CBSE Class 12 2025 Chemistry 56-4-2 Question Paper Set-2: Download Solutions with Answer Key

Alkenes are formed by heating alcohols with conc. \(H_2SO_4\). The first step in the reaction is:

• (A) formation of carbocation
• (B) formation of ester
• (C) protonation of alcohol molecule
• (D) elimination of water

Polyhalogen compounds have wide application in industries and agriculture. DDT is also a very important polyhalogen compound. It is a:

• (A) greenhouse gas
• (B) fertilizer
• (C) biodegradable insecticide
• (D) non-biodegradable insecticide

The product of the oxidation of \(I^–\) with \(MnO_4^–\) in alkaline medium is:

• (A) \(IO_4^-\)
• (B) \(I_2\)
• (C) \(IO^–\)
• (D) \(IO_3^–\)

In the given reaction sequence, the structure of Y would be:

Out of 2-Bromobutane, 1-Bromobutane, 2-Bromopropane and 1-Bromopropane, the molecule which is chiral in nature is:

• (A) 2-Bromobutane
• (B) 1-Bromobutane
• (C) 2-Bromopropane
• (D) 1-Bromopropane

In the Haworth structure of the following carbohydrate, various carbon atoms have been numbered. The anomeric carbon is numbered as:

• (A) 1
• (B) 2
• (C) 3
• (D) 5

The value of Henry’s constant \( K_H \) is:

• (A) greater for gases with higher solubility
• (B) greater for gases with lower solubility
• (C) constant for all gases
• (D) not related to the solubility of gases

Out of the following statements, the \textbf{incorrect} statement is:

• (A) La is actually an element of transition series.
• (B) Zr and Hf have almost identical atomic radii because of lanthanoid contraction.
• (C) Ionic radius decreases from \(La^{3+}\) to \(Lu^{3+}\) ion.
• (D) Lanthanoids are radioactive in nature.

In an electrochemical cell, the following reaction takes place:

2Ag+ (aq) + Mg (s) → 2Ag (s) + Mg2+ (aq)

E\(_cell\) = 2.96 V

As the reaction progresses, what will happen to the overall voltage of the cell?

• (A) Voltage will remain constant.
• (B) It will decrease as [Mg2+] increases.
• (C) It will increase as [Ag+] increases.
• (D) It will increase as [Mg2+] increases.

Out of Ti3+, Cr3+, Mn2+ and Ni2+ ions, the one which has the highest magnetic moment is:

• (A) Ti3+
• (B) Cr3+
• (C) Mn2+
• (D) Ni2+

Hofmann Bromamide degradation reaction is given by:

• (A) \(CH_{3}NO_{2}\)
• (B) \(CH_{3}NH_{2}\)
• (C) \(CH_{3}CONH_{2}\)
• (D) \(CH_{3}CH_{2}NH_{2}\)

What amount of electric charge is required for the oxidation of 1 mole of $H_2O$ to $O_2$?

• (A) 1F
• (B) 2F
• (C) 3F
• (D) 4F

Assertion (A): Cuprous salts are diamagnetic.

Reason (R): In cuprous ion, 3d-orbitals are partially filled.

Assertion (A): Acetanilide is more basic than aniline.

Reason (R): Acetylation of aniline results in decrease of electron density on nitrogen.

Assertion (A): Electrolysis of aqueous NaCl gives \(H_2\) at cathode and \(Cl_2\) at anode.

Reason (R): Chlorine has higher oxidation potential than \(H_2O\).

Assertion (A): n-Butyl chloride has higher boiling point than n-Butyl bromide.

Reason (R): C–Cl bond is more polar than C–Br bond.

What is meant by essential amino acids? Why are amino acids amphoteric in nature?

(a) Reactant ‘A’ underwent a decomposition reaction. The concentration of ‘A’ was measured periodically and recorded in the table given below:
 

(b) The reaction between \(H_2\) (g) and \(I_2\) (g) was carried out in a sealed isothermal container. The rate law for the reaction was found to be:

\[ \text{Rate} = k[H_2][I_2] \]

If 1 mole of \(H_2\) (g) was added to the reaction chamber and the temperature was kept constant, then predict the change in rate of the reaction and the rate constant.

\(PtCl_4 2KCl\) doesn’t give precipitate of \(AgCl\) with \(AgNO_3\) solution. Write the structural formula and IUPAC name of the complex.

Define fuel cell. Give two advantages of fuel cell over ordinary cell.

Write the structures of the main products of the following reactions:




(a) 6 R–COOH + 2Al \(\rightarrow\)

(a) Can sodium methoxide and t-butyl bromide be used for the preparation of t-butyl methyl ether? Give suitable reason. Justify your answer by suggesting the appropriate starting material if required for the preparation of t-butyl methyl ether.

