List of top Questions asked in CBSE CLASS XII- 2026

Find:
Let \(A=[a_{ij}]\) be a \(2\times2\) matrix whose elements are given by \[ a_{ij}=\frac{(2i-j)^2}{3} \] Find the transpose matrix \(A'\).

State any four merits of external sources of recruitment.
What happens when acidic solution of potassium permanganate is allowed to stand for sometime ? Give the equation involved. What is this type of reaction called ?
Write mechanism of acid dehydration of ethanol to ethene.
Predict the alkene that would be formed by dehydrohalogenation of 1-Bromo-1-methylcyclohexane.
Give structures of A, B and C: Aniline $\xrightarrow{Br_2/H_2O}$ A $\xrightarrow{NaNO_2+HCl, 0-5^\circ C}$ B $\xrightarrow{H_3PO_2+H_2O}$ C
Explain: (i) Presence of carbonyl group in glucose. (ii) Presence of five $-$OH groups attached to different carbon atoms.
What are reducing sugars?
Why are magnesium blocks attached to iron water pipelines?
Though chlorine shows strong $-I$ effect, why is it ortho/para directing?
Predict the alkene formed by dehydrohalogenation of 1-Bromo-1-methylcyclohexane.
61 g benzoic acid (M = 122 g mol$^{-1}$) dissolved in 500 g benzene. Vapour pressure of pure benzene = 66 torr. Assume complete dimerisation. Calculate vapour pressure of solution.
For decomposition of $H_2O_2$ by $I^-$: Step I: $H_2O_2 + I^- \rightarrow H_2O + IO^-$ (slow). Step II: $H_2O_2 + IO^- \rightarrow H_2O + I^- + O_2$ (fast). (a) Write rate law. (b) Determine order w.r.t. $H_2O_2$ and $I^-$ and overall order. (c) Molecularity of Step II.
Which isomer of $C_4H_9Br$ is most reactive towards $S_N1$ reaction?
Why are products of electrolysis of $AgNO_3$ different with silver electrodes and platinum electrodes?
Why is DC not used for measuring resistance of ionic solution?
Give structures of A, B and C: $CH_3Cl \xrightarrow{KCN}$ A $\xrightarrow{LiAlH_4}$ B $\xrightarrow{CHCl_3 + \text{alc. } KOH, \Delta}$ C
Under what condition can a bimolecular reaction become kinetically first order?
When $CoCl_3 \cdot 6NH_3$ is mixed with excess $AgNO_3$ solution, 3 moles of $AgCl$ are precipitated per mole. Write its structural formula, IUPAC name, hybridisation and magnetic behaviour (VBT).
Draw the structures of major products: (a) Chlorobenzene + $CH_3Cl$ / Na, dry ether
(b) p-Hydroxyphenethyl alcohol + HBr
What happens when: (a) Propanenitrile is treated with phenyl magnesium bromide followed by hydrolysis? (b) p-Fluorotoluene is treated with $CrO_3$ in presence of acetic anhydride followed by hydrolysis with aqueous acid? (c) Phthalic acid is treated with $NH_3$ followed by heating?
Assertion (A): $E^\circ_{Cu^{2+}/Cu} = +0.34$ V.
Reason (R): It is due to low $\Delta H^\circ_{hyd}$ and high $\Delta H^\circ_a$.
How does sprinkling of salt help in clearing snow-covered roads in hilly areas? Name the colligative property involved.
Write the formulas of: (a) Mercury(I) tetrathiocyanato-S-cobaltate(III)
(b) Dichloridobis(ethane-1,2-diamine)platinum(IV) nitrate
Explain with the help of Henry's law: (i) Bends (ii) Anoxia