List of top Questions asked in CBSE CLASS XII

Why Zinc is not regarded as a transition element?
Why is first ionization enthalpy of chromium lower than that of Zn?
Predict whether \([CoF_6]^{3-}\) is diamagnetic or paramagnetic and why?
\([Atomic \ \ number : Co = 27]\)
Show that the time required for 99.9% completion in a first-order reaction is 10 times of half-life (t$_{1/2}$) of the reaction.
What happens when ethyl chloride is treated with alcoholic potassium hydroxide?
Give chemical tests to distinguish between the following pairs of compounds:
(i) Phenol and Benzoic acid:
(ii) Propanal and Propanone:
Explain the following terms:
(a) Essential amino acids:
(b) Peptide bond:
(c) Denaturation:
Write chemical equations for the following reactions:
(a) Hydroboration – Oxidation reaction:
(b) Williamson Synthesis:
(c) Friedel-Crafts Alkylation of Anisole:
(d) Reimer-Tiemann Reaction:
The presence of –NO$_2$ group at ortho or para position increases the reactivity of haloarenes towards nucleophilic substitution reactions. Give reason to explain the above statement.
What is meant by a unidentate ligand? Give an example.
Write the IUPAC name of the given compound:
3– Bromo– 1 chlorocyclohexene
Which one of the given compounds is a stronger acid and why?
CH$_2$FCH$_2$COOH or CH$_3$CHFCH$_2$COOH
Calculate emf of the following cell at 25°C:
Sn/Sn$^{2+}$(0.001 M) || H$^+$(0.01 M) | H$_2$(g)(1 bar) | Pt(s)
Given: E°(Sn$^{2+}$/Sn) = -0.14 V, E° H$^+$/H$_2$ = 0.00 V (log 10 = 1)
How will you convert the following?
(i) Toluene to Benzoic acid:
(ii) Ethanol to 3-Hydroxybutanal:
What happens when glucose reacts with bromine water? Write the chemical equation.
18 g of a non-volatile solute is dissolved in 200 g of H$_2$O, and it freezes at 272.07 K. Calculate the molecular mass of the solute (K$_f$ for water = 1.86 K kg mol$^{-1}$).
Arrange the following compounds in the increasing order of their boiling points:
Butane, 1-Bromobutane, 1-Iodobutane, 1-Chlorobutane
Which compound in the given pair will undergo S$_N$2 reaction at a faster rate and why?
CH$_3$–CH$_2$–I and CH$_3$–CH$_2$–Br
Write the stepwise mechanism of nucleophilic addition reactions in the carbonyl compounds.
Write the electronic configuration for d$^4$ ion if \( \Delta_0 < P \) on the basis of crystal field theory.
Define the following terms:
(a) Order of Reaction:
(b) Activation Energy:
Assertion (A): Fructose is a reducing sugar.
Reason (R): Fructose does not reduce Fehling solution and Tollen’s reagent.
Assertion (A): Benzoic acid does not undergo Friedel – Crafts reaction.
Reason (R): Carboxyl group is deactivating and the catalyst aluminium chloride gets bonded to the carboxyl group.
Assertion (A): For a Daniell cell, Zn/Zn$^{2+}$(1M) || Cu$^{2+}$(1M)/Cu with \( E_{\text{cell}} = 1.1 \, V \), if the external opposing potential is more than 1.1 V, the electrons flow from Cu to Zn.
Reason (R): Cell acts like a galvanic cell.
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.