List of top Questions asked in CBSE CLASS XII- 2024

If \(\begin{bmatrix} a & c & 0 \\ b & d & 0 \\ 0 & 0 & 5 \end{bmatrix}\)is a scalar matrix, then the value of \( a + 2b + 3c + 4d \) is: 
 
If \( A \) and \( B \) are two skew-symmetric matrices, then \( AB + BA \) is:
If \(A = \begin{bmatrix} 2 & 1 \\ -4 & -2 \end{bmatrix}\), then the value of \( I - A + A^2 - A^3 + \ldots \) is: 
 
If \(A = [a_{ij}] = \begin{bmatrix} 2 & -1 & 5 \\ 1 & 3 & 2 \\ 5 & 0 & 4 \end{bmatrix}\) and \( c_{ij} \) is the cofactor of element \( a_{ij} \), then the value of \( a_{21}c_{11} + a_{22}c_{12} + a_{23}c_{13} \) is:
Anisole reacts with HI to give:
Which of the following alkyl halides will undergo S$_N$1 reaction most readily?
Write the stepwise mechanism of nucleophilic addition reactions in the carbonyl compounds.
The following initial rate data were obtained for the reaction: \[ 2\text{NO (g)} + \text{Br}_2 \text{(g)} \rightarrow 2 \text{NOBr (g)} \] initial rate data were obtained for the reaction
An azeotropic solution of two liquids has a boiling point lower than either of them when it:
The relative lowering of vapor pressure of an aqueous solution containing a non-volatile solute is 0.0225. The mole fraction of the non-volatile solute is:
Phenol dimerises in benzene having van’t Hoff factor 0.54. Its degree of association is:
A 1% solution of solute ‘X’ is isotonic with a 6% solution of sucrose (molar mass = \( 342 \) g mol\(^{-1}\)). The molar mass of solute ‘X’ is:
Assertion (A): When NaCl is added to water, elevation in boiling point is observed. Reason (R): Elevation in boiling point is a colligative property.
Assertion (A): p-Nitroaniline is a weaker base than p-toluidine. Reason (R): The electron-withdrawing effect of \(-NO_2\) group in p-nitroaniline makes it a weaker base.
Phenol does not undergo nucleophilic substitution reaction easily due to:
Which of the following compounds will not react with benzene sulphonyl chloride?
 
Aniline on reaction with Bromine water gives:
Assertion (A): Aliphatic primary amines can be prepared by Gabriel phthalimide synthesis. Reason (R): Alkyl halides undergo nucleophilic substitution with anion formed by phthalimide.
Assertion (A): Diazonium salts of aromatic amines are more stable than those of aliphatic amines. Reason (R): Diazonium salts of aliphatic amines show resonance.
Identify the tertiary amine from the following:
Dehydration of tertiary alcohols with Cu at 573 K gives:
Ethanol on heating with conc. H\(_2\)SO\(_4\) at 413 K gives:
Phenol on reaction with aqueous bromine at room temperature gives:
Consider the following reaction:
benzyl alcohol (C6H5CH2OH)
The major product obtained is:
Assertion (A): p-nitrophenol is less acidic than phenol.
Reason (R): Nitro group is electron-withdrawing and helps in the stabilization of p-nitrophenoxide ion.