

The activation energy of a reaction can be determined from the slope of which of the following curves ?

• (A) \( \ln k \) vs. \( T \)
• (B) \( \ln k \) vs. \( \dfrac{1}{T} \)
• (C) \( \ln \dfrac{k}{T} \) vs. \( T \)
• (D) \( \dfrac{T}{\ln k} \) vs. \( \dfrac{1}{T} \)

Identify "X" in the following reaction :

\( \mathrm{CH_3-CO-CH_2-CO-O-CH_3} \xrightarrow{\mathrm{NaBH_4}} \text{X} \)

"X" is

• (A) \( \mathrm{CH_3-CH(OH)-CH_2-CO-O-CH_3} \)
• (B) \( \mathrm{CH_3-CO-CH_2-CH_2-OH} \)
• (C) \( \mathrm{CH_3-CH(OH)-CH_2-CH_2-OH} \)
• (D) \( \mathrm{CH_3-CH(OH)-CH_2-COOH} \)

Assertion (A) : The presence of -OH group in phenols directs the incoming group at ortho- and para- positions.

Reason (R) : -OH group in phenols deactivates the aromatic ring.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false.
• (D) Assertion (A) is false, but Reason (R) is true.

Assertion (A) : Actinoids show irregularities in their electronic configurations.

Reason (R) : Due to varying stabilities of \( f^0 \), \( f^7 \) and \( f^{14} \) occupancies of the 5f orbitals.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false.
• (D) Assertion (A) is false, but Reason (R) is true.

Assertion (A) : The pentaacetate of glucose does not react with \( \mathrm{H_2N-OH} \).

Reason (R) : It indicates the absence of free -CHO group in glucose.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false.
• (D) Assertion (A) is false, but Reason (R) is true.

Assertion (A) : It is not possible to separate the components of an azeotrope by fractional distillation.

Reason (R) : Minimum boiling azeotrope is formed by the solutions showing large positive deviation from Raoult's law.

• (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• (C) Assertion (A) is true, but Reason (R) is false.
• (D) Assertion (A) is false, but Reason (R) is true.

What type of deviation is shown by a mixture of chloroform and acetone from Raoult's law ? Give reason. What will happen to the boiling point of the solution on mixing chloroform and acetone ?

Following reaction takes place in one step:

\(2A + B \rightarrow 2C\)

How will the rate of above reaction change if the volume of the reaction vessel is decreased to one third of its original volume? Will there be any change in the order of reaction with the reduced volume?

Write IUPAC names of the following coordination compounds:

(i) \([Ag(NH_3)_2][Ag(CN)_2]\)

(ii) \(K_3[Fe(C_2O_4)_3]\)

(i) Give a chemical test to show that \([Co(NH_3)_5SO_4]Cl\) and \([Co(NH_3)_5Cl]SO_4\) are ionisation isomers.

(ii) What is meant by the 'Chelate effect'? Give an example.

Differentiate between the following :

(i) Fibrous protein and Globular protein

(ii) Peptide linkage and Phosphodiester linkage

Why are haloarenes less reactive towards nucleophilic substitution reaction? Give two reasons.

Calculate the boiling point of a solution containing 0.61 g of benzoic acid (Molar mass = 122 g mol\(^{-1}\)) in 5 g of \(CS_2\) in which it dimerises to the extent of 88%. The boiling point and \(K_b\) of \(CS_2\) are 46.2 \(^\circ C\) and 2.3 K kg mol\(^{-1}\) respectively.

Write the reaction involved in the following:

Reimer-Tiemann reaction

Write the reaction involved in the following:

Kolbe's reaction

Write the reaction involved in the following:

Friedel-Crafts acylation of anisole

Give reason for the following:

Nucleophilic addition of ammonia and its derivatives does not occur with carbonyl group in strongly acidic medium.

Nucleophilic addition of ammonia and its derivatives does not occur with carbonyl group in strongly acidic medium.

Give reason for the following:

Carboxylic acids have higher boiling point than alcohols of comparable molecular masses.

Give reason for the following:

Alpha (\(\alpha\)) hydrogens of aldehydes and ketones are acidic in nature.

For the first order thermal decomposition reaction, following data was obtained :

\(C_2H_5Cl(g) \rightarrow C_2H_4(g) + HCl(g)\)

Calculate rate constant.
[Given : log 3 = 0.48]

How do you explain the presence of following in open structure of glucose ?

(a) all the six carbon atoms are in a straight chain.
(b) five \(-OH\) groups which are attached to different carbon atoms.
(c) an aldehyde group.

How do you explain the presence of following in open structure of glucose ?

(a) all the six carbon atoms are in a straight chain.

(b) five \( \mathrm{-OH} \) groups which are attached to different carbon atoms.

(c) an aldehyde group.

Compound 'X' with molecular formula \(C_4H_9Br\) reacts with aqueous KOH to give an alcohol. The rate of this reaction depends only on the concentration of the compound 'X'. When an optically active isomer 'Y' of the compound 'X' was treated with aqueous KOH solution, the rate of reaction was found to be dependent on concentration of compound 'Y' and aqueous KOH both.

(a) Write down the structural formula of both 'X' and 'Y'.

(b) Out of 'X' and 'Y', which one will undergo racemisation and why?

(c) Out of 'X' and 'Y', which one will form product with inversion of configuration and why?

Answer the following:

(i) Why is the Equilibrium Constant \(K_c\) related to \(E^\circ_{cell}\) and not to \(E_{cell}\)?

(ii) Two metals 'A' and 'B' have standard electrode potential values of \(-0.24\) V and \(+0.80\) V respectively. Which of these will liberate hydrogen gas from dil. \(H_2SO_4\)?

(iii) Write the cell reaction which occurs in lead storage battery when it is in charging.

What type of battery is Mercury cell? Why it is more advantageous than dry cell? Write overall reaction taking place in Mercury cell.

The reaction of amines with mineral acids to form ammonium salts shows that these are basic in nature. Aliphatic amines are stronger bases than ammonia whereas aromatic amines are weaker bases than ammonia. Aliphatic and aromatic primary and secondary amines react with acid chlorides, anhydrides and esters by nucleophilic substitution reaction. The main problem encountered during electrophilic substitution reactions of aromatic amines is that of their high reactivity. Substitution tends to occur at ortho-and para-positions. Hinsberg reagent is used for the identification and distinction between primary, secondary and tertiary amines. Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes.

30(a)(i). Why \(CH_3 - NH_2\) is a stronger base than \((CH_3)_3N\) in aqueous solution?

Write structural formulae of the compound A and B:
\(CH_3CONH_2 \xrightarrow{NaOBr} A \xrightarrow[Base]{C_6H_5COCl} B\)

A compound ‘X’ with molecular formula \(C_3H_9N\) reacts with Hinsberg reagent to give a product insoluble in alkali. Identify ‘X’.

Why is \(-NH_2\) group of aniline acetylated before carrying out nitration?

Answer the following question :

(b) How can you convert aniline to benzonitrile ?

The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometry of coordination compounds. The Crystal Field Theory (CFT) of coordination compounds is based on the effect of different crystal fields (provided by the ligands taken as point charges), on the degeneracy of d-orbital energies of the central metal atom/ion. The splitting of the d-orbitals provides different electronic arrangements in strong and weak crystal fields. Answer the following questions :

29(a). In octahedral crystal field, energies of which d-orbitals will be raised when ligands approach the central metal atom/ion ? Give reason in support of your answer.

\( [NiCl_4]^{2-} \) is paramagnetic while \( [Ni(CO)_4] \) is diamagnetic though both are tetrahedral. Why? [At. No. Ni=28]

Answer the following question :

(b) Using crystal field theory, write the electronic configuration of central metal atom/ion of the following :

(i) \( \mathrm{[CoF_6]^{3-}} \)

(ii) \( \mathrm{[Co(NH_3)_6]^{3+}} \)

[At. No. : Co = 27]

Answer the following question :

(c) Write hybridization and magnetic behaviour of the complex \( \mathrm{[Fe(CN)_6]^{3-}} \).

[Atomic No. : Fe = 26]

Write the ionic equations for the oxidising action of potassium permanganate for its reaction with \(I^-\) in both acidic and alkaline solutions.

What happens when acidic solution of potassium permanganate is allowed to stand for sometime ? Give the equation involved. What is this type of reaction called ?

From the given data of \(E^{\circ}\) values, answer the following questions :
(I) Why \(E^{\circ}_{M^{2+}/M}\) show irregular trend in the above values ?
(II) Why is \(E^{\circ}_{Cu^{2+}/Cu}\) value exceptionally positive ?
(III) Why \(E^{\circ}_{Mn^{2+}/Mn}\) value is highly negative ?

(b) Answer the following questions:

(i) Name a member of the lanthanoid series

(I) which exhibits +4 oxidation state

(II) which exhibits +2 oxidation state.

(ii) Why transition metals act as good catalyst?

(iii) Why Cr has higher melting point than Mn?

Calculate emf and \(\Delta G\) for the following cell at \(298 \text{ K}\) :
\(Mg(s) / Mg^{2+}(0.01 \text{ M}) // Ag^+(0.001 \text{ M}) / Ag(s)\)
Given : \(E^\circ_{Mg^{2+}/Mg} = -2.37 \text{ V}\), \(E^\circ_{Ag^+/Ag} = +0.80 \text{ V}\)
\([1 \text{ F} = 96500 \text{ C mol}^{-1}, \log 10 = 1]\)

For the reaction :
\(2AgCl(s) + H_2(g) (0.4 \text{ atm}) \rightarrow 2Ag(s) + 2H^+(0.1 \text{ M}) + 2Cl^-(0.2 \text{ M})\)
Calculate emf of the cell at \(25 \text{ } ^\circ\text{C}\).
Given : \(\Delta G^\circ = -43500 \text{ J mol}^{-1}\)
\([\log 10 = 1, 1 \text{ F} = 96500 \text{ C mol}^{-1}]\)

An organic compound (X) has the molecular formula C₅H₁₀O. Draw structures for (X) if it: (I) does not give Tollen's test but gives a positive iodoform test; (II) does not give Tollen's test and iodoform test but undergoes Aldol condensation; (III) undergoes Cannizzaro's reaction.

Show how each of the following compounds can be converted to benzoic acid: (I) Acetophenone; (II) Ethyl benzene.