List of top Questions asked in CBSE CLASS XII- 2026

Explain with the help of Henry's law: (i) Bends (ii) Anoxia
Write the formulas of: (a) Mercury(I) tetrathiocyanato-S-cobaltate(III)
(b) Dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate
Which reagent is used to convert benzene diazonium chloride to benzene?
Assertion (A): Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
Reason (R): Diazonium salts of aromatic amines undergo resonance.
Consider the cell at 298 K: $Mg(s)|Mg^{2+}(1.0M)||Cu^{2+}(1.0M)|Cu(s)$. How can we increase the emf of the cell using the same substances?
Which of the following is a water-soluble vitamin?
Assertion (A): Alcohols act as Bronsted bases as well as Bronsted acids.
Reason (R): Alcohols react as both nucleophiles and electrophiles.
Assertion (A): For complex reactions, order of reaction is given by the fast step.
Reason (R): Order of reaction is determined experimentally.
Number of possible stereoisomers for the complex $[Co(en)_2Cl_2]Cl$ will be:
The rate of a first-order reaction is $5.6 \times 10^{-4}$ mol L$^{-1}$s$^{-1}$ when the concentration of reactant is $0.2$ mol L$^{-1}$. The rate constant $k$ is:
The correct order of decreasing basic strength of $CH_3NH_2$, $(CH_3)_2NH$ and $(CH_3)_3N$ in aqueous solution is:
The boiling point of one molal NaCl solution, assuming NaCl to be completely dissociated in water, is: ($K_b = 0.52$ K kg mol$^{-1}$)
When a liquid and its vapour are at equilibrium and the pressure is suddenly decreased:
Williamson synthesis is an example of:
Which property of transition metals enables them to form alloys?
Which of the following d-orbitals experience more repulsion in the crystal field splitting of a tetrahedral complex?
The position of $-$Br in the compound shown (a vinyl bromide structure) can be classified as:
Write the mechanism of acid dehydration of ethanol to yield ethene.
Why is ortho-nitrophenol more acidic than ortho-methoxyphenol?
Consider the decomposition of hydrogen peroxide \((H_{2}O_{2})\) as per the equation given below: \[ 2H_{2}O_{2} \overset{I^-}{\longrightarrow} 2H_{2}O + O_{2} \] The mechanism for this reaction was found to be: \[ \textbf{Step I:}\qquad H_{2}O_{2}+I^- \longrightarrow H_{2}O+IO^- \qquad (\text{slow}) \] \[ \textbf{Step II:}\qquad H_{2}O_{2}+IO^- \longrightarrow H_{2}O+I^-+O_{2} \qquad (\text{fast}) \] (a) Write the rate law expression.
Calculate the vapour pressure of a solution containing \( 61 \, g \) of benzoic acid (molar mass \( = 122 \, g \, mol^{-1} \)) dissolved in \( 500 \, g \) of benzene when the vapour pressure of pure benzene at this temperature of experiment is \( 66 \, torr \). Assume complete dimerization of benzoic acid in benzene.
What is the molecularity of the reaction in Step II?
Which isomer of \( C_4H_9Br \) is most reactive towards \( S_N1 \) reaction?
Although chlorine shows strong \( -I \) effect, yet it is ortho- and para-directing in electrophilic aromatic substitution reactions. Why?
Determine the order of reaction with respect to \( H_2O_2 \), \( I^- \) and overall order of reaction.