CBSE Class 12 Chemistry Question Paper 2025 with Solutions Set 1 ( Available)- Download PDF

In case of association, abnormal molar mass of solute will:

• (A) increase
• (B) decrease
• (C) remain same
• (D) first increase and then decrease

Standard electrode potential for Sn\(^{4+}\)/Sn\(^{2+}\) couple is +0.15 V and that for the Cr\(^{3+}\)/Cr couple is -0.74 V. The two couples in their standard states are connected to make a cell. The cell potential will be:

• (A) +1.19 V
• (B) +0.89 V
• (C) +0.18 V
• (D) +1.83 V

The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of Cr\(^{3+}\) ion (Atomic no. : Cr = 24) is:

• (A) 2.87 B.M.
• (B) 3.87 B.M.
• (C) 3.47 B.M.
• (D) 3.57 B.M.

Acidified KMnO\(_4\) oxidizes sulphite to:

• (A) SO\(_3^{2-}\)
• (B) SO\(_4^{2-}\)
• (C) SO\(_2\)(g)
• (D) S\(_2\)O\(_8^{2-}\)

The correct IUPAC name of [Pt(NH\(_3\))\(_2\)Cl\(_2\)]\(^{2+}\) is:

• (A) Diamminedichloridoplatinum (II)
• (B) Diamminedichloridoplatinum (IV)
• (C) Diamminedichloridoplatinum (O)
• (D) Diamminedichloridoplatinate (IV)

Arrange the following compounds in increasing order of their boiling points:

• (A) (ii) \(<\) (i) \(<\) (iii)
• (B) (i) \(<\) (ii) \(<\) (iii)
• (C) (iii) \(<\) (i) \(<\) (ii)
• (D) (iii) \(<\) (ii) \(<\) (i)

Alkyl halides undergoing nucleophilic bimolecular substitution reaction involve:

• (A) retention of configuration
• (B) formation of racemic mixture
• (C) inversion of configuration
• (D) formation of carbocation

Which is the correct order of acid strength from the following?

• (A) C\(_6\)H\(_5\)OH \(>\) H\(_2\)O \(>\) ROH
• (B) C\(_6\)H\(_5\)OH \(>\) ROH \(>\) H\(_2\)O
• (C) ROH \(>\) C\(_6\)H\(_5\)OH \(>\) H\(_2\)O
• (D) H\(_2\)O \(>\) C\(_6\)H\(_5\)OH \(>\) ROH

The acid formed when propyl magnesium bromide is treated with CO\(_2\) followed by acid hydrolysis is:

• (A) C\(_3\)H\(_7\)COOH
• (B) C\(_2\)H\(_5\)COOH
• (C) CH\(_3\)COOH
• (D) C\(_3\)H\(_7\)OH

The best reagent for converting propanamide into propanamine is:

• (A) excess H\(_2\)
• (B) Br\(_2\) in aqueous NaOH
• (C) iodine in the presence of red phosphorus
• (D) LiAlH\(_4\) in ether

Which of the following statements is not true about glucose?

• (A) It is an aldose.
• (B) On heating with HI it forms n-hexane.
• (C) It exists in furanose form.
• (D) It does not give Schiff's test.

An unripe mango placed in a concentrated salt solution to prepare pickle, shrivels because __________

• (A) it gains water due to osmosis
• (B) it loses water due to reverse osmosis
• (C) it gains water due to reverse osmosis
• (D) it loses water due to osmosis

Assertion (A): [Cr(H\(_2\)O)\(_6\)]Cl\(_2\) and [Fe(H\(_2\)O)\(_6\)]Cl\(_2\) are examples of homoleptic complexes.

Reason (R): All the ligands attached to the metal are the same.

• (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 boiling points of alkyl halides decrease in the order: RI \(>\) RBr \(>\) RCl \(>\) RF.

Reason (R): The boiling points of alkyl chlorides, bromides and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.

• (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 boiling point of ethanol is higher than that of methoxymethane.

Reason (R): There is intramolecular hydrogen bonding in ethanol.

• (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): All naturally occurring \(\alpha\)-amino acids except glycine are optically active.

Reason (R): Most naturally occurring amino acids have L-configuration.

• (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.

(A) Give reasons:

(a) Cooking is faster in a pressure cooker than in an open pan.

(b) On mixing liquid X and liquid Y, volume of the resulting solution decreases. What type of deviation from Raoult's law is shown by the resulting solution? What change in temperature would you observe after mixing liquids X and Y?

(B) Define Azeotrope. What type of Azeotrope is formed by negative deviation from Raoult's law? Give an example.

Complete and balance the following chemical equations:

(a) \[ 2MnO_4^-(aq) + 10I^-(aq) + 16H^+(aq) \rightarrow \]

(b) \[ Cr_2O_7^{2-}(aq) + 6Fe^{2+}(aq) + 14H^+(aq) \rightarrow \]

Would you expect benzaldehyde to be more reactive or less reactive in nucleophilic addition reactions than propanal? Justify your answer.

Identify A and B in each of the following reaction sequence:

(a) \[ CH_3CH_2Cl \xrightarrow{NaCN} A \xrightarrow{H_2/Ni} B \]

(b) \[ C_6H_5NH_2 \xrightarrow{NaNO_2/HCl} A \xrightarrow{C_6H_5NH_2} B \]

Write the reactions involved when D-glucose is treated with the following reagents:

(a) HCN
(b) Br\(_2\) water

A solution of glucose (molar mass = 180 g mol\(^{-1}\)) in water has a boiling point of 100.20°C. Calculate the freezing point of the same solution. Molal constants for water \(K_f\) and \(K_b\) are 1.86 K kg mol\(^{-1}\) and 0.512 K kg mol\(^{-1}\) respectively.

(a) State the following:

(i) Kohlrausch law of independent migration of ions

(ii) Faraday’s first law of electrolysis

(b) Using \( E^\circ \) values of X and Y given below, predict which is better for coating the surface of iron to prevent corrosion and why?

Given: \( E^\circ_{X^{2+}/X} = -2.36 \, V \) \( E^\circ_{Y^{2+}/Y} = -0.14 \, V \) \( E^\circ_{Fe^{2+}/Fe} = -0.44 \, V \)

A certain reaction is 50 complete in 20 minutes at 300 K and the same reaction is 50 complete in 5 minutes at 350 K. Calculate the activation energy if it is a first order reaction.

Given: \[ R = 8.314 \, J K^{-1} \, mol^{-1}, \quad \log 4 = 0.602 \]

The elements of 3d transition series are given as: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn
Answer the following:

(a) Copper has an exceptionally positive \( E^\circ_{M^{2+}/M} \) value, why?

(b) Which element is a strong reducing agent in +2 oxidation state and why?

(c) Zn\(^{2+}\) salts are colourless. Why?

(A) Draw the structure of the major monohalo product for each of the following reactions:

(a)

(a) Chlorobenzene to biphenyl

(b) Propene to 1-Iodopropane

(c) 2-Bromobutane to but-2-ene

(a) Arrange the following compounds in increasing order of their boiling point:
\[ (CH_3)_2NH, CH_3CH_2NH_2, CH_3CH_2OH \]

(i) Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.

(ii) Amides are less basic than amines.

(a) What is the difference between native protein and denatured protein?

(b) Which one of the following is a disaccharide? \[ Glucose, Lactose, Amylose, Fructose \]

(c) Which vitamin is responsible for the coagulation of blood?

(i) What is a rate determining step?

(ii) Define complex reaction.

What is the effect of temperature on the rate constant of a reaction?

Why is molecularity applicable only for elementary reactions whereas order is applicable for elementary as well as complex reactions?

(c) The conversion of molecule X to Y follows second-order kinetics. If the concentration of X is increased 3 times, how will it affect the rate of formation of Y?

(i) Br\(_2\)/CS\(_2\)

(ii) Conc. HNO\(_3\)

(b) Why phenol does not undergo protonation readily?

(c) Which is a stronger acid – phenol or cresol? Give reason.

(c) Write the IUPAC name of the product formed in the Reimer-Tiemann reaction.

(a) Write the cell reaction and calculate the e.m.f. of the following cell at 298 K:
\[ Sn(s) \mid Sn^{2+} (0.004 M) \parallel H^+ (0.02 M) \mid H_2 (1 Bar) \mid Pt(s) \]

(Given: \( E^\circ_{Sn^{2+}/Sn} = -0.14 \, V, E^\circ_{H^+/H_2} = 0.00 \, V \))

(i) On the basis of \( E^\circ \) values, O\(_2\) gas should be liberated at anode but it is Cl\(_2\) gas which is liberated in the electrolysis of aqueous NaCl.

(ii) Conductivity of CH\(_3\)COOH decreases on dilution.

(a.)Write the anode and cathode reactions and the overall cell reaction occurring in a lead storage battery during its use.

(b.)Calculate the potential for half-cell containing 0.01 M K\(_2\)Cr\(_2\)O\(_7\)(aq), 0.01 M Cr\(^{3+}\)(aq), and 1.0 x 10\(^{-4}\) M H\(^+\)(aq).

(a) Low spin tetrahedral complexes are not known.

(b) Co\(^{2+}\) is easily oxidized to Co\(^{3+}\) in the presence of a strong ligand (At. No. of Co = 27).

(c) What type of isomerism is shown by the complex [Co(NH₃)₆][Cr(CN)₆]?

(d) Why is a solution of Ni(H₂O)₆²⁺ green while a solution of Ni(CN)₄²⁻ is colourless? (At. No. of Ni = 28)

(e) Write the IUPAC name of the following complex: [Co(NH₃)₅(CO₃)]Cl.

(i) Ethanal to But-2-enal

(ii) Propanoic acid to Ethane

(b) An alkene A with molecular formula C\(_6\)H\(_{10}\) on ozonolysis gives a mixture of two compounds B and C. Compound B gives positive Fehling test and also reacts with iodine and NaOH solution. Compound C does not give Fehling solution test but forms iodoform. Identify the compounds A, B, and C.