List of top Chemistry Questions asked in CBSE CLASS XII

Give equations of the following reactions:(i)Oxidation of propane-1-ol with alkaline KMnO4 solution.
(ii)Bromine in CS2 with phenol.
(iii)Dilute HNO3 with phenol.
(iv)Treating phenol with chloroform in the presence of aqueous NaOH

Explain how does the –OH group attached to a carbon of benzene ring activate it towards electrophilic substitution?

Write the important structural and functional differences between DNA and RNA.
What is the difference between a nucleoside and a nucleotide ?

Give two reactions that show the acidic nature of phenol. Compare the acidity of phenol with that of ethanol.
The acidic nature of phenol can be represented by the following two reactions:

What are nucleic acids ? Mention their two important functions.
The partial pressure of ethane over a solution containing \(6.56 × 10^{–3} g\) of ethane is 1 bar. If the solution contains \(5.00 × 10^{–2} g\) of ethane, then what shall be the partial pressure of the gas?

Write the IUPAC names of the following ketones and aldehydes. Wherever possible, give also common names. 
\((i) CH_3CO(CH_2)_4CH_3 \)
\((ii) CH_3CH_2CHBrCH_2CH(CH_3)CHO \)
\((iii) CH_3(CH_2)_5CHO \)
\((iv) Ph-CH=CH-CHO\)
\((v)\)
\((vi) PhCOPh\)

Define the following as related to proteins (i)Peptide linkage (ii)Primary structure (iii)Denaturation.

You are given benzene,conc.H2SO4 and NaOH.Write the equations for the preparation of phenol using these reagents.

What are the common types of secondary structure of proteins ?
State Henry’s law and mention some important applications?
Write the mechanism of hydration of ethene to yield ethanol
Why do gases always tend to be less soluble in liquids as the temperature is raised?
Differentiate between globular and fibrous proteins.

Give the equations of reactions for the preparation of phenol from cumene.

While separating a mixture of ortho and para nitrophenols by steam distillation, name the isomer which will be steam volatile. Give reason.

What are enzymes ?

Give the structures and IUPAC names of monohydric phenols of molecular formula,C7H8O.

What is meant by hydroboration-oxidation reaction?Illustrate it with an example.

What is the effect of denaturation on the structure of proteins ?
How are vitamins classified ? Name the vitamin responsible for the coagulation of blood.

Alcohols are comparatively more soluble in water than hydrocarbons of comparable molecular masses. Explain this fact.

Name the following compounds according to IUPAC system of nomenclature: 
\((i) CH_3CH(CH_3)CH_2CH_2CHO \)
\((ii) CH_3CH_2COCH(C_2H_5)CH_2CH_2Cl \)
\((iii) CH_3CH=CHCHO \)
\((iv) CH_3COCH_2COCH_3 \)
\((v) CH_3CH(CH_3)CH_2C(CH_3)_2COCH_3 \)
\((vi) (CH_3)_3CCH_2COOH \)
\((vii) OHCC_6H_4CHO-p\)

Why are vitamin A and vitamin C essential to us ? Give their important sources.