List of top Questions asked in CBSE CLASS XII- 2026

Why is it necessary to use salt bridge in a galvanic cell?
Why are low spin tetrahedral complexes rarely formed?
\[ \text{What happens when an acidic solution of the green compound }(B)\text{ is allowed to stand for some time? Also write the equation involved. What is this type of reaction called?} \]
\[ \text{Why are }\alpha\text{-hydrogen atoms of aldehydes and ketones acidic in nature?} \]
\[ \text{Arrange the following compounds in increasing order of their reactivity towards }HCN: \]
\[ CH_3COCH_3,\quad CH_3CHO,\quad (CH_3)_3C-CO-CH_3 \]
Write the reaction involved in Etard reaction.
\[ \text{Write the product when cyclohexanecarbaldehyde reacts with }Zn(Hg)/conc.\;HCl. \]
Give reasons for the following:
What is meant by chelate effect? Give an example.
Define Double Salt with one example.
\[ \text{The conductivity of }0.001M\text{ solution of acetic acid is }3.905\times10^{-5}\;S\,cm^{-1}.\text{ Calculate its molar conductivity and degree of dissociation }(\alpha). \]
\[ \lambda^\circ_{CH_3COO^-}=40.9\;S\,cm^2mol^{-1} \]
\[ \lambda^\circ_{H^+}=349.6\;S\,cm^2mol^{-1} \]
Draw the structure of the semicarbazone of acetone.
\[ \text{A black-brown coloured solid }(A)\text{ when fused with }KOH\text{ in the presence of air, produces a dark green compound }(B)\text{ which on electrolytic oxidation in alkaline medium gives a dark purple coloured compound }(C).\text{ Identify }(A),(B)\text{ and }(C).\text{ Write the reactions involved.} \]
Name two coordination compounds which are important in biological systems.
Define Ambidentate Ligand with one example.
The rate of the chemical reaction doubles when the temperature is raised from \(298\,K\) to \(308\,K\). Calculate activation energy \((E_a)\) for this reaction assuming that it does not change with temperature. (Given : \(R = 8.314\,J\,mol^{-1}\,K^{-1}\), \(\log 2 = 0.30\))
Calculate emf of the following cell at \(298\,K\) : \[ Cr(s)\,|\,Cr^{3+}(aq,\;0.1\,M)\,||\,Fe^{2+}(aq,\;0.01\,M)\,|\,Fe(s) \] (Given : \[ E^\circ_{Cr^{3+}/Cr}=-0.74\,V, \] \[ E^\circ_{Fe^{2+}/Fe}=-0.44\,V, \] \[ \log 10 = 1 \] )
Assertion (A) : p-nitrophenol is more acidic than phenol. Reason (R) : Nitro group is an electron-withdrawing group, it stabilises phenoxide ion by dispersal of negative charge.
Assertion (A) : All aliphatic aldehydes give a positive Fehling’s test. Reason (R) : Aliphatic aldehydes are reduced by Fehling’s reagent.
Assertion (A) : Highest oxidation state of Mn is +7 in first series of transition elements. Reason (R) : Transition metals exhibit variable oxidation states.
The polypeptide chain in a protein has amino acids linked with each other in a specific sequence. This specific sequence of amino acids is called :
Identify the polysaccharide among the following :
Assertion (A) : D (+) – Glucose is dextrorotatory in nature. Reason (R) : (+) represents dextrorotatory nature and D represents the configuration.
Consider the following compounds : \[ C_2H_5NH_2,\quad (C_2H_5)_2NH,\quad C_6H_5CH_2NH_2,\quad NH_3,\quad C_6H_5NH_2 \] The correct increasing order of the above compounds on the basis of their basic strength is :
Primary, secondary and tertiary alcohols can be distinguished by :