List of top Questions asked in CBSE CLASS XII

Rosenmund reduction is used for the preparation of Aldehydes. The catalyst used in this reaction is:
Give reasons for the following:
Methyl amine is more basic than aniline.
Aniline readily reacts with bromine water to give 2, 4, 6-tribromoaniline.
Arrange the following compounds in the increasing order of their basic strength in the gaseous phase:
C$_6$H$_5$NH$_2$, (C$_2$H$_5$)$_3$N, (C$_2$H$_5$)$_2$NH
Primary amines have higher boiling points than tertiary amines.
Calculate the mass of CaCl$_2$ (molar mass = 111 g mol$^{-1}$) to be dissolved in 500 g of water to lower its freezing point by 2K, assuming that CaCl$_2$ undergoes complete dissociation.
Define ideal solution.
Why are aquatic species more comfortable in cold water in comparison to warm water?
Define reverse osmosis.
Predict whether Van’t Hoff factor will be less or greater than one when Ethanoic acid is dissolved in benzene.
A solution containing 2 g of glucose (M = 180 g mol$^{-1}$) in 100 g of water is prepared at 303 K. If the vapour pressure of pure water at 303 K is 32.8 mm Hg, what would be the vapour pressure of the solution?
What is Hinsberg’s reagent?
What is Lanthanoid contraction?
Why are transition elements good catalysts?
Why is first ionization enthalpy of chromium lower than that of Zn?
Why Zinc is not regarded as a transition element?
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.
Predict whether \([CoF_6]^{3-}\) is diamagnetic or paramagnetic and why?
\([Atomic \ \ number : Co = 27]\)
What happens when ethyl chloride is treated with alcoholic potassium hydroxide?
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)
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.
Give chemical tests to distinguish between the following pairs of compounds:
(i) Phenol and Benzoic acid:
(ii) Propanal and Propanone:
Write chemical equations for the following reactions:
(a) Hydroboration – Oxidation reaction:
(b) Williamson Synthesis:
(c) Friedel-Crafts Alkylation of Anisole:
(d) Reimer-Tiemann Reaction:
Write the IUPAC name of the given compound:
3– Bromo– 1 chlorocyclohexene
Explain the following terms:
(a) Essential amino acids:
(b) Peptide bond:
(c) Denaturation: