List of top Chemistry Questions asked in CBSE CLASS XII

Why is a solution of Ni(H₂O)₆²⁺ green while a solution of Ni(CN)₄²⁻ is colourless? (At. No. of Ni = 28)
What type of isomerism is shown by the complex [Co(NH₃)₆][Cr(CN)₆]?
Answer the following:
Co\(^{2+}\) is easily oxidized to Co\(^{3+}\) in the presence of a strong ligand (At. No. of Co = 27).
Answer the following:
Low spin tetrahedral complexes are not known.
Write the anode and cathode reactions and the overall cell reaction occurring in a lead storage battery during its use.
Account for the following:
Conductivity of CH\(_3\)COOH decreases on dilution.
Which vitamin is responsible for the coagulation of blood?
Which one of the following is a disaccharide?
\[ \text{Glucose, Lactose, Amylose, Fructose} \]
What is the difference between native protein and denatured protein?
Give plausible explanation for each of the following:
Amides are less basic than amines.
Give plausible explanation for each of the following:
Aromatic primary amines cannot be prepared by Gabriel Phthalimide synthesis.
Arrange the following compounds in increasing order of their boiling point:
\[ \text{(CH}_3\text{)}_2\text{NH, CH}_3\text{CH}_2\text{NH}_2, \text{CH}_3\text{CH}_2\text{OH} \]
How do you convert:
2-Bromobutane to but-2-ene
How do you convert:
Propene to 1-Iodopropane
How do you convert:
Chlorobenzene to biphenyl
Draw the structure of the major monohalo product for each of the following reactions:
phenol
Draw the structure of the major monohalo product for each of the following reactions:
methylbenzene
Using \( E^\circ \) values of X and Y given below, predict which is better for coating the surface of iron to prevent corrosion and why?
Given: \( E^\circ_{X^{2+}/X} = -2.36 \, \text{V} \) \( E^\circ_{Y^{2+}/Y} = -0.14 \, \text{V} \) \( E^\circ_{Fe^{2+}/Fe} = -0.44 \, \text{V} \)
State the following:
Faraday’s first law of electrolysis
State the following:
Kohlrausch law of independent migration of ions
Phenols undergo electrophilic substitution reactions readily due to the strong activating effect of the OH group attached to the benzene ring. Since the OH group increases the electron density more to the ortho- and para- positions, one of the examples of the aldehyde group being introduced on the aromatic ring of phenol, ortho to the hydroxyl group. This is a general method used for the ortho-formylation of phenols.
Answer the following questions:
Read the passage carefully and answer the questions that follow.
Passage: The rate of a chemical reaction is expressed either in terms of decrease in the concentration of reactants or increase in the concentration of a product per unit time. Rate of the reaction depends upon the nature of reactants, concentration of reactants, temperature, presence of catalyst, surface area of the reactants and presence of light. Rate of reaction is directly related to the concentration of reactant. Rate law states that the rate of reaction depends upon the concentration terms on which the rate of reaction actually depends, as observed experimentally. The sum of powers of the concentration of the reactants in the Rate law expression is called order of reaction while the number of reacting species taking part in an elementary reaction which must collide simultaneously in order to bring about a chemical reaction is called molecularity of the reaction.
 Answer the following questions:
The elements of 3d transition series are given as: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn
Answer the following:
The role of a catalyst is to change _____________ .
Why is [Ni(CN)4]2- square planar while [Ni(CO)4] is tetrahedral? [Atomic number : Ni = 28]