(b) Give the IUPAC name of the above mentioned ether.

Arrange the following compounds as asked:


(a) In increasing order of pK\(_{\text{b}}\) values: \( \text{C}_2\text{H}_5\text{NH}_2 \), \( (\text{C}_2\text{H}_5)_2\text{NH} \), \( \text{C}_6\text{H}_5\text{NHCH}_3 \), \( \text{C}_6\text{H}_5\text{NH}_2 \)

Calculate the cell voltage of the voltaic cell which is set up by joining the following half-cells at 25°C:

\( \text{Al}/\text{Al}^{3+} (0.001 \, \text{M}) \) and \( \text{Ni}/\text{Ni}^{2+} (0.001 \, \text{M}) \)

Given: \( E^0_{\text{Ni}^{2+}/\text{Ni}} = -0.25 \, \text{V} \), \( E^0_{\text{Al}^{3+}/\text{Al}} = -1.66 \, \text{V} \)

Account for the following:

(i) Allyl chloride is hydrolysed more readily than n-propyl chloride.

Complete the following reactions by writing the structural formulae of ‘A’ and ‘B’:


(i) \[ \text{CH}_3\text{CH}=\text{CH}_2 \xrightarrow{\text{HBr, Peroxide}} \text{‘A’} \xrightarrow{\text{aq. KOH}} \text{‘B’} \]


(ii) \[ \text{CH}_3\text{CH}_2\text{CH(Cl)CH}_3 \xrightarrow{\text{alc. KOH, } \Delta} \text{‘A’} \xrightarrow{\text{HBr}} \text{‘B’} \]


(iii) \[ \text{‘A’} \xrightarrow{\text{Mg}} \text{CH}_3\text{CH}_2\text{CH}_2\text{MgCl} \xrightarrow{\text{H}_2\text{O, H}^+} \text{‘B’ (Main product)} \]

Give explanation for each of the following observations:


(a) \( \text{Mn}^{3+} \) is an oxidising agent, whereas \( \text{Cr}^{2+} \) is a reducing agent (both \( \text{d}^4 \) configuration).

An aqueous solution of NaOH was made and its molar mass from the measurement of osmotic pressure at 27°C was found to be \( 25 \, \text{g mol}^{-1} \). Calculate the percentage dissociation of NaOH in this solution.

A compound ‘A’ with molecular formula \( \text{C}_4\text{H}_8\text{O} \) gives positive 2,4-DNP test. It gives yellow precipitate of compound ‘B’ on treatment with sodium hydrogen sulphite. Compound ‘A’ does not react with Tollen’s or Fehling’s reagent; on oxidation with \( \text{KMnO}_4 \), it forms carboxylic acid ‘C’. Elucidate the structures of ‘A’, ‘B’ and ‘C’. Also give their IUPAC names.

The initial concentration of \( \text{N}_2\text{O}_5 \) in the first order reaction:
\[ \text{N}_2\text{O}_5 (\text{g}) \rightarrow 2\text{NO}_2 (\text{g}) + \frac{1}{2} \text{O}_2 (\text{g}) \]
was \( 1.2 \times 10^{-2} \, \text{mol L}^{-1} \). The concentration of \( \text{N}_2\text{O}_5 \) after 60 minutes was \( 0.2 \times 10^{-2} \, \text{mol L}^{-1} \). Calculate the rate constant of the reaction at 318 K.
[log 6 = 0.778]

Complete the following reactions by writing the structure of the main products:






(I)
\(C(=O)-NHNH_2 + H_{2}NCONHNH_{2}\) \(\rightarrow\)

Give simple chemical test to distinguish the following pairs of compounds:


(I) Ethyl benzoate and benzoic acid

Complete each synthesis by giving missing starting material, reagent or products:






(I) \(Ph-CH_2CH_3\) \(\Rightarrow\)(i) \(KMnO_4, KOH\)
(ii) \(H_3O^+\) ?

Carry out the following conversions:


(I) Benzaldehyde to Benzophenone

Give reasons:


(I) \( [\text{Ni}(\text{CO})_4] \) is diamagnetic whereas \( [\text{NiCl}_4]^{2-} \) is paramagnetic.

Using Crystal Field Theory, write the number of unpaired electrons in octahedral complexes of \( \text{Fe}^{3+} \) in the presence of:


(I) Strong field ligand

Name the type of isomerism exhibited and draw isomers:


(I) \( [\text{Co}(\text{NH}_3)_6][\text{Cr}(\text{CN})_6] \)

Differentiate between weak field and strong field ligands. How does the strength of the ligand influence the spin of the complex?