CBSE 2025, Set 2 Solutions
CBSE Chemistry (2025)

Assertion (A): Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.

Reason (R): Aryl halides do not undergo nucleophilic substitution reaction with the anion formed by phthalimide.

Assertion (A): Cu cannot liberate H$_2$ on reaction with dilute mineral acids.

Reason (R): Cu has positive electrode potential.

Assertion (A): In a first order reaction, if the concentration of the reactant is doubled, its half-life is also doubled.

Reason (R): The half-life of a first order reaction does not depend upon the initial concentration of the reactant.

Scurvy is caused due to deficiency of

Nucleotides are joined together by

The conversion of phenol to salicylic acid can be accomplished by

What will be formed after oxidation reaction of secondary alcohol with chromic anhydride (CrO$_3$)?

Which is the correct IUPAC name for the following compound?

The diamagnetic species is : [At. No. Co = 27, Fe = 26, Ni = 28]

The complex ions $[\text{Co(NH}_3)_5(\text{NO}_2)]^{2+}$ and $[\text{Co(NH}_3)_5(\text{ONO})]^{2+}$ are called

The element having [Ar]3d$^{10}$4s$^1$ electronic configuration is

The number of molecules that react with each other in an elementary reaction is a measure of the

The charge required for the reduction of 1 mol of MnO$_4^-$ to MnO$_2$ is

In the following pair of halogen compounds, which compound undergoes S$_N$1 reaction faster and why?

Arrange the following compounds in increasing order of their reactivity towards S$_N$2 displacement:

2-Bromo-2-methylbutane, 1-Bromopentane, 2-Bromopentane

A reaction is of second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is (i) doubled (ii) reduced to half?

When FeCr$_2$O$_4$ is fused with Na$_2$CO$_3$ in the presence of air it gives a yellow solution of compound (A). Compound (A) on acidification gives compound (B). Compound (B) on reaction with KCl forms an orange coloured (C). An acidified solution of compound (C) oxidises Na$_2$SO$_3$ to (D). Identify (A), (B), (C) and (D).

Explain $[\text{Co(NH}_3)_6]^{3+}$ is an inner orbital complex whereas $[\text{Ni(NH}_3)_6]^{2+}$ is an outer orbital complex. [At. No. Co = 27, Ni = 28]

The rate constant for a zero order reaction A $\rightarrow$ P is 0.0030 mol L$^{-1}$s$^{-1}$. How long will it take for the initial concentration of A to fall from 0.10 M to 0.075 M?

The decomposition of NH$_3$ on platinum surface is zero order reaction. What are the rates of production of N$_2$ and H$_2$ if k = 2.5 × 10$^{-4}$ mol L$^{-1}$ s$^{-1}$?

A solution containing 15 g urea (molar mass = 60 g mol$^{-1}$) per litre of solution in water has the same osmotic pressure (isotonic) as a solution of glucose (molar mass = 180 g mol$^{-1}$) in water. Calculate the mass of glucose present in one litre of its solution.

Calculate $\Lambda°_m$ for acetic acid and its degree of dissociation ($\alpha$) if its molar conductivity is 48.1 $\Omega^{-1}$ cm$^2$ mol$^{-1}$.

Given: $\Lambda°_m$ (HCl) = 426 $\Omega^{-1}$ cm$^2$ mol$^{-1}$ $\Lambda°_m$ (NaCl) = 126 $\Omega^{-1}$ cm$^2$ mol$^{-1}$ $\Lambda°_m$ (CH$_3$COONa) = 91 $\Omega^{-1}$ cm$^2$ mol$^{-1}$

Of the d$^4$ species, Cr$^{2+}$ is strongly reducing while Mn$^{3+}$ is strongly oxidising. Why?

Write two consequences of lanthanoid contraction.

Which element of the 3d series has the lowest enthalpy of atomisation and why?

Write IUPAC names of the following coordination entities:

(a) $[\text{Fe(en)}_2\text{Cl}_2]^+$

(b) $[\text{Co(NH}_3)_4(\text{H}_2\text{O})\text{Br}]\text{SO}_4$

(c) $[\text{Ni(CN)}_4]^{2-}$

Explain the following reactions and write the chemical equation involved:

(a) Wolff-Kishner reduction

(b) Etard reaction

(c) Cannizzaro reaction

Write the structures of A, B and C in the following sequence of reactions:

$\text{CH}_3\text{COOH} \xrightarrow{\text{SOCl}_2} A \xrightarrow{\text{H}_2,\,\text{Pd-BaSO}_4} B \xrightarrow{\text{H}_2\text{N–NH}_2} C$

Write the structures of A, B and C in the following sequence of reactions:

$\text{CH}_3\text{CN} \xrightarrow{1.\,\text{DIBAL-H}} \xrightarrow{2.\,\text{H}_2\text{O}} A \xrightarrow{\text{dil. NaOH}} B \xrightarrow{\Delta} C$

Define the following:

(i) Enantiomers

(ii) Racemic mixture

Why is chlorobenzene resistant to nucleophilic substitution reaction?

Write the product obtained when D-glucose reacts with H$_2$N–OH.

Amino acids show amphoteric behaviour — why?

Read the passage and answer:

Amines have a lone pair of electrons on nitrogen atom due to which they behave as Lewis base. Greater the value of K$_b$ or smaller the value of pK$_b$, stronger is the base. Amines are more basic than alcohols, ethers, esters, etc. The basic character of aliphatic amines should increase with the increase of alkyl substitution. But it does not occur in a regular manner as a secondary aliphatic amine is unexpectedly more basic than a tertiary amine in aqueous solutions. Aromatic amines are weaker bases than ammonia and aliphatic amines. Electron releasing groups such as –CH₃, –OCH₃, –NH₂ etc., increase the basicity while electron-withdrawing substituents such as –NO₂, –CN, halogens etc., decrease the basicity of amines.

(a) Arrange the following in the increasing order of their basic character. Give reason:

(b) Why is pK$_b$ of aniline more than that of methylamine?

Read the passage and answer:

The spontaneous flow of the solvent through a semipermeable membrane from a pure solvent to a solution or from a dilute solution to a concentrated solution is called osmosis. Reverse osmosis takes place when the applied external pressure becomes larger than the osmotic pressure.

(a) Define reverse osmosis. Name one semipermeable membrane (SPM) which can be used in the process of reverse osmosis.

An organic compound 'A', molecular formula C$_2$H$_6$O oxidises with CrO$_3$ to form a compound 'B'. Compound 'B' on warming with iodine and aqueous solution of NaOH gives a yellow precipitate of compound 'C'. When compound 'A' is heated with conc. H$_2$SO$_4$ at 413 K gives a compound 'D', which on reaction with excess HI gives compound 'E'. Identify compounds 'A', 'B', 'C', 'D' and 'E' and write chemical equations involved.

Write chemical equations of the following reactions:

(i) Phenol is treated with conc. HNO$_3$

(ii) Propene is treated with B$_2$H$_6$ followed by oxidation by H$_2$O$_2$/OH$^-$

(iii) Sodium t-butoxide is treated with CH$_3$Cl

Give a simple chemical test to distinguish between butan-1-ol and butan-2-ol.

Arrange the following in increasing order of acid strength: phenol, ethanol, water

Give IUPAC name of CH$_3$–CH=CH–CHO.

Give a simple chemical test to distinguish between propanal and propanone.

How will you convert the following:

(i) Toluene to benzoic acid

(ii) Ethanol to propan-2-ol

(iii) Propanal to 2-hydroxypropanoic acid

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

(a) Cyclopentanone + HO–NH₂ → ?

(b) ? + (i) O₃, (ii) Zn–H₂O → 2 × cyclopentanone

(c) Cyclohexane-1,2-dicarboxylic acid + SOCl₂ → ?

(d) A compound with both CHO and COOH groups on cyclohexane + NaCN/HCl → ?

(e) Benzene → acetophenone (phenyl methyl ketone) using what reagent?

(a) Calculate the standard Gibbs energy ($\Delta_r G°$) of the following reaction at 25°C:

$\text{Au(s)} + \text{Ca}^{2+}(1\text{M}) \rightarrow \text{Au}^{3+}(1\text{M}) + \text{Ca(s)}$

$E°_{\text{Au}^{3+}/\text{Au}} = +1.5 \text{ V},\quad E°_{\text{Ca}^{2+}/\text{Ca}} = -2.87 \text{ V}$

Predict whether the reaction will be spontaneous or not at 25°C.

[1 F = 96500 C mol$^{-1}$]

Define the following:

(i) Cell potential

(ii) Fuel cell

Calculate emf of the following cell at 25°C:

$\text{Zn(s)}\,|\,\text{Zn}^{2+}_{(0.1\text{M})}\,||\,\text{Cd}^{2+}_{(0.01\text{M})}\,|\,\text{Cd(s)}$

Given: $E°_{\text{Cd}^{2+}/\text{Cd}} = -0.40 \text{ V}$, $E°_{\text{Zn}^{2+}/\text{Zn}} = -0.76 \text{ V}$

[log 10 = 1]

Assertion (A): Vitamin D cannot be stored in our body.

Reason (R): Vitamin D is a fat soluble vitamin and is not excreted from the body in urine.

Which of the following is/are examples of denaturation of protein?

Which among the following is a false statement?

Which one of the following will have higher osmotic pressure: 1 M KCl or 1 M urea solution? Justify your answer.

Why is osmotic pressure a colligative property?

What do you expect to happen when red blood corpuscles (RBCs) are placed in 0.5% NaCl solution?

Arrange the following in the increasing order of their basic character in an aqueous solution. Give reason:

$(\text{CH}_3)_3\text{N},\; (\text{CH}_3)_2\text{NH},\; \text{NH}_3,\; \text{CH}_3\text{NH}_2$

Why is the ammonolysis of alkyl halides not considered a good method to prepare pure primary amines